بسم اﷲ الرحمن الرحيم [601862]

بسم اﷲ الرحمن الرحيم

قالوا سبحانك ال علم لنا إال ما علمتنا إنك أنت العليم
الحكيم

صدق اهلل العظيم
سورة البقرة (آيت ٣٢)

Effect Of Coloring Technique And External
Surface Treatment On Esthetic Outcome Of Full –
Contour Zirconia Restorations
Thesis
submitted for the partial fulfillment
of the Dectorate Degree requirements in Fixed Prosthodontics ,
Faculty of Dentistry, Ain Shams University .

By
Sara Mahanny Ibrahim Sobieh F oudah
B.D.Sc (Ain Shams University, 2005)
M.D.Sc. (Ain Shams University, 2011)
Assistant lecturer of Fixed Prosthodontics
Crown and Bridge Department
Faculty of Dentistry ,Ain Shams University.

Faculty of Dentistry
Ain Shams University
2015

Supervisors

Dr. Tarek Salah Morsi
Assistant Professor of Fixed Prosthodontics
Head of Crown and Bridge Department
Faculty of Dentistry, Ain Shams University.

Dr. Amr Saleh El-Etreby
Lecturer of Fixed P rosthodontics.
Crown and Bridge Department
Faculty of Dentistry, Ain Shams University.

Dedication
To my father, the source of strength and support from the
early start…
To my mother, the greatest gift I had ever got from God, her
name is another name for giving and love…
To my lovely understanding husband, holding my hands and
lifting me up all the time..
To my sister, the ang el with the precious heart…
To my brother, my soul mate…
To my best friend, for always being there for me…
And finally to my beloved daughter and son ,
"I'm filled with l ove and appreciation to all of you , wish I could
make you proud of me".

Acknowledgement
I am greatly honored to express my heartful thanks and
deep gratitude to Dr.Tarek Salah Morsi, Assistant Professor of
Fixed Prosthodontics and Head of Crown and Bridge
Department, Ain Shams University, for his valuable guidance
and support throughout this work. I benefited greatly from
his experience and knowledge.
I would like to express my deepest gratitud e to Dr . Gihan
Farouk Younis, Professor of Fixed Prosthodontics, Ain Shams
University, for her meticulous advice and valuable comments .
I would like to express my deepest gratitude to Dr. Amr
Saleh El -Etreby , Lecturer of Fixed Prosthodontics , Ain Shams
University, for his meticulous advice and valuable comments .
Special thanks to Professor Dr. Mohamed Shafik Khalil ,
Professor of Photometry, Radiometrey and Colorimetry
Department, at National Institute for Standards (NIS Egypt) ,
who through h is great and highly appreciated effort the
laboratory spectrophotometry was accomplished, he was
generous with time and effort.
My heartful thanks and appreciation to Dr. Ayman Galal
Eldimeery, Lecturer of Fixed Prosthodontics, Ain Shams

University, for bein g a worthy role model and a teacher to
always follow and consult.
Finally, I would like to thank all the staff members,
colleagues and laboratory technicians for their help and
encouragement during the course of this work.

Contents

List of Table s ………………………….. ………………………….. . i
List of Figures ………………………….. …………………………. ii
Introduction ………………………….. ………………………….. . 1
Review of Literature ………………………….. ………………… 3
Aim of T he Study ………………………….. …………………… 35
Materials and Methods ………………………….. ………….. 36
Results ………………………….. ………………………….. ……. 62
Discussion ………………………….. ………………………….. .. 83
Summary and Conclusions ………………………….. ………. 94
References ………………………….. ………………………….. . 98
Appendix
Arabic Summary

i
List Of Tables
TABLE 1: SUMMARY OF LITERATUR E RELEVANT TO PERCEPTIBILITY AN D ACCEPTABILITY
TOLERANCE ………………………….. ………………………….. ………………………….. …….. 6
TABLE 2: STANDARD COMPOSITION OF IN CORIS TZI. ………………………….. …………………… 36
TABLE 3: SAMPLES GROUPING . ………………………….. ………………………….. ……………….. 39
TABLE 4: FIRING CHART OF VITA AKZENT GLAZE ………………………….. ……………………. 49
TABLE 5 :DESCRIPTIVE STATISTIC S AND RESULTS OF COM PARISON BETWEEN (ΔE) AFTER USING
THE TWO COLORING TEC HNIQUES TTHE ………………………….. ………………………….. .. 63
TABLE 6: DESCRIPTIVE STATISTIC S AND RESULTS OF COM PARISON BETWEEN (ΔE) WITH
DIFFERENT SURFACE TR EATMENTS ………………………….. ………………………….. …….. 65
TABLE 7: DESCRIPTIVE STATISTIC S AND RESULTS OF COM PARISON BETWEEN (ΔE) BEFORE AND
AFTER AGING ………………………….. ………………………….. ………………………….. …. 66
TABLE 8: DESCRIPTIVE STATISTIC S AND RESULTS OF COM PARISON BETWEEN TP AFTER USING THE
TWO COLORING TECHNIQ UES. ………………………….. ………………………….. …………… 68
TABLE 9: DESCRIPTIVE STATISTIC S AND RESULTS OF COM PARISON BETWEEN TP WITH DIFFERENT
SURFACE TREATMENTS . ………………………….. ………………………….. …………………. 70
TABL E 10: DESCRIPTIVE STATISTIC S AND RESULTS OF COM PARISON BETWEEN TP BEFORE AND
AFTER AGING . ………………………….. ………………………….. ………………………….. … 71
TABLE 11: DESCRIPTIVE STATISTIC S AND RESULTS OF COMPARISO N BETWEEN OP AFTER USING
THE TWO COLORING TEC HNIQUES . ………………………….. ………………………….. …….. 73
TABLE 12: DESCRIPTIVE STATISTIC S AND RESULTS OF CO MPARISON BETWEEN OP WITH
DIFFERENT SURFACE TR EATMENTS . ………………………….. ………………………….. ……. 75
TABLE 13: DESCRIPTIVE STATISTIC S AND RESULTS OF COM PARISON BETWEEN OP BEFORE AND
AFTER AGING . ………………………….. ………………………….. ………………………….. .. 76

ii
List of Figures
FIGURE 1: INCORIS TZI BLOCK ………………………….. ………………………….. ……………….. 36
FIGURE 2: INCORIS TZI COLORING LIQUID ………………………….. ………………………….. …… 37
FIGURE 3: VITA AKZENT GLAZE AND FLUI D ………………………….. ………………………….. .. 37
FIGURE 4: ZI-POLISH ZIRCONIA POLIS HING PASTE . ………………………….. ……………………… 38
FIGURE 3: MICRACUT 150 PERCISION CUTTER . ………………………….. …………………………. 40
FIGURE 3: THE BUILT -IN DIGITAL MICROMETE R. ………………………….. ……………………….. 41
FIGURE 7: SPEED ADJUSTER . ………………………….. ………………………….. …………………. 41
FIGURE 8: MONOLITHIC ZIRCONIA P LATE . ………………………….. ………………………….. …… 42
FIGURE 9: VERIFIED THICKNESS WI TH DIGITAL MICROMETE R. ………………………….. …………. 42
FIGURE 11: INCORIS TZI COLORING LIQUID A2 AND DIP TANK ………………………….. ……… 43
FIGURE 11: INCORIS TZI COLORING LIQUID BRUS HED TO THE SURFACE ………………………….. 44
FIGURE 12: SIRONA IN FIRE HTC SPEED FURNACE ………………………….. ………………………. 45
FIGURE 13: SINTERING BOAT SHOWIN G ZIRCONIA DISCS ON SINTERING BEADS …………………… 45
FIGURE 14: SHRINKAGE OF ZIRCONIA DISC AFTER SINTERING ………………………….. …………. 46
FIGURE 15:V ERIFICATION OF THICK NESS AFTER SINTERING . ………………………….. …………… 46
FIGURE 13: ENVIROMENTAL SCANNING ELECTRON MICROSCOPE (ESEM). ……………………. 47
FIGURE 17:G LAZE IS BRUSHED ON T HE SAMPLE 'S SURFACE ………………………….. ……………. 48
FIGURE 18: GLAZED SAMPLES INSIDE THE FIRING FURNACE ………………………….. ……………. 49
FIGURE 14:K0262 DIALITE ZR INTRA -ORAL ADJUSTMENT FINIS HING AND POLISHING S YSTEM 50
FIGURE 61: ZI-POLISH PASTE WITH WHEEL BRUSH RODEO ………………………….. …………… 50
FIGURE 21: GREEN COURSE GRINDER (LD11CZR). ………………………….. …………………….. 51
FIGURE 22: GREEN MEDIUM POLISHIN G POINTS FOR PRE -POLISHING (W 16-17-18 MZR MED). . 51
FIGURE 23: ORANGE FINE POLISHING POINTS FOR HIGH LUST ER (W 16-17-18 FZR FINE) . ……. 52
FIGURE 69: ZI-POLISH DIAMOND POLIS HING PASTE APPLIED W ITH WHEEL BRUSH RODEO . ……. 52
FIGURE 63: VITA EASYSHADE COMPACT ………………………….. ………………………….. ….. 54
FIGURE 63: THE TIP OF VITA EASYSHADE COMPACT OVER THE SAMP LE DURING MEASUREMEN T.
………………………….. ………………………….. ………………………….. …………………. 55
FIGURE 67: VITA EASYSHADE COMPACT SHOWED ΔE FROM THE SELECTED SHADE A2 ………. 55

iii
FIGURE 63:CARY 5000 UV–VIS–NIR SPECTROPHOTOMETER . ………………………….. ……….. 57
FIGURE 64: SAMPLE INSIDE SPECTRO PHOTOMETER ………………………….. ……………………. 58
FIGURE 31: SAMPLES READY FOR SCA N ………………………….. ………………………….. …….. 59
FIGURE 31:MIDMARK M11 ULTRACLAVE AUTOCLAVE . ………………………….. ………………. 60
FIGURE 36: SAMPLES INSIDE AUTOC LAVE . ………………………….. ………………………….. ….. 61
FIGURE 33: BAR CHART REPRESENTIN G MEAN (ΔE) AFTER USING THE TWO COLORING
TECHNIQUES ………………………….. ………………………….. ………………………….. ….. 64
FIGURE 34:B AR CHART REPRESENTIN G MEAN (ΔE) WITH DIFFERENT SURFA CE TREATMENTS ….. 65
FIGURE 35:B AR CHART REPRESENTIN G MEAN (ΔE) BEFORE AND AFTER AGI NG. …………………. 67
FIGURE 36: BAR CHART REPRESENTIN G MEAN TP AFTER USING THE TWO COLORING TECHNIQUES .
………………………….. ………………………….. ………………………….. …………………. 69
FIGURE 37: BAR CHART REPRESENTIN G MEAN TP WITH DIFFERENT SURFA CE TREATMENTS . …… 70
FIGURE 38: BAR CHART REPRESENTIN G MEAN TP BEFORE AND AFTER AGING . …………………… 72
FIGURE 39:B AR CHART REPRESENTIN G MEAN OP AFTER USING THE TWO COLORING TECHNIQUES .
………………………….. ………………………….. ………………………….. …………………. 74
FIGURE 40: CHART REPRESENTING M EAN OP WITH DIFFERENT SURFA CE TREATMENTS . ………… 75
FIGURE 41: BAR CHART REPRESENTIN G MEAN OP BEFORE AND AFTER AGI NG. ………………….. 77
FIGURE 96: ESEM IMAGE X 500 OF COLORED ZIRCONIA ………………………….. ………………. 78
FIGURE 93: ESEM IMAGE X 500 OF GLAZED ZIRCONIA S URFACE BEFORE AGING . ………………. 78
FIGURE 99:ESEM IMAGE X 500 OF GLAZED ZIRCONIA S URFACE AFTER AGING . …………………. 78
FIGURE 93: ESEM IMAGE X 500 OF POLISHED ZIRCONIA SURFACE . ………………………….. ….. 78
FIGURE 93: ESEM IMAGE X 500 OF POLISHED AND GLAZ ED ZIRCONIA SURFACE . ……………….. 78

Introduction

1
btaining monolithic all-zirconia restoration truly expand ed the extension of
zirconia application and eliminate d the most common reported mode of
failure related to its veneering necessity to optimize esthetics (1). The ability of
such a restoration to match the color of the surrounding dentition is an integral
part of its success. In a 1984 survey, Goldstein and Lancaster found that of
subjects who were dissatisfied with their smiles, the predominant complaint was
tooth color (2). The ability to match a ceramic crown with the surrounding
dentition is a consistent problem in clinical dentistry. Prospective and
retros pective clinical studies have documented between 44% and 63% color
mismatch of cemented ceramic crowns (3-6).
Industrial, technical and clin ical attempts to duplicate true to life all -ceramic
restoration ha ve been evident during last decades. Industrial attempts are
successive through controlling processing facilities that have its impact on the
material microstructure and consequently the way it modifies or interacts with
light. Controlling of; grain size, cr ystalline content, difference in refractive
indexes between crystals and matrix plus amount of voids and porositie s (7)
through multiple processing parameters, such as different sintering conditions (8),
is a non -stop process that aimed to provide wide variety of materials suit for
different esthetic indications. Industrial facilities were behind the revolution of
nano -structured polycrystalline zirconia in an attempt to add esthetic value to the
mechanical supremacy.
Technical control through choosing the material that fits the needed demand,
its correct handling , coloring and finishing is the second step for esthetic
optimization and excellence. Finally, the clinician – by whom the whole process
starts and ends – with his basic thorough and updated knowledge about the
industrial and technical improvement can wisely calculate all the interactions to
reach the target esthetics and patient satisfaction. o

Introduction
2
Determination of the color of teeth and porcelai n crowns can be described by
the ―double layer effect‖. This means that the resulting color appears from a
diffuse reflectance of the inner dentin or opaque porce lain layer filtered by the
scattering of outer translucent layer (9). Therefore, interactions of the optical
scattering and absorption co efficients, thick ness of the outer translucent material,
and reflectance of the background substructure, can influence the changes of
over-all color parameters (10). Numerous optical properties as a result of this
interaction are created to form the final image of a tooth or a restorati on. Besides
the three dimensions of the color ( value, chroma and hue), other optical
phenomenon such as; translucency, opalescence, fluorescence and iridescence
can‘t be ignored when life-like appearance is targeted (11). In contrast to the
double layer concept that have been best imitated though layered restorations , the
creation of esthetic monolithic zirconia restorations could be challenging since
they are full -contour mono block restorations.
Although monolithic zircon ia restorations have been intro duced in dentistry,
there have been few studies reporting the standard way of handling to optimize
their optical properties at a clinically rel evant thickness. Furthermore, there is no
standardization of coloring or finishing techniques regarding color duplication ,
translucency and opalescence parameters of the monolithic zirconia restorations.
Aging with its non -negligible structural effect on the material (12) had vague effect
on esthetic outcome up to date.
This study was designed to assess the effect of coloring technique, surface
finishing and aging on esthetic outcome in terms of shade reproduction,
translucency and opalescence of monolithic zirconia .

Review Of
Literatu re

3
erfection of esthetic outcome of a dental restoration is a trial for
duplicating a dynamic situation of live interaction between light
wavelengths and the tooth structural tissues (either by; reflection, absorption,
transmission and/or scattering ) to produ ce the very unique spectral data perceived
by the observer and translated into optical attributes that represent the final
appearance.
Color being one major attribute to the final optical appearance was always
searched in a way to translate it to numerical data for industrial perfection ,
repeatability and predictability. In early 1900’s Munsell Color System was the
first attempt to organize colors according to its three par ameters of: value, hue
and chroma (13). Followed by Commission International de l‘Eclairage (CIE)
published the first standards for color matching, establishing some scientific
parameters for color evaluation (14).
The paper from Clark 1933 (15), based mainly on the Munsell color scale of
1905 , was the first attempt to organize dental colors. In 1950s , the first dental
shade guides based on a rational arrangement of shade tabs were introduced to
the dental profession and, even if still based on individual perception rather than
on strict scientific criteria, they were rapidly adopted by clinicians. Sproull in the
early 1970s (16), (17) published a series of articles in which the three dimensional
nature of color and its relationship with dental shades was studied, and a series of
theoretical and practical indications were given in order to improve color
matching in dentistry. These articles, that represented for a long time the ―state of
the art ‖ for dental color matching, pointed out how the procedure for shade taking
was negatively influenced by several factors, among which shade guides that
were regarded as poor and inadequate in relation to the complexity of the
appearance of the teeth. P

Review of Literature
4
Based on Munsell system and even CIE specifications of 1931 an irregular
space distribution was found , resulted in differences between calculated and
perceived color differences, and for this reason it was clear that a new system for
color measurement was required . In1976 and 1978 the CIE developed a new
system, called CIE Lab* (18), (19), in which for the first time it was possible to
express color by numbers and calculate the differences between two colors in a
way that corresponded to visual perception. In this system, which is regarded as
the benchmark for scientific purposes, color is expressed by three coordinates:
L* value is the degree of lightne ss of an object,
a* value is the degree of redness/greenness, and
b* value is the degree of yellowness/blueness.
The CIE Lab* system was scientifically based and useful for calculating
color differences, but not amenable to easy color communication. For color
communication, the HSB/HSV (Hue; Saturation or Chroma; Brightness or
Lightness or Value) system was most commonly used, even in dentistry. In this
system, H (Hue) is defined as the radial component of the cylindrical coordinates
CIELab* and calculate d according to the formula ;
hab = arctan ( b*/a*);
S or C (Saturation or Chroma) is defined as the radial component of the
cylindrical coordinates CIE Lab* and calculated according to the formula ;
Cab = [(a*)2 + (b*)2]1/2;
L (Lightness or Brightness or Value), corresponds to the L* of the CIE Lab*
system and represents the lightness -darkness of a color.
In the CIE Lab* system a formula is used to calculate color differences:

Review of Literature
5
ΔEab = [(L 1 − L 2)2 + (a 1 − a 2)2 + (b 1 − b 2)2] ½.
This was pivotal turning point in color matching field. As instruments like
colorimeters and spectrophotometers were quickly developed and improved to
measure color and color differences (20), (21). Although , color matching in dental
practice did not benef it immediately from these developments and visual
assessment was still considered to be the best approach . But it was the starting
point.
Moreover, nearly solid numerical relations can correlate to clinical relevance
of such numerical difference. Numerous studies were performed to translate the
ΔE valu e to a clinically relevant data (20-28). Despite much effort, the identification
of a ΔE value for the ―clinically perceptible and acceptable differences ‖ is a very
difficult task . Perceptibility level is defined by the color difference that is
perceived by 50% of skilled observers although is acceptable , whereas
acceptability level is the mean color difference at which 50% of skilled observers
will reject color, considering it unac ceptable mismatch(22),(26). Reviewing
literature revealed a range of perceptibility and acceptability not a single point,
that is may be due to different testing environments and materials and subjective
nature of color perceiving, it can be summarized in the following table; (Table 1 .
pg:6).
In 2004 the specification for measurement of color differences was upgraded
by the CIE (29) and an improvement of the ΔE ab formula was proposed. This new
formula is defined CIEDE2000 as ΔE 00:
ΔE00 = {[ΔL `/(kLSL)]2 + [ΔC`/(kCSC)]2 + [ΔH `/(kHSH)]2 +RT[ΔC `/(kCSC)] ×
[ΔH`/(kCSC)]}1/2

Review of Literature
6
Table 1: summary of literature relevant to perceptibility and acceptability tolerance
Perceptibility Study ΔE Acceptability Study ΔE
Douglas and Brewer 1998 (20) 0.4 Douglas and Brewer 1998 (20) 1.7
Kuehni and Marcus 1979 (21) 1.0 Ragain and Johnston 2000 (22) 2.72
Vichi et al 2004 (23) 1.0 Vichi et al 2004 (23) 3.3
Ishikawa and Nagai 2009 (24) 1.6 Ruyter et al 1987 (25) 3.3
Seghi et al 1989 (26) 2 Douglas et al 2007 (27) 5.5
Douglas et al 2007 (27) 2.6 Johnston and Kao 1989 (28) 6.8
Johnston and Kao 1989 (28) 3.7

This new formula has been developed in order to introduce weighing
functions ( SL, SC and SH) and parametric factors (kL, kC and kH) to allow for
differences in texture, background, separations, etc for the lightness, chroma and
hue components, respectively. The aim was to improve the correlation between
visually perceived differ ences and calculated differences. Literature reported that
the CIEDE200 0 color difference formula provided a better fit than the CIE Lab*
formula in the evaluation of color difference threshold of dental ceramics (30-32).
Notwithstanding , the possible beneficial use of this improved formula, most of
the papers recently published in the dental literature still refer to ΔEab. This is
probably due to the relative complexity of the ΔE00 formula, as well as to the
ease of comparison with earlier studies, even if the transformation of L*a*b* into
L`a`b` is just a matter of ari thmetics (33), (34) .
To minimize subjective nature of human eye and variables of lighting
conditions that may cause some variations in recording shades , and phenomenon
such as metamerism can be expressed; digitalizing this proce ss through shade
taking devices developed as new generations of colorimeters and
spectrophotometers was applied to the dental field (26). These devices range from

Review of Literature
7
software that can be used in conjunction with images taken with a digital camera,
to colorimeters and spectrophotometers, in some cases combined with an imaging
system (35).
Evident supremacy for spectrophotometers is proved in literature (36-38). A
33% increase in accuracy compared to human eye and conventional techniques,
and a more objective match in 93.3% of cases was reported (36). They measure the
amount of light energy reflected from an object at 1 –25 nm intervals along the
visible spectrum , thus registering the exact spectral reflectance data (39), (40). A
spectrophotom eter contains a source of optical radiation, a means of dispersing
light, an optical system for measuring, a detector and a means of converting light
obtained to a signal that can be analyzed . The data obtained from
spectrophotometers must be manipulated a nd translated into a form useful for
dental professionals. The measurements obtained by the instruments are
frequently keyed to dental shade guides and converted to shade tab equivalent (41).
One of the best rated benchmark instrument is the VITA Easyshade
Compact (Vita Zahnfabrik, Bad Sackingen, Germany), released in 2009 as an
evolution of the former Easyshade ., it is cordless, small, portable, cost efficient,
battery operated, contact -type spectrophotometer that provides shade information
to help aid in the color analysis process. It is engineered relying on large diameter
fiber optics arranged in a specific pattern in a stainless steel probe of 5-mm
diameter that can both illuminate a tooth and receive light that is internally
scattered by the enamel layer and reflected from the dentin layer of the tooth (42).
Due to the array of light fibers, Different measurement modes are possible with
Easyshade Compact: tooth single mode, tooth area mode (cervical, middle and
incisal shades ), restoration color verification ( provides ΔE values and includes
lightness, chroma and hue comparison) and shade tab mode (practice/training
mode) (42).

Review of Literature
8
Browning et al 2009 (43) reported that the Easyshade device, when
compared for accuracy and consistency to three experienced clinicians, was at
least comparable if not better than the dentist. In particular, the degree of
matching was 91% for Easyshade and 69%, 85% and 79% for the three
clinicians, respectively. Kim -Pusateri et al 2009 (44) reported accuracy of 93%
for Easyshade also. It should be noted that the results seemed to improve with
time (35).
However color is not the only optical attribute and matching shade per se
could not guaranty duplicate and true to life appearance. Other optical attributes
are rather important for maximum perfection in esthetic outcome ; translucency,
opalescence, fluorescence and iridescence are optical properties related to dental
tissues‘ unique way in modulating incident light (34).
Translucency is very importa nt optical property and was described as the
forth color parameter by many authors (45). Translucency can be described as a
state between complete opacity and transparency (46). As some authors referred to
it as t he property of a material by which a major portion of the transmitted light
undergoes scattering (34) , (47), other s considered translucency to be the amou nt of
light transmi ssion through the object or diffuse reflectance from a substrate
surface through a turbid medium (48). The translucency of dental ceramic systems
depends on their thickness, their scattering and absorption coefficients, grain size
especially in relation to size of light wavelength, crystalline content, matching in
refracti ve indexes, amount of voids, porosities and pigments (49).
The translucency of a material can be measured as percent of diffuse and
direct transmitted light (total transmission T%) that represents absolute
translucency which is more difficult to measure necessitates use of dual beam,
integrating sphere radiom eter or spectrophotometer able to capture all of the light

Review of Literature
9
transmitted through a specimen in comparison to the intensity of light from a split
beam (47).
Easier relative translucency can be measured either through ; contrast ratio
(CR) (50) , (51) which is the ratio between the reflectance (Y) of a specimen over a
black background (b) to that over a white background (w) of a known reflectance
CR = Y b/Yw where value of a totally opaque material is 1, while the value of a
totally transparent material is 0. Or through employing the translucency
parameter (TP) (49) , (52) which was first described by Johnston et al . 1995 and
used to describe translucency of dental materials (52), defined as the color
difference of a material of a given thickness over white and black backgrounds,
and corresponds directly to common visual assessments ;
TP= [(L b* – Lw*) 2 + (a b* – aw*) 2 + (b b* – bw*) 2 ]1/2
Where TP va lue of zero corresponds to a completely opaque material and the
greater the TP value the higher the actual transl ucency of the material. Despite of
these studies, there is no standard or consensus on the method of choice to
quantify translucency of aesthetic restorative materials (53).
Opalescence is closely related to the translucency . As for opalescence
feature, there should be a light scattering of shorter wavelengths of the visible
spectrum in a translucent material. These redirected shorter wavelengths inside
the material can be reflected again through the surface increasing the amount of
reflected light and ad ding brightness and vitality to the tooth (54). The enamel
selectively pass longer wavelength in yellow red region and scatters the shorter
wavelength in blue violet range . This selective filtration is related to nature of
enamel structure in which hydroxy apetite crystals existed with same size of blue
light short wavelength , causing scattering of wavelength s in this range while

Review of Literature
10
allowing longer wavelength to pass unobstructed (54). Thus i t appears blue in
reflected light and orange -yellow in transmitted lig ht (55), (56) .
The opalescence parameter (OP) was calculated as the d ifference in yellow –
blue and red -green coordinates between the transmitted and reflected colors using
the following equation (57);
OP = [(CIE a ∗T− CIE a∗R)2+ (CIE b∗T− CIE b∗R)2]1/2
where subscript T refers to the transmitted color and subscript R refers to the
reflected color over a black background.
Nano -structured Yettrium stabilized tetragonal zirconia
polycrystalline materials availabl e as monolithic zirconia (MZ) have well
proven evidence -based excellent mechanical behavior (58), (59). This excellence is
mainly due to two reasons; the first referred to the well known unique
transformation toughness mechanism seen with its predecessor. The second cause
is related to the elimination of the need to a veneering process that was always
been the week -link behind the most common cause of failure in zirconia -based
restorations (60), (61). Very high failure rates were recorded in literature concerning
veneer chipping ; the highest percentage was reported by Raigrodski et al 2006
(62) as 25% after a mean follow -up of 2 years and 6 months. This is followed by
15% veneer chipping after 2 years follow -up reported by Vult v on Steyern et al
2005 (63), similar percentage was reported by Sailer et al 2007 (64) (15.2% veneer
chipping) after a lo nger mean service time of 3 years (±13.8 months). Although
the literature may report decreasing failure rates -with trials to improve zirconia
veneer bond – below 10% with 1,4 and 5 years follow up (65-69), it is still far away
from the ceramometallic gold standard that exhibited a failure rate of 0.4% for
single -tooth metal -ceramic restorations and 2.9% for FPDs after 3 years as
reporte d by Pjturson BE et al 2007 (70), Sailer et al 2007 (71) respectively .

Review of Literature
11
Esthetic outcome of this material as a monolithic restoration is of great
concern, yet had not been studied enough in literature;
1. Chemical Nature and Esthetic Outcome:
Traditional ZrO 2-Y2O3 system for high strength and high toughness materials
consists mainly of single tetragonal phase with fine and uniform grains of critical
size between (1 -0.2 µm) that is equal to (1000 -200 nm), with crystalline content
of 98% -99.5%, and containin g approximately 3 mol% Y 2O3 as the dopant or
stabilizer (72). Both unalloyed and stabilized forms of zirconia have a high
refractive index (RI = 2.1-2.2) just ifying their use as opacifiers in other materials
(73). This system with its high crystalline conte nt, grain size in the same range or
larger than light wavelengths , high RI and low absorption coefficient resulted in
maximum scattering with high opacity in the visible and infrared regions of the
spectrum with white to ivory color (73). Measuring the ang ular scattering
distribution of zirconia samples by Oliveras A et al 2012 (74) show ed that
sintered zirconia result ed in optical behavior more similar to those of dentine
tissue, in terms of scattering anisotropy (74).
Many studies revealed a maximum opaci ty for zirconia reaching that of
metals use d in metal -ceramic restorations , Heffernan et al 2002 (7)and Chen et
al 2008 (75) reported in two different studies a CR of 1 (equal to that of metal) for
two different ziconia system s in the thickness of 0.5 mm , these results justifying
the use of zirconia for maski ng underlying structures and contraindicating its use
without esthetic veneer whenever esthetics and translucency is of prime concern.
Other studies repo rted less opacity or a certain degree of translu cency even if
not remarkable; a CR of 0.88 was reported by Spyropoulou et al 2011 (76) for
shaded zirconia cores of 0.6 mm thickness with a difference significantly greater

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12
than 0.07 than that of metal , which is quite perceptible to the human eye in terms
of more translucency as reported by Liu et al 2010 (77) considering a ΔCR of 0.07
to be the perceptible threshold for human eye. Besides a total luminous
transmittance of disc shaped zirconia specimens of 0.5 mm thickness was reported
by Luo and Zhang 2010 (78) to be 2.29±0.06%. Baldissara et al 2010 (79)
assessed translucency of 4 types of zirconia core s measured a range of total
transmittance reaching 3.57 % with the highest translucent material in this study
being LAVA of 0.3 mm thickness, the authors claimed that this type of zirconia
at this thickness can reach 71.7% of the translucency of one of glass ceramics
used as a control (IPS emax press) .
Reducing grain size below the range of visible light wave length was thought
to increase the in -line transmittance of light ins ide the structure, accordingly
many traditional ceramic materials showed interesting optical properties when the
grain size of sintered ceramic was nanosized (80). Modifications in manufa cturing
proces ses and sintering conditions were tried to obtain the nano -sized grains in
zirconia thus adding esthetic excellence to the supreme mechanical quality.
Wang et al 2011 (81) tested different sintering heating rates on microstructure
and resulte d translucen cy, highest heating rate tested resulted in a microstructure
dominated by 230 nm sized particles, smaller than the shortest visible
wavelength, which became less dominating with decreasing the heat rate.
Meanwhile, the highest total transmissio n and translucency measured in terms of
CR were recorded for the highest heating rate with value of 35.29% T and 0.68
respectively. However, the lowest total transmission was 28.44% and maximum
CR was 0.77 that still represented improvement in zirconia tra nslucenc y
compared with previous ly mentioned studies testing zirconia with micrometric
microstructure.

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13
Very recently, Krell and coworkers 2011 (82) propose d a model based on
Mie theory to quantitatively describe the scattering behavior in Y -TZP. This
model points out that the in -line transmittance of 50% at the visible wavelength
range is expected as the grain size <40 nm for a pore -free Y -TZP with 1mm
thickness (82). This can account for the previous experimental results of the low
transparency of Y-TZP, since such fine grains are not attained. On the other hand,
this model reveals the weak birefringent scattering in the infrared (IR) range as
grain sizes less than 200 nm . Nanometric (115 nm) dense tetragonal ZrO2 was
fabricated by Klimke et al 2011 (82). using hot isotropic pressing (HIP). The
0.5mm thickness specimen exhibited the maximum theoretical value of in -line
transmittance (77%) in the IR region of 4 -5 μm. Zhang et al 2011 (83) prepared
nanograined (80 nm) dense tetragonal zirconia using high -pressure spark plasma
sintering (HP -SPS). Inline transmittance of a 1.5mm thick sample approached
81–87% of the theoretical value in the wavelength of 3 –5 μm.
A significant lower light transmittance reported by Jiang et al 2011 (84) for
(90-40nm) sized zirconia grains . This may be referred to the difference in method
of sintering. Although 40nm sized type revealed significantly higher
transmittance than that of the 90nm sized type. The effect of sintering
temperature was different as well, signifi cant enhancement for transmittance was
observed for the 90nm sized group with increasing the sintering temperature
while this effect was not significant for the 40nm sized group.
A size of 50nm for 3mol % YTZP system was obtained in two different
studies (85), (86) in 2007 and 2008 using very similar densification methods
utilizing high pressure and electric current . Translucency was evident in both
studies measured in one of them to reach 50% transmittance in the near infra red
for 1mm thick sample.

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14
A uniq ue novel nano -structured YTZP system was patented in 2011 with a
grain size of 3 -5 nm, developed by a method for producing non -agglomerated 3
nm nanocrystalline zirconia powder using a revolutionary bottom -up
nanotechnology technique known as "gas -phase condensation ‖ (87) . The
manufacturer claimed that above 50% of light transmittance was obtained for a
thickness of 0.6 mm, even 1mm thickness of shaded type allowed above 45%
transmittance (88).
While particle size appeared to have strong correlation with the resulte d
translucency, many studies (79) , (85) pointed out that it was not the controlling
factor, or it might be one factor among many others that directly affect the
material ‘s light absorption , diffusion and scattering pattern . Baldissara et al
2010 (79) claimed that ―necessary conditions for a translucent ceramic are that it
does not absorb radiation in the visible spectrum (0.4 -0.7µ) and light diffusion is
reduced to a minimum‖. Various causes of diffusion within polycrystalline
ceramic materials include; irregularities in the distribution of the phases, defects
and voids at grain boundaries, optical anisotropy, grain size larger than the light
wavelength, different refractive indexes among particles , and the chemical nature
all of those may increa se light scattering. The authors referred the increased
opacity of one type of tested zirconia cores (although it was not the highest in
thickness and the grain size was small enough of 0.3 µm) to the minor
dimensional, structural and chemical differences i n the grains and grain
boundaries which yield higher levels of light absorption and scattering, rather
than direct effect of grain size or sample thickness.
Casolco et al 2008 (85), assessing a way to produce translucent (50nm) sized
YTZP pointed out that the effect of grain size is not as clear as the scattering
mechanism of grain boundaries. They claimed that ― However, it is probable that

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15
when the crystal size (effective distance between grain boundaries) is
significantly smaller than the wavelength of visible light (400 –700 nm) they
should not interact significantly with light ‖.
Oxygen vacancies (with trapped electrons ) or color centers were referred to
in literature to have even more impact on increasing scattering, hindering forward
and in -line transm ittance and shift color to darker than that observed with
residual pores whereas grain boundaries effect was negligible (89). Moreover,
annealing in oxidizing atmosphere to remove color centers improved the
transmittance of light in spite of increasing por osity as proved by Zhang et al
2011 (89).
In summary manufacturing techniques; top – down approach / bottom -up
approach (87), besides sintering conditions; sintering method (whether plasma
spark, electric current and/or heating furnaces), heating rate, final temperature,
pressure application and controlling atmospheric conditions while sintering were
found to affect the resultant microstructure in terms of; density, porosity, grain
size, grain boundaries and color centers ( Oxygen vacancies) , and therefore affect
the optical properties of the material (86), (89) .
Type of dopant in the material is repo rted to have an impact on esthetic
outcome. A dopant is classically defined as an element incorporated in trace
amounts to alter the chemical properties . They are used mainly as stabilizers,
sintering aid, coloring aid, and for aging resistance. Dopants are present in
zirconia either as a distinct phase or as a solid solution (90).
The addition of alumina dopant was shown to deteriorate the transpa rency
although nanometric grains and high density have been achieved . The low
transparency was induced by the strong birefringent scattering, which is

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16
attributed to the distribution of alumina dopant along the grain boundaries of
zirconia as prove d by Zhang et al 2011 (83) and Fujisaki et al 2012(91).
Using cerium as a dopant deteriorates the esthetic outcome as well, CeO 2 is
yellow and products based on commercially available Ce -TZP powders range
from light yellow to almost brownish (92). A further com plication is due to the fact
that when Ce+4 is reduced to Ce+3, due to the high concentration of Oxygen
vacancies Ce -TZP tends to become dark gray. Since some food have reducing
capabilities ( e.g.: glucose and lactose) consequent darkening of such restorat ion
is expected (92).
2. Coloring Technique and Esthetic Outcome :
As previously said the color of raw Y -TZP is white (73), however it can be
easily colored through :
Pre-shaded Y -TZP:
In one technique, metal oxides are mixed with the starting Y -TZP powder
before sintering at high temperature, this technique has successfully led to the
reproduction of human teeth shades as mentioned by Cales B 1998 (93).
Manufacturers reported advantages for their p re-shaded zirconia product s such as
(94);
1. The pre-colored shading system produces a homogenous color in the
restoration with more predictable results.
2. Increases blending or chameleon effect and reduce the post sintering
modification needed.
3. More than one study pointed out that zirconia coloring liquids if used
instead of pre -shaded may affect mechanical outcome (95-99) Hjerppe et al 2008

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17
(95) reported that biaxial strength is dropped with coloring and the amount of
decrease is both shade and time dependent .
4. It eliminates the need for handlin g very acidic coloring liquids which can
affect the life of the furnace (94).
5. Saves time as n o drying is needed and less application time for shades and
stains (94).
However, Aboushelib et al 2010 (100) stated that pre -colored zirconia
frameworks did not offer any advantage of increased predictability over the
uncolored ones . Moreover Spyropoulou et al 2011 (76) mentioned that intense
shaded specimens significantly lower ed the translucency in terms of contrast ratio
than both light and medium shaded, w hich will decrease the esthetic outcome and
increase the need for extra cutting back, veneering and /or staining.
Much more predictability and minimizing characterization are targeted by
production of pre -shaded multilayered polychromatic zirconia blocks or blanks to
enhance going monolithic with maximum esthetic outcome . Yi Fu et al 2009 (101)
assessed 5 graded colored dental zirconia ceramics made by adding colorants and
their combinations into a 3Y -TZP powder , presented good mechanical
properties; The overall density of colored zirconia ceramics was over 99.7%, the
crystalline phase was tetragonal, bending strength was over 900 MPa which was
slightly lowered than that of the uncolored zirconia, fracture toughn ess was
slightly higher. Good chemical stability in acetic acid was observed even after
aging treatments, and was suitable for dental clinical use. While J Zhao et al
2013 (102)search ed the idea by processing a bi -colored zirconia and mentioned that
the co lor gradient zone in the bi-colored zirconia was a relative weak region
mainly due to the critical inhomogeneous micro structure, which probably related

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18
with granule packing defects and local enrichment of Fe2O3. And stated that
―there is still a large opportunity for further improvement of this technique ‖.
KATANA Zirconia ML full contour zirconia from Kurary offere d the
world‘s first polychrome zirconia in 2014 with integrated color shift ; starting
with a deeply chromatic cervical shade, 2 transitional shades, and ending with an
enamel shade (103).
Customized coloring with coloring liquids:
This technique involves the infiltration of machined restorations at the pre –
sintered stage that have been brought into a highly porous state with special
coloring solutions to produce work pieces of various shades (90), (104).
The solutions are preferably Water – or alcohol -based. Suitable salts or
complexes are preferably those from the group of the rare earths or the 2nd or 8th
subgroups, in particu lar Pr, Er, Fe, Co, Ni, Cu (104). iron (Fe) is used for brown
(main ingredient of A shaded coloring liquid ) (90) , erbium(Er) is used for light
violet, neodynium (Nd) is used for light pink, cerium (Ce) is used for cream
and/or orange, terbium (Tb) is used for light orange, manganese (Mn) is used for
black, and praseodymium (Pr) is used for dark yellow (105). Ions of these salts
appear in liquids as acetate, chloride, nitrates, nitrides as well as OXO
complexes. Stabilizing agents or complexing agents are u sed to stabilize the
metal salts in their oxidation stage and in solution , and finally grinding auxiliaries
as well as organic dye stuff pigments are there to facilitate matching of the color
(104).
These solutions can mainly be applied through:
 Immersion of the workpiece in solution for a defined time and
concentration.

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19
 Deposition of the solution by means of spraying process .
 Deposition of solutions by means of suitable application instruments
as; brush, swab …etc .
. After drying, at the initial stage of heating after immersion to porous pre –
sintered zirconia block, the anions (acetic, chloric, and nitric ions) probably
burned out or vaporized, and disappeared on the surface of the pores of the
zirconia block (104). The metal ions formed an oxide layer on the surface of the
pores of the zi rconia block . It can be assumed that these metal ions rarely reacted
with zirconia below the pre -sintering temperature (104). This means that these
metal oxides formed a new product with zirconia via a solid -solid reaction or
remained as oxides at the boundaries around zirconia grains in the final sin tering
stage (1350 -1600șC) (96).
The effect of different solutions, concentrations , time and method of
applications on the final esthetic outcome was not sufficiently studied in
literature. Suttor et al 2004 (104) reported that the depth of color is dependent on
the effect of concentration of coloring liquid rather than time of application . PH
value changes and the rele ase of ions were mentioned also as secondary factors
controlling depth of the color . Shah et al 2008 (90) tested concentrations of (1% –
5% and 10% wt ) of three different coloring liquids namely; Ceriu m acetate,
Cerium chloride and bismuth chloride on colo r reproduction . They stated that
Coloring with cerium or bismuth salts produced perceptible color differences
even at the lowest concentrations . Cerium based led to deeper cream color while
bismuth based led to deeper orange color. In all case scenarios si gnificant color
difference were found between colored and non colored control groups, while no
significant difference between 5% and 10% in terms of color production with
significant difference in case of 1% compared to any of other concentrations.

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20
Kim H -K and Kim S -H 2014 (106) assessed the application with brushing
technique that is recommended by some manufacturers to enhance controlling of
color distributio n and characterization, number of layers of coloring liquid
appli ed was the main variable tested t hrough increase from 1 to 5 layers. The
results showed that the increased number of colo ring liquid applications reduced
the lightness (darker samples) and opalescence of monolithic zirconia and made
it more yellowish (chromaticity) although its translucency couldn‘t be controlled
by the coloring procedure .
These techniques of infiltration with a coloring liquid although were
thought to had theoretically more customization and characterization few
drawbacks as inhomogenity and infil teration of the surface layers more than the
bulk material had been reported (107) as Shah et al 2008 (90)referred to this as a
result of increased coloring liquid concentrations , that a large amount of solvent
was evaporated with sintering, leading to an increased dopant concentration on
the top s urface of the discs. That would explain the deeper chroma observed on
the same surface compared to the bottom surface. Other authors (108) , (109) related
this phenomenon to Oxygen vacancies and diffusivity of Oxygen in interfaces or
grain boundaries .
3. Surface Finish and Esthetic Out come :
The estheti c quality of the restoration depend s to a great extent on surface
texture . As The color and glossiness of an object depends on its surface spectral
reflectance. The reflectance of a surface is a sensi tive function of its
microtopography as very well proved by Bennett and Porteus 1961 (110). A
smooth surface reflects a greater amount of light than does a rough surface, and a
rough or irregularly textured surface will reflect an irregular and diffuse pattern
of light, which will change the color of the restoration (111).

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21
Furthermore, finishing and polishing procedures may influence the color of
the porcelain . Rough porcelain surfaces are more susceptible to staining than are
smooth porcelain surfaces (112) , (113) . Thus, texture is important for the color of the
restoration (112) , (114)..Therefore the optical properties of the full contour zirconia
as a monolithic restoration with no veneer may be i nfluenced by the su rface
finish that had been debatable in literature considering wear of zirconia
antagonist especially when it comes to full contour zirconia .
While a misconception was referring the cause of antagonist wear to the
hardness of zirconia material therefore supported a final layer of glaze with lower
hardness, Recent studies on wear of antagonist enamel demonstrated mostly that
adequate surface finish of zirconia restorations resulted in the least wear of
antagonist enamel among various dental materials (61). These results confirmed
that the antagonist enamel wear is significantly affected by the degree of surface
finish occurring during res torative procedures of grinding and polishing as was
early proved (115). According to Lim et al 2008 (116)., testing many ceramic
materials the surface roughness was totally independent of the hardness, but
strongly depended on the crystal grain size , content, d istribution, and
composition . Therefore, it is concluded by Ban S et al 2013 (117) that zirconia can
be polished to a smooth surface due to the homogeneous and fine microstructure .
Hmaidouch et al 2014 (118)interestingly found that zirconia surface roughness is
much lower than that of conventional veneering ceramic apart of kind of suface
treatment .
While literature compared the polished and glazed zirconia surface s by
means of profilometer (119), laser specular reflectance (120), scanning electron
microsco py (SEM) (121), atomic force microscopy (AFM) (122) and visual
assessment (123), it mostly related its effect on mechanical output presented mainly
by wear of ceramic and antagonist rather than esthetic outcome . Although a

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22
number of studies related surface finish of conventional porcelains to the esthetic
output (111-113), (124) a single study (125) to our knowledge was identified that
investigated the effects of polishing and glazing methods on the color of zirconia
restoration especially for full contour zirconia restorations .
Glazing :
is not only an option for aesthetic improvement but may also be required for
some favorable fitting wear after insertion. A glazed ceramic surface is generally
considered beneficial because it may increase the fracture resistance and reduce
the potential abr asiveness of the ceramic surface by sealing the open pores of the
fired porcelain surface (113) , (126). Verina Preis et al 2012 (126) explained that t he
glaze over zirconia samples may have filled the rough zirconia surface and deep
glaze layers might hav e been protected by sticking zirconia causing the glazed
zirconia to record high fracture resistance values. Sealing the pores moreover was
thought to enhance color stability and p revent staining as evident by Caner
Yılmaz et al 2008 (112) who found no staining with glazed specimens opposed by
stained patches for ground and repolished previously glazed samples.
Older studies of predecessor ceramics before full zirconia spread showed
much more support for glazing to have an ideally smooth sur face and many
Investigators have emphasized that polishing techniques were unable to provide
surfaces which are as smooth as glaze (124) , (127) , (128). Patterson et al 1991 (129)
compared the effect of glaze and polishing kits, including diamond paste, on
surface texture and reported that the lowest surface roughness was obtained by
glazing rather than polishing. Fuzzi et al 1996 (128) demonstrated by SEM analysis
that glazed surfaces were superior to all other polished surfaces. The findings of
Motro et al 2012 (124) study indicate d that glazing and reglazing procedures
resulted in a smoother surface texture than either polishing techniques or
diamond rotary cutting instrument abrasion.

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23
However, effects of the glazing on zirconia are uncertain whether this
coating is effective in improving surface quality. Beuer F et al 2012 (1)
mentioned that glazed full contour zirconia increased the antagonist wear
significantly and moreover decreased the light transmission of full conto ured
zirconia. While the authors related increased wear to more surface roughness of
glazed surface, the decreased light transmission was explained by the glaze layer
representing a second interface for light to pass through that definitely cause d
more scattering and less transmission. Verina Preis et al 2014 (130) confirmed
this when testing surface roughness of monolithic zirconia after dental adjustment
treatments with in vitro wear simulation to conclude that glaze increase
roughness considerably even from as sintered samples. As a pr oof many studies
also reported smooth zirconia surfaces cause d less wear of antago -nistic enamel
than conventional veneering ceramics. (118) , (131-133)
Moreover, the routine chairside adjustments of occlusal contacts, pr oximal
contacts or contour modifications can easily remove the thin glaze layer leaving
the zirconia surface directly exposed to wear processes and environmental
influences of the oral cavity , or even glaze layer was known to be worn within
the first six mo nths after insertion of the restorations (134),. Afterwards extra oral
reglazing is not the best option as it multiply patient visits and moisture trapped
in the ceramic res toration should be considered, leaving the first option to
smoothen the surface by intra-oral polishing. Other studies supported polishing
surface before glaze application in order to attain smooth surface under glaze
even it got worn after time of service (135).
Polished ceramic surfaces have been reported to be equal or surpass the
smoothness accomplished with surface glazing (136). Several reports have
described different polishing techniques for ceramic restorations and supported
the use of polishin g as an alternative for glazing (114), (127) , (137). A mirror polished

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24
zirconia surf ace is under taken in the dental laboratory or in the oral cavity for
occlusal adjustment. Grinding, polishing rotary systems and polishing pastes are
available in the market for mirror -finish zirconia surface (61).
Grinding :
The hardness of zirconia is hi gh (HV 1,160 –1,300), but lower than alumina
(HV 1,800 –2,200) and diamond (HV 10,200). Therefore, zirconia can be easily
processed by the instruments coated with diamond abrasive grains fixed with
metal, glass, and artificial rubber to a stainless steel sha ft (61). It has been
confirmed that larger diamond grains show higher grindability for zirconia (138) .
However, the surface roughness is also higher as coarse grinding increased the
surface roughness values creating grooved zirconia surfaces evidenced by
Hmaidouch et al 2014 (118) who reported that surface roughness of coarse ground
zirconia surface reached 12.57 ±4.40µm. these results were supported with results
of Curtis et al 2006 (139) of wet and dry grinding and Kou W et al 2006
(140)studied of amount of roughness by grinding .
Meanwhile the multi – step grinding with finer particles resulted in smoother
surface comparable to the glazed or even equaled that of first step of coarse
polishing (61). An interest finding by Hmaidouch et al 2014 (118) that no
significant difference was found between the surface roughness of fine -ground
FZ specimens and the roughness of glazed FZ, which was explained by the very
small bubbles within the glaze layer .
Therefore, the grinding rotary instrument should be changed sequentially
from a large (100-300 µm)to medium (30 -60 µm) and finally small grain size (3-6
µm) of the diamond abrasives . Consequently, this manner resulted in a fast and
homogeneous smooth surface , and enabled a fast move to the next step, i.e .
polishing (141).

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Polishing :
Diamond grains fixed with artificial rubber of different coarseness for
intraoral or extra – oral use are available as polishing kits for zirconia . Coarse
polished surfaces were equal in roughness to the fine ground ones, although
medium and fine polishing was reported to significantly reduce roughness to
minimum , it was evident by Ban S et al 2013 (117) that minimum roughness was
strongly correlated to size of diamond grains and crystal grain size; 3 types of
slightly diff erent grain sized zirconia (0.3 -0.4 and 0.5 µm) among 4 other types of
dental ceramics of larger grain sized were finished with three subsequently
smaller diamond rotary instruments and two diamond pastes, the three zirconia
products were the least surface roughness following each polishing step.
Roughness was reduced with each single step and the smallest grain sized
zirconia was the lowest surface roughness (about 0.1 µm). The authors concluded
that surface roughness was independent to the hardness but str ongly depended on
the crystal grain size and diamond size .
While Hmaidoch et al 2014 (118) reported a roughness value of 2.41 µm for
fine polish ed monolithic zirconia samples and considered this value a low surface
roughness , Verina Preis et al 2014 (130) reported polished zirconia surfaces with
0.2 µm for both tested zirconia materials , they mentioned this value to be similar
or even less than that reported for glaze layers. (131) , (142) . The authors accordingly
recommended the use of a zirconia polishing kit as a reasonable and time -saving
alternative method to re -glazing. They stated that ― Nevertheless, even longer
polishing times may be necessary to completely remove deep grinding grooves.
Thus, hard zirconia surfaces need to be polished accurately with out omitting any
of the polishing steps ‖. Traini et al 2014 (143) found that fine polishing rather
than coarse polishing and milling treatment showed a significant decrease in

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26
roughness and surface complexity while it hindered fracture toughness with a
significant microcrack increase and surface embrittlement . The effect of
polishing in triggering stresses inside zirconia structure and decreasing aging
resistance was an issue of discussion and a factor to be considered with all –
zirconia restorations.
Superior mirror finishing and further smooth surface is thought to be
acquired through polishing pastes. Polishing pastes for zirconia mainly contain
diamond grains (1 -6 µ) and fine other oxides (less than 0.5 µm) such as anatase
(TiO 2), corundum (Al2O3), zinc oxide (ZnO), and Pumice (SiO2) (141). These
diamond pastes are usuall y used to polish with plastic, rubber cone and /or
brush es. T Meyazaki et al 2013 (61) reported further smoothness for polished
zirconia surfaces with polishing pastes application independent of zirconia type
or polishing paste type, while the use of mechanical tooth cleaning pastes showed
no change in surface.
Glossiness of zirconia becomes even more important concerning full-
contour restorations because besides determining whether the final polishing is
enough or not it enhances the esthetic outcome and life -like appearance (61). T
Meyazaki et al 2013 (61) reported increased glossiness with decrease of diamond
grain size and increase in grinding and polishing st eps, steep glossiness increase
was found when surface roughness is lower than 0.3 µm.
Reviewing literature concerning zirconia surface roughness that is expressed
in many times as the amount of antagonist wear showed t hat two phases were
consecutive. The first phase accompanied the beginning of zirconia spread to the
dental field mainly in the early 2000s. Tambra et al in 2003 (144) reported that
zirconia caused greater enamel wear than did the IV gold control, although the
polished zirconia caused le ss wear to the enamel abrader than the processed

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27
zirconia. They described that the surface was mirror -polished with diamond
paste. However, the polishing method and the smoothness of zirconia were not
discussed . Culver et al.2008 (145) reported that zircon ia (Cercon and Lava) caused
more enamel loss than composite resins (MZ100 and Z100) and leucite –
containing glass (Empress). Shar et al.2010 (146) reported that the polished
zirconia showed larger enamel loss than the glazed one.
The polishing conditions of these reports were unclear. In the 2010s, various
polishing materials and instruments for zirconia have been introduced and the
conclusion began to change as zirconia entered its mature phase , with the
development of peripheral technology.
In 2010, Jung e t al (135) They reported that the enamel loss on the mirror –
polished zirconia was significantly less than those of glazed and porcelain –
veneered ones. On the other hand, Albashaireh et al. 2010 (147) demonstrated that
the degree of antagonistic tooth wear was less in zirconia than feldspathic dental
porcelain s, representing that the zirconia may be more beneficial in terms of
antagonistic tooth wear .
In 2011, Sorensen et al (148) reported that the polished Lava showed small
enamel loss similar to that of gold alloy (Aquarius). At the same meeting of
IADR , Basunbul et al . (149) demonstrated that polished Wieland zirconia caused
significantly less wear to enamel than the glazed Wieland zirconia, Ceramco
porcelain, and Cerec Mark II. They concluded that the polished zirconia remained
unchanged, but the glazed zirconia showed significant loss of the glazed layer.
Yang et al . (150) measured the enamel wear against Zirkonzahn Y -TZP (polished,
stained, stained then glazed), Acura Y -TZP, Wieland Y -TZP, a feldspath ic
porcelain. They demonstrated that the antagonist wear of the three Y -TZP
products was significantly less than veneering porcelain because the surface
character of Y -TZP is relatively homogeneous, and Zirkonzahn with staining and

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28
glazing was significantl y more abrasive than the other Y -TZPs without glazing.
Preis et al (131) reported that antagonist wear against zirconia was lower than the
wear against porcelain . Kuretzky et al. (151) measured the enamel loss against four
kinds of surface -treated zirconia (rough, polished, glazed, and veneered Lava)
and e.max CAD using. They demonstrated that the polished zirconia showed the
least wear after abrading with a steatite sphere.
In 2013, Janyavula et al (152) compa red polished, glazed and polished then
reglazed . They concluded that highly polished zirconia is more desirable than
glazed zirconia and more wear friendly . Furthermore, Stawarczyk et al (153)
reported that the polished zirconia showed a lower wear rate on enamel
antagonists as well as within the material itself . Kontos et al (154) concluded that
the polished zirconia seems to have the lowest wear on the antagonist, in contrast
to the other types of surface treatment (sandblasted, ground, and glazed) . Sabra h
AHA(155) suggested that polishing the zirconia surface might be the best treatment to
reduce surface rou ghness and antagonist wear of synthetic hydroxyapetite and bovine
enamel. ,
In 2014, Hmaidouch et al (118) concluded that grinding the glazed FZ using a
special three -step system could deliver smooth surface comparable to those
untreated glazed FZ , and polishing achieved even smoother , fewer defects
surfaces. Verina Preis et al (130) assessed the surface prop erties of FZ after
sintering, grinding and polishing steps and stated that ― In clinical application,
zirconia should be polished according to the instructions of the manufacturer to
keep values for surface roughness and phase transformation as low as possi ble‖.
4. Aging and Esthetic Outcome:
Lughi and Sergo 2010 (156) in a critical review defined Low temperature
degradation ( LTD ) or aging as the spontaneous t–m transformation occurring

Review of Literature
29
over time at low temperatures, when the t–m transformation is not triggered by
the local stress produced at the tip of an advancing crack. It is clear that, once
already transformed to the m-polymorph, zirconia cannot exhibit phase
transformation toughening ( PTT), just like a used match cannot be lit again.
Overall PT T and LTD are based upon the same phenomenon, the t–m
transformation of zirconia, and, to date, we cannot exploit the remarkable
possibility of the former without exposing ourselves to the risks of the latter.
Reported drawbacks of the LTD t–m transformation were ; enhanced wear
rates (157) with release of small zirconia grains in the surrounding environment,
roughening of the surface finish and surface uplifts with both mechanical (158) and
aesthetic worsening (159).
Although hundreds of laboratory researches dealt with the effect of aging
and its theoretically assumed mechanisms on the mechanical outcome and
serviceability of the material (156), no studies to our knowledge have discussed the
esthetic and color changes upon such phenomenon, however through studying the
factors controlling LTD and its effects on the material microstructure and surface
, esthetic outcome and stability of the material with its variable products and
processing techniques may to a great exte nt be affected.
T-m transformation is governed mainly through three main axes ; the
chemical metastable nature of the tetragonal phase (related to the stabilizer used) ,
the stresses applied or residual and the grain size GS . These axes were actually
interli nked and affect ed one another in a complex way (156). For example, an
increase in the content of stabilizer induce s a reduction of the grain size (160),
while a larger grain size leads to higher local stress (161).
Reviewing literature showed that a s the type and concentr ation of the used
dopant differed , the stabilizing mechanism and the degradation mechanism

Review of Literature
30
differ ed as well (156), with no trials to assess this effect on optical properties. Y 2O3
is the most widely used stabilizer in high -tech application of zirconia; because of
charge balance reasons, the introduction of Y2O3 in the ZrO2 lattice g ave origin
to Oxygen vacancies which were one of the mechanisms proposed for the
stabilization effect (162). At the same time these Oxygen vacancies was thought to
be the color centers for the material (108), when the coloring salts were added the
anions were lost with sintering leaving the cations in the lattice of Y -TZP, which
ultimately conferred coloration to the part (104).
Concentration of the dopant, the temperature, water presence, time o f
immersion, initial mon oclinic content and grain size were reported to affect the
transformation to monoclinic phase (156). To date, there is no accepted mechanism
to explain the phenomen on, but only informed speculations. The soundest were
the following;
– Lange et al 1986 (163) propose, based on some TEM observations, that
water reacts with Y 2O3 to form clusters rich in Y(OH)3; this leads to a depletion
of the stabilizer in the surroundi ng zirconia grains which are then free to
transform to monoclinic.
– Yoshimura et al 1987 (164), water vapor attacks the Zr–O bond, breaking it
and leading to a stress accumulation due to movement of –OH; this in turn
generates lattice defects acting as nucleating agents for the subsequent t–m
transformation.
– Chev alier et al 2009 (165) propose d that O-2 originating from the
dissociation of water, and not OH −, is responsible for the filling of Oxygen
vacancies which is believed to be on e of the causes of destabilization and, hence,
of LTD and for the long diffusional path.

Review of Literature
31
Irrespective of the mechanism, it is well established that the t–m
transformation:
(i) Starts from the surface of the sample and then proceeds inward in a so –
called ‗‗nucleation -and-growth ‘‘ process ,
(ii) It causes surface uplift s, through grains pull -out and microcracks with
ensuing aesthetic degradation,
(iii) It open the possibility for water to penetrate below the surface, thus
propagating the t–m transformation to the interior of the sample , and finally,
(iv) It leads to the development of major cracks (166).
It is in response to these problems affecting Y-TZP, that ceria, CeO 2 has
attracted a lot of interest as stabilizer. Very interesting finding that Ce -TZP
samples were basically unaffected by the aging cycles in water vapor (167) and
even studies more focused on the dental applications of Ce-TZP confirm ed this
finding . A typical Ce -TZP composition, capable of t–m transfor mation, contains
8mol% of ceria. Above 12mol% the system is non-transformable. Ce -TZP with
12 and 14mol% showed negligible degradation even after 500h at 150◦C in water
vapor; after 360h in water at 80◦C (167). Ce-TZP with 8mol% ceria showed less
than 10% monoclinic on the surface (168).
Chemically, Ce -TZP present ed the problem that Ce+4 can be relatively easily
reduced to Ce+3, which does not have the same stabilizing ability toward t-
zirconia (92). Even sintering in air can lead to a reduction, and ther e is evidence
that the chemical reduction can be triggered also at room temperature by the
stress locally generated by the t–m transformation . As mentioned before, from an
aesthetic point of view, Ce -TZP poses more problems than Y -TZP to the dentists:
CeO 2 is yellow and products based on commercially available Ce -TZP powders

Review of Literature
32
range from light yellow to almost brownish. A further complication is due to the
fact that when Ce +4 is reduced to Ce +3, due to the high concentration of Oxygen
vacancies Ce -TZP tends to became dark grey (92). Since some foods have
reducing capabilities (glucose and lactose, for example), the possibility cannot be
excluded that, on the long range, Ce+4 could be reduced in the oral cavity with
consequent darkening of the zirco nia-based part .
Sergo V et al (92) recorded their observation about deformation bands on the
tensile side of Alumina/ceria stabilized bars upon four point bending test, that
represented localized tetragonal to monoclinic transformation, these bands
became increasingly darker. XPS revealed that these darker bands were
characterized by a high concentration of Ce+3 as opposed to the undeformed
bands with Ce+4 was the predominate oxidation state. It was suggested that these
stresses facilit ate the reduction of cerium with gradient in stress motivating the
diffusion of Oxygen vacancies .
Coloring procedures and surface finishing for monolithic zirconia restoration
that‘s in direct contact with oral fluids may have its effect also in enhancing
thermodynamic kinetics in a way to encourage t -m transformation through
affecting chemical metastability by nature of coloring liquid, induce stresses
while treating the surface and changing microstructure in a way or another (156) ,
(158). Shah et al (90) reported that Coloring 3Y -TZP with either cerium or bismuth
solutions up to 10 wt % did not affect the resistance to low temperature aging,
which was excellent for both unshaded controls and colored groups with no
detectable amount of monoclinic zirconia a fter aging in autoclave for 10 h . Fu Yi
et al (169) meanwhile stated that the nucleation and growth of monoclinic phase
were detected by AFM in surface of both colored and uncolored zirconia after
accelerated aging in autoclave in steam at 134°C, 2bar, for 4hs. Numerous studies
have investigated the effects of surface treatments on phase transformation in 3Y –

Review of Literature
33
TZP (170-172) . As zirconia restorations are exposed to a humid environment and
cyclic loading in the oral environment, the evaluation of the additive effects of
surface treatments on the LTD of zirconia ceramics is essential for the successful
application of zirconia ceramics in dentistry.
M-phase generated by aging or surface treatments was thought to be able to
recover by heat treatments at sufficient ly high temperature (173). Several authors
reported that heat treatments in the temperature range of 900 -1200 °C can induce
reverse phase transformation from the m -phase to t -phase after aging, grinding or
sandblasting of Y -TZP. (166) , (173) Denry et al 2010 (174) reported that reverse phase
transformation in 3Y -TZP was initiated at temperatures as low as 350 °C and
completed at 550 °C.
Regarding grain size (GS) effect on LTD, literaure reported that reducing the
average GS in zirconia -based ceramics has a beneficial effect on the stability of
the tetragonal phase and therefore on LTD. Lughi and Sergo 2010 (156) stated that
practically, the lower the temperature, the smaller is the critical size. A reduction
of grain size below a certain critical value has the potential of fully inhibiting
LTD. Although the vast majority of the available data refer to measurements
conducted above 100◦C- a number of reports suggest that at room temperature for
pure zirconia powder s the critical size is in the range of 5 –10nm (175)- similar
values could be calculated following a general framework proposed by Mayo and
co-workers and well tested f or temperatures above 300◦C (176) .
Lughi and Sergo ’s (156) approach enable d the calculation of the critical size
for Y -TZP powders, which was about 90nm for 1.5Y -TZP. While proposed that
the grain size of 3Y-TZP ceramics should be less than 0.3 µm for dental
applications . Tae-Hoon Lee et al 2012 (158) reported that the stability of the t-

Review of Literature
34
phase is retained after autoclaving with fine grain size (smaller than 0.5 µm)
zirconia types with only a slight amount of m -phase was seen. In contrast, the t –
phases in the two other groups with large grain size (larg er than 0.7 µm) were
destabilized and transformed to m -phases.
Tests for LTD of the zirconia ceramics are usually performed in autoclave or
steam chambers, where the pressure of the water vapor, temperature, and elapsed
time are controlled experimental variables (156).
The complex interaction between the monolithic zirconia material , coloring
procedure ,method of surface smoothening and the LTD behavior after exposing
to oral environment on the esthetic outcome of an all -zirconia restoration rather
than its mechanical outcome had not been efficiently searched in literature, and in
the same time is of great interest in the development phases of such restorations.

Aim Of The Study

33
Aim of the study:
This study was held to assess:
 Color reproduction
 Translucency
 Opalescence
Of full -contour zirconia restorations with varying:
 Coloring techniques:
 Monochromatic dyeing ( dipping).
 Custom dyeing.(brushing)
 External surface treatments:
 Polishing
 Glazing
 Polishing and glazing.
Before and after aging .

Materials &
Methods

33
Materials:
InCoris TZI blocks*:
Nanostructured Yettrium stabilized tetragonal zirconia polycrystals. (Fig.1)
Figure 1: InCoris TZI block

Table 2: Standard composition of inCoris TZI.
Standard
Composition (In wt %)
ZrO2+HfO2+Y2O3 ≥ 99.9%
Y2O3 5.4%
HfO2 ≤ 5%
Al2O3 ≤ 0.005%
Fe2O3 ≤ 0.02%
Other oxides ≤ 0.2%

* Sirona Dental Systems GmbH , Bensheim, Germany.

Materials and Methods
37
InCoris TZI Coloring Liquid*:
Aqueous coloring liquid for shading of z irconia restorations of shade A2.
(Fig.2)

Figure 2: inCori s TZI coloring liquid
VITA AKZENT Glaze†:
A low-fusing glass -ceramic . (Fig 3)

* Sirona Dental Systems GmbH , Bensheim, Germany .
† VITA , Zahnfabrik H. Rauter GmbH & Co. KG.

Figure 3: VITA Akzent glaze and fluid

Materials and Methods
38
Zi-Polish*:
Zirconia polishing paste .(Fig.1)

* bredent GmbH & Co.KG
Figure 4: Zi-Polish zirconia polishing paste.

Materials and Methods
39
I) Grouping of the Samples : (Table 3)
A number of sixty monolithic zirconia ( MZ) plates were machine cut and
then divided into two main groups according to the coloring technique as following:
• GP I : (n=30) monochromatic dyeing; thirty (MZ) plates were colored
by dipping in inCoris TZI Coloring Liquid * according to manufacturer instructions.
• GP II : (n=30) custom dyeing; the other thirty MZ plates were
colored with the same coloring liquid applied to the surface by a brush in a
customized manner according to manufacturer instructions.

After sintering of all M Z plates, each group was subdivided into three
subgroups according to surface treatments as following:
• Subgp (G): (n=10) in which external surfaces were g lazed only.
• Subgp (P): (n=10)in which external surfaces were polished only.
• Subgp (PG): (n=10) in which external surfaces were polished then
glazed.
Table 3: Samples Grouping .
GP
Sub GPI dipping GPII brushing Total
Subgp (G) IG (n=10) IIG (n=10) 20
Subgp (P) IP (n=10) IIP (n=10) 20
Subgp (PG) IPG (n=10) IIPG (n=10) 20
Total 30 30 60

* Sirona Dental Systems GmbH , Bensheim, Germany .

Materials and Methods
40
II) Samples Preparation :
inCoris TZI 40/19 blocks* with the dimensions (40 ×19×15 mm) were
machine cut with a digital microtome slicer (Micracut 150 )† Low Speed
Precision Cut Off Machine (Fig.5) . with variable arbor speed 0 -1000 rpm.

Dimos 19 -130†, 127 mm diameter disc with fine/low concentration of 150
mesh size metal -bonded diamond abrasives to a depth of 40 mm was used for
cutting . It was specified for use with hard/brittle materials, s tructural ceramics,
electronic substrates, alumina, zirconia and silicon carbide.

* Sirona Dental Systems GmbH , Bensheim, Germany .
† metkon metallography,Kemet International Ltd. Turkey.
Figure 5: Micracut 150 percision cutter.

Materials and Methods
41
The metric micrometer was set at 1.25 mm (Fig.6) , while the speed adjuster
was set at 2 representing a l ow speed of 200 rpm due to the partial sintering state
of the zirconia material (Fig.7) .

Figure 6: the built -in digital micrometer.
Figure 7: Speed adjuster.

Materials and Methods
42
The cut samples were sixty rectangular -shaped (MZ) plates with 1.25 mm
thickness and (19×15 mm) for width and length (Fig.8 ). The thickness was
verified with a digital micrometric caliper* with the accuracy of 1 µm on five
different sites (center and each corner of specimen) of each specimen (Fig.9 ).

* 8‖ vernier caliper (Mitutoyo, Tokyo, Japan )
19 mm 15mm
Figure 8: Monolithic zirconia plate.
Figure 9: Verified thickness with digital micrometer.

Materials and Methods
43
Coloring the samples :
Before dyeing all samples were cleaned with water and a soft tooth brush
and left to dry for a minimum of 30 minutes .
Monochromatic dyeing (dipping technique):
Thirty samples were selected to be submerged in a special coloring jar
(inCoris TZI dip tan k*) containing amount of the coloring liquid ( inCoris TZI
coloring liquid A2 *) that ensured samples were totally submerged and left for 5
minutes according to manufacturer instructions (Fig. 10). After which s amples
were removed using a pair of plastic tweezers and hanged for 30 seconds in a
vertical position to allow dropping of excess liquid traces before being placed on
a non -absorbable paper .

* Sirona Dental Systems GmbH , Bensheim, Germany .
Figure 01: inCoris TZI Coloring Liquid A2 and
Dip tank

Materials and Methods
44
Customized deying (brushing technique):
Applied to the other thirty remaining samples. The surfaces of each sample
that will not be colored were identified with a small notch in one corner. A size 8
brush was used to apply the coloring liquid (inCoris TZI coloring liquid A2*) to the
intended surface of each plate in one direction for 5 brush strokes with no drying
time between applications according to manufacturer instructions (Fig. 11).
.
After dyeing a ll samples were dried under an infrared drying lamp† for 30
minutes before sintering.

* Sirona Dental Systems GmbH , Bensheim, Germany .
† ZIRKONLAMPE 250, Zirkonzahn, GmbH Figure 11: inCoris TZI coloring liquid brushed to the surface

Materials and Methods
45
Sintering:
The sintering process was performed in Sirona inFire HTC speed furnace
(SDS)* (Fig.1 2).

The samples were placed on sintering boats specially designed for this
process , that were filled with the sintering beads, at least 1 cm apart from each
other (Fig.1 3).

* Sirona Dental Systems GmbH , Bensheim, Germany.
Figure 12: Sirona inFire HTC speed furnace
Figure 13: Sintering boat showing zirconia discs on
sintering beads.

Materials and Methods
46
The "Super Speed" program permanently installed in the furnace was chosen
for speed sintering. The duration of the program run was 90 minutes and sintering
temperature was 1540șC .
After the sintering process, the samples were left to cool down to room
temperature before further processing. Shrinkage about 20% (Fig.1 4) from original
dimensions was expected .
The final thickness is 1mm ±0.05 verified with digital micrometer *(Fig.15).

* 8‖ vernier caliper (Mitutoyo, Tokyo, Japan)
Figure 14: Shrinkage of zirconia disc after sintering
Figure 15:Verification of thickness after sintering.

Materials and Methods
47
Enviromental Scanning Electron Microscopy :
One random representative sintered sample from each colored group was
scanned under Enviromental Scanning Electron Microscope (ESEM)* (Fig.16)
for surface assessment before surface finishing procedures, with magnification of
500X .

* Inspect S, FEI company, USA .
Figure 06: Enviromental Scanning Electron
Microscope (ESEM).

Materials and Methods
48
Surface Finishing:
Ten samples of each different colored group were randomly chosen to apply
the specific surface finishing on each:
 Glazing:
VITA A KZENT glaze* powder was picked up with the tip of a modeling
knife, mixed with 1 – 2 drops of VITA Akzent fluid * to a thick consistency, a thin
layer of the mix was spread evenly on the entire specimens ‘ surfaces in only o ne
direction and for one brush stroke (Fig 17). The procedure was performed by the
same operator to minimize error then fired according to the firing chart in (Table 4)
in a conventional ceramic furnace Programat P 300 furnace† (Fig.1 8)

* VITA , Zahnfabrik H. Rauter GmbH & Co. KG.
† Ivoclar Vivadent , Schaan, FL.
Figure 17:Glaze is brushed on the sample's
surface

Materials and Methods
49
Table 4: Firing chart of VITA AKZENT glaze
VITA
AKZENT B
°C/
°F S
min t
°C/°F /min T
°C/
°F H
min L
°C/
°F
Glaze Firing 400/
757 4:00 80/108 790/
1337 1:00 450/
842
B:pre-drying temp , S: pre-drying time , t: heating rate , T: firing temperature, H:
holding time , , L: long-term cooling.

Figure 18: Glazed samples inside the firing furnace

Materials and Methods
50
 Polishing:
A Polishing kit (K0262 Dialite ZR Intra -Oral Adjustment finishing and
polishing syste m * ) (Fig.1 9) and polishing paste (ZI-Polish†) (Fig. 20) were used in
the following sequence :

*Brasseler (Br)USA.
† bredent, GmbH & Co.KG .
Figure 09:K0262 Dialite ZR Intra -Oral a djustment
finishing and polishing system
Figure 01: Zi-Polish paste with Wheel
Brush Rodeo

Materials and Methods
51
i Green course grinder (LD11CZR) (Fig.21) ,

ii Green medium polishing points for pre -polishing (W 16 -17-18 MZR
MED) (Fig.22) ,

Figure 21: Green course grinder (LD11CZR).
Figure 22: Green medium polishing points for pre –
polishing (W 16 -17-18 MZR MED) .

Materials and Methods
52
iii Orange fine polishing points for high luster (W 16 -17-18 FZR FINE)
(Fig. 23),

iv (ZI-Polish* ) diamond polishing paste ( with two different diamond
grain sizes , Nr. 36010025 ,) was applied with a special brush (Wheel Brush
Rodeo *) that is double loaded with natural horse hair for best results of
finalizing the surfaces (Fig. 24).

* bredent, GmbH & Co.KG .
Figure 02: Zi-polish diamond polishing paste applied with wheel brush Rodeo. Figure 23: Orange fine polishing points for
high luster (W 16 -17-18 FZR FINE) .

Materials and Methods
53
Polishing was carried out by low speed hand piece and an electric motor with
a rate of 7000 -1000 0 rpm under constant water coolant . Specimens were polished in
one direction, the bur was applied allowing its working surface to cover the
maximum surface area possible of the sample equal to that of the working part, then
held for 5 seconds before moving to the subsequent neighboring part. Thus
completing the whole sample surface in 60 seconds per bur. all 4 steps of polishing
was held with a total time of 4 minutes per sample . All specimens were polished by
the same operator while attem pted to apply constant pressure. The surface quality
was evaluated by two investigators to be clinically acceptable .

 Polishing and Glazing:
The remaining thirty samples were treated as a combination of the two
previously explained surface treatments repeating the following steps:
i Green course grinder (LD11CZR) .
ii Green medium polishing points for pre -polishing (W 16 -17-18 MZR
MED) .
iii Orange fine polishing points for high luster (W 16 -17-18 FZR
FINE) .
iv The glaze layer of ( VITA AKZENT Glaze*) was applied as
previously explained.
Thus all samples were ultrasonically† cleaned in isopropanol for 5 minutes to
be free of grease, then left to dry to be ready for the first phase of measurements .

* VITA , Zahnfabrik H. Rauter GmbH & Co. KG.
† Ultrasound Vita -Sonic II, Vita Zahnfabrik, Germany.

Materials and Methods
54
III) Measurements:
 Color Reproduction :
Color reproduction was measured using VITA Easyshade Compac t*
spectrophotometer (Fig.2 5). The VITA Easyshade Compact * was set to the
―Restoration mode ― and shade A2 was selected. The spectrophotometer aperture
was centralized on the center of each sample over a grey background (Fig.2 6)
with maximum intimate contact between the aperture and the flat specimen
surface. The button is pressed to measure the diffe rence in color ( ΔE) between
the specimen and the selected shade (Fig.2 7). The device was calibrated in the
calibration slot before each measurement for maximum standardization. Three
measurements were taken for each specimen and their average was recorded.

* VITA , Zahnfabrik H. Rauter GmbH & Co. KG.
Figure 05: VITA Easyshade Compact

Materials and Methods
55

Figure 06: The tip of VITA Easyshade Compact over
the sample during measurement.
Figure 07: Vita Easyshade Compact showed ΔE from the selected
shade A2

Materials and Methods
56
 Translucency and Opalescence :
A double -beam spectrophotometer (Cary 5000 UV –vis–NIR Spec –
trophotometer*,) (Fig. 28,29 ) using an integrating sphere attachment of 150 mm
diameter made with sintered poly-tetra-fluoroethylene (PTFE ) was used . The
specular reflectance component was excluded (SCE mode). Relative reflectance
data was recorded in the visible range from 380 to 780 nm at 5 nm intervals.
Measurements were recorded in Commission Internationale de l‘Eclairage(CIE)
1976 L*a*b* color spac e (CIELAB) relative to the stan dard illuminant D65 and
10◦ supplementary standard observer in the reflectance mode over a white
background (CIE L* = 99.9701, a* = −0.0711 and b* = 0.0499) and a black
back ground (CIE L* = 4.7487, a* = −1.6749 and b* = −1.5844), and in the
transmittance mode . The white standard was poly -tetra-fluoroethylene (PTFE)
plate (SRS -99-020, Spectralon®ReflectanceStandards† ) and the black
backgr ound was a black tile (CM -A101B‡.).
Color coordinates, CIE L*, a* and b*, were determined from the
transmittance and reflect ance data using a computer soft ware ( Cary WinUV
Software *). Each value was measured on five different areas of each specimen
including the center of specimen by moving it 1mm toward each quadrant
direction. Average L*, a* and b*values were used to calculat e needed
parameters.
The translucency parameter (TP) was o btained by calculat ing the color
difference of the specimen over the black and white backgrounds with the
following equation
TP = [(L∗B− L∗W)2+ (a∗B− a∗W)2+ (b∗B− b∗W)2]1/2

* Agilent Technologies Inc., Santa Clara, CA,USA
† Labsphere Inc., North Sutton, NH, USA
‡ Konica MinoltaOptics Inc., Tokyo, Japan

Materials and Methods
57
Where subscript B refers to the color coordinates over a black background
and the subscript W refers to those over a white background.
The opalescence parameter (OP) was calculated as the dif ference in yellow –
blue and red -green coordinates between the transmitted and reflected co lors using
the following equation:
.OP = [(CIE a ∗T− CIE a∗R)2+ (CIE b∗T− CIE b∗R)2]1/2
Where subscript T refers to the transmitted color and subscript R refers to the
reflected color over a black background.

Figure 08:Cary 5000 UV–vis–NIR Spectrophotometer.

Materials and Methods
58

Figure 09: Sample inside spectrophotometer

Materials and Methods
59
 Scanning Electron Microscope Imaging:
One representative sample from each subgroup was scanned using
Environmental Scanning Electron Microscope (ESEM)* (Fig. 30) to assess the
surface topography , image s were capture d at magnification of 500X to be
interpreted.

All these measures were done in two phases: before aging phase, and after
aging phase.

* Inspect S, FEI company, US A.
Figure 31: Samples ready for scan

Materials and Methods
60
Aging of zirconia samples:
Samples were aged using a steam autoclave ( Midmark M11 ultraclave
autoclave) * at 134°C with 2 bars pressure and for 8 consecutive cycles (long
cycles of 45 min. each ) that represented more than 5 hours (182).(Fig. 31,32.)

*Midmark .USA.
Figure 30:Midmark M11 Ultraclave autoclave.

Materials and Methods
61

After aging procedure, the second phase of measurements is held with the
same steps discussed earlier as following;
 Color Reproduction Measurements:
With ( VITA Easyshade Compact *)
 Translucency and Opalescence :
With ( Cary 5000 UV –vis–NIR Spect rophotometer†,)
 Enviromental Scanning Electron microscopy:
A representative sample of each group is examined under Environmental
Scanning Electron Microscope‡ with 500X magnification.

* VITA , Zahnfabrik H. Rauter GmbH & Co. KG
† Agilent Technologies Inc., Santa Clara, CA,USA
‡ Inspect S, FEI company, USA .
Figure 30: samples inside autoclave.

Results

36
Statistical analysis:
Statistical analysis was performed with IBM® SPSS® Statistics Version 20
for Windows. Data were presented as mean and standard deviation (SD) values.
Data were explored for normality by checking data distribution, histograms,
calculating mean and median va lues and finally using Kolmogorov -Smirnov and
Shapiro -Wilk tests. (ΔE) data showed non -parametric distribution while (TP) and
(OP) parameters showed parametric distribution.
For non -parametric data; Mann -Whitney U test was used to compare
between the two coloring techniques. Kruskal -Wallis test was used to compare
between surface treatments. Mann -Whitney U test with Bonferroni‘s adjustment
was used for pair -wise comparisons when Kruskal -Wallis test is significant.
Wilcoxon signed -rank test was used to comp are between (ΔE) before and after
aging.
For parametric data; Student‘s t -test was used to compare between the two
coloring techniques. One -way ANOVA test was used to compare between
surface treatments. Tukey‘s post -hoc test was used for pair -wise comparis ons
when ANOVA test is significant. Paired t -test was used to compare between (TP)
and (OP) values before and after aging.
The significance level was set at P ≤ 0.05.

® IBM Corporation, NY, USA.
® SPSS, Inc., an IBM Company.

Results
63
Color reproduction (ΔE)
I ) Effect of coloring technique : (Table .5), (Fig.3 3)
Before aging:
Regardless of surface treatments , dipping technique GP I showed lower
mean (ΔE) (2.39 – 5.53 ±1.04-1.37) than brushing technique GP I I. (9.60 –
13.13 ±0.62-2.45) Mann -Whitney U test showed significant difference. (P ≤0.05)
After aging :
Regardless of su rface treatments , dipping technique GP I showed lower
mean (ΔE) (2. 49- 5.33 ±0.92-1.53) than brushing technique GP II . (8.82-13.39 )
Mann -Whitney U test showed significant difference. (P≤0.05)
Table 5 :Descriptive statistics and results of comparison between ( ΔE) after using the two coloring
techniques tthe
Aging Surface treatment Dipping Brushing
P-value
Mean SD Mean SD
Before
aging Glazing 3.18 1.37 9.57 2.45 <0.001*
Polishing 2.39 1.16 9.60 2.37 0.001*
Polishing + Glazing 5.53 1.04 13.13 0.62 0.001*
After
aging Glazing 3.18 1.53 9.67 2.04 <0.001*
Polishing 2.49 0.92 8.82 1.67 0.001*
Polishing + Glazing 5.33 1.17 13.39 1.12 0.001*
*: Significant at P ≤ 0.05

Results
64

Figure 33: Bar chart representing mean ( ΔE) after using the two coloring techniques
II) Effect of surface treatment : (Table 6), (Fig. 34)
Before aging :
Regardless of coloring technique used , Subgp GP showed the statistically
significant highest mean (ΔE = 5.53 -13.13 ±0.62-1.04) using Kruskal -Wallis test,
Mann -Whitney U test with Benferroni‘s adjustment for pair -wise comparison.
Lower ΔE was with Subgp G (3.18 -9.57±1.37-2.45) and lowest mean was for
Subgp P (ΔE= 2.39-9.60 ± 1.16-2.37) . Kruskal -Wallis test showed no statistical
significance.
After aging
Regardless of coloring technique used, Subgp GP showed the statistically
significant highest mean (ΔE= 5. 33-13.39 ±1.17-1.12) using Kruskal -Wallis test,
Mann -Whitney U test with Benferroni‘s adjustment for pair -wise comparison.
Lower ΔE was with Subgp G (3.18 -9.67±1.53-2.04) and lowest mean was for
0246810121416
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+ Glazing
Before aging After agingMean ( ΔE)
Dipping
Brushing

Results
65
Subgp P (ΔE= 2. 49-8.82 ± 1.67-2.49). Kruskal -Wallis test showed no statistical
significance.
Table 6: Descriptive statist ics and results of comparison between (ΔE) with different surface
treatments
Aging Surface
treatment Glazing Polishing Polishing +
Glazing P-value
Mean SD Mean SD Mean SD
Before
aging Dipping 3.18 b 1.37 2.39 b 1.16 5.53 a 1.04 0.001*
Brushing 9.57 b 2.45 9.60 b 2.37 13.13 a 0.62 0.003*
After
aging Dipping 3.18 b 1.53 2.49 b 0.92 5.33 a 1.17 0.001*
Brushing 9.67 b 2.04 8.82 b 1.67 13.39 a 1.12 0.001*
*: Significant at P ≤ 0.05, Different superscripts in the same row are statistically
significantly different

Figure 34:Bar chart representing mean (ΔE) with different surface treatments
0246810121416
Dipping Brushing Dipping Brushing
Before aging After agingMean ( ΔE)
Glazing
Polishing
Polishing + Glazing

Results
66
III) Effect of aging : (Table .7),(Fig.3 5)
With dipping technique :
Regardless of surface treatments, Wilcoxon signed -rank test showed no
statistically significant difference between mean (ΔE) values before and after
aging.
With brushing technique :
Regardless of surface treatments, Wilcoxon signed -rank test showed no
statistically significant difference between mean (ΔE) values be fore and after
aging.

Table 7: Descriptive statistics and results of comparison between (ΔE) before and after aging
Coloring technique Surface treatment Before aging After aging P-value
Mean SD Mean SD
Dipping Glazing 3.18 1.37 3.18 1.53 0.722
Polishing 2.39 1.16 2.49 0.92 0.726
Polishing + Glazing 5.53 1.04 5.33 1.17 0.511
Brushing Glazing 9.57 2.45 9.67 2.04 0.677
Polishing 9.60 2.37 8.82 1.67 0.441
Polishing + Glazing 13.13 0.62 13.39 1.12 0.399
*: Significant at P ≤ 0.05

Results
67

Figure 35:Bar chart representing mean (ΔE) before and after aging .

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+ GlazingGlazing Polishing Polishing
+ Glazing
Dipping BrushingMean ( ΔE)
Before aging
After aging

Results
68
Translucency (TP)
I) Effect of coloring technique : (Table 8), (Fig.3 6)
Before aging :
Regardless of surface treatment, Student‘s t -test showed no significant
statistical difference between the two coloring techniques .
After aging :
Regardless of surface treatment, Student‘s t -test showed no significant
statistical difference between the two coloring techniques

Table 8: Descriptive statistics and results of comparison between TP after using the two coloring
techniques .
Aging Surface treatment Dipping Brushing P-value
Mean SD Mean SD
Before
aging Glazing 7.41 0.59 7.30 0.64 0.689
Polishing 10.75 0.52 10.91 0.42 0.453
Polishing + Glazing 9.78 0.93 9.26 0.53 0.141
After
aging Glazing 6.06 0.25 5.90 0.37 0.262
Polishing 8.29 0.49 8.44 0.56 0.532
Polishing + Glazing 7.30 0.55 7.06 0.48 0.306
*: Significant at P ≤ 0.05

Results
69

Figure 36: Bar chart representing mean TP after using the two coloring techniques .

II) Effect of surface treatment : (Table . 9), (Fig.3 7)
Before aging :
Regardless of the coloring techniques ,using One -way ANOVA test and
Tukey‘s post-hoc test for pair -wise comparison , Subgp P showed the highest
mean TP (10.75 -10.91 ± 0.42-0.56) . Lower mean TP for Subgp PG (9.26-9.78±
0.53-0.93) . The lowest mean TP was for Subgp G ( 7.30 -7.41 ±0.59-0.64) . all
with statistically significant difference P ≤0.05
After aging :
Regardless of the coloring techniques ,using One -way ANOVA test and
Tukey‘s post -hoc test for pair -wise comparison, Subgp P showed the highest
mean TP (8.29 -8.44 ± 0.42 -0.56). Lower mean TP for Subgp PG (7.06 -7.30 ±
024681012
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+ Glazing
Before aging After agingMean TP
Dipping
Brushing

Results
70
0.55-0.48). The lowest mean TP was for Subgp G ( 5.90 -6.06 ±0.25 – 0.37) . all
with statistically significant difference P ≤0.05 .

Table 9: Descriptive statistics and results of comparison between TP wi th different surface
treatments .
Aging Surface
treatment Glazing Polishing Polishing +
Glazing P-value
Mean SD Mean SD Mean SD
Before
aging Dipping 7.41 c 0.59 10.75 a 0.52 9.78 b 0.93 <0.001*
Brushing 7.30 c 0.64 10.91 a 0.42 9.26 b 0.53 <0.001*
After
aging Dipping 6.06 c 0.25 8.29 a 0.49 7.30 b 0.55 <0.001*
Brushing 5.90 c 0.37 8.44 a 0.56 7.06 b 0.48 <0.001*
*: Significant at P ≤ 0.05, Different superscripts in the same row are statistically
significantly different

Figure 37: Bar chart representing mean TP with different surface treatments .

024681012
Dipping Brushing Dipping Brushing
Before aging After agingMean TP
Glazing
Polishing
Polishing + Glazing

Results
71
III) Effect of aging: (Table 1 0), (Fig.3 8)
With dipping technique :
Regardless of surface treatments, Paired t -test showed there was a
statistically significant decrease in mean TP values (ΔTP = 1.35 -2.48) after
aging.
With brushing technique :
Regardless of surface treatments, Paired t -test showed there was a
statistically significant decrease in mean TP values (ΔTP = 1. 40 -2.47) after
aging.

Table 10: Descriptive statistics and results of comparison be tween TP before and after aging .
Coloring
technique Surface treatment Before aging After aging P-value
Mean SD Mean SD
Dipping Glazing 7.41 0.59 6.06 0.25 <0.001*
Polishing 10.75 0.52 8.29 0.49 <0.001*
Polishing +
Glazing 9.78 0.93 7.30 0.55 <0.001*
Brushing Glazing 7.30 0.64 5.90 0.37 0.001*
Polishing 10.91 0.42 8.44 0.56 <0.001*
Polishing +
Glazing 9.26 0.53 7.06 0.48 <0.001*
*: Significant at P ≤ 0.05

Results
72

Figure 38: Bar chart representing mean TP before and after aging .

024681012
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+ GlazingGlazing Polishing Polishing
+ Glazing
Dipping BrushingMean TP
Before aging
After aging

Results
73
Opal escenc e (OP)
I) Effect of coloring technique : (Table 1 1), (Fig. 39)
Before aging :
Regardless of surface treatments, student‘s t -test showed there was no
statistically significant difference between mean OP values of the two techniques.
After aging :
Regardless of surface treatments, student‘s t-test showed there was no
statistically significant difference between mean OP values of the two techniques .

Table 11: Descriptive statistics and results of comparison between OP after using the two coloring
techniques .
Aging Surface treatment Dipping Brushing P-value
Mean SD Mean SD
Before
aging Glazing 6.95 1.07 6.77 1.14 0.722
Polishing 2.53 0.64 2.86 0.72 0.293
Polishing + Glazing 5.28 1.04 5.74 0.99 0.326
After
aging Glazing 8.42 0.38 8.59 0.28 0.282
Polishing 4.96 0.32 4.88 0.22 0.486
Polishing + Glazing 7.06 0.53 7.27 0.27 0.272
*: Significant at P ≤ 0.05

Results
74

Figure 39:Bar chart representing mean OP after using the two coloring techniques .
II) Effect of surface treatment : (Table 1 2),(Fig.40)
Before aging :
Using One -way ANOVA test and Tukey‘s post-hoc test for pair -wise
comparison showed that ; With dipping technique, Subgp P showed the
statistically significant lowest mean OP (2.53 ± 0.64) . Subgp PG showed
statistically significant higher mean OP (5.28 ± 1.04) . Subgp G showed the
statistically significant highest mean OP (6.95 ± 1.07) .
While with brushing technique; while Subgp P showed the statistically
significant lowest mean OP (2. 86 ± 0.72) there was no statistically significant
difference between Subgp PG and Subg p G; both showed the statistically
signi ficantly highest mean OP values ( 5.74 -6.77 ± 0.99-1.14).

012345678910
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+ GlazingGlazing Polishing Polishing
+ Glazing
Before aging After agingMean OP
Dipping
Brushing

Results
75
After aging :
Regardless of coloring techniques; Subgp P showed the statistically
significant lowest mean OP ( 4.88-4.96 ± 0. 22-0.32). Subgp PG showed
statistically significant higher mean OP ( 7.06-7.27 ± 0.27-0.53). Subgp G
showed the statistically significant highest mean OP ( 8.42-8.59 ± 0.38-0.28).
Table 12: Descriptive statistics and results of comparison between OP wi th different surface
treatments.
Aging Surface
treatment Glazing Polishing Polishing +
Glazing P-value
Mean SD Mean SD Mean SD
Before
aging Dipping 6.95 a 1.07 2.53 c 0.64 5.28 b 1.04 <0.001*
Brushing 6.77 a 1.14 2.86 b 0.72 5.74 a 0.99 <0.001*
After
aging Dipping 8.42 a 0.38 4.96 c 0.32 7.06 b 0.53 <0.001*
Brushing 8.59 a 0.28 4.88 c 0.22 7.27 b 0.27 <0.001*
*: Significant at P ≤ 0.05, Different superscripts in the same row are statistically
significantly different

Figure 40: chart representing mean OP with different surface treatments .

012345678910
Dipping Brushing Dipping Brushing
Before aging After agingMean OP
Glazing
Polishing
Polishing + Glazing

Results
76
III) Effect of aging : (Table 13), (Fig. 41)
With dipping technique :
Regardless of surface treatments, Paired t -test showed that there was a
statistically significant increase in mean OP values (ΔOP= 1.67 -2.43) after aging.
With brushing technique :
Regardless of surface treatments, Paired t -test showed that there was a
statistically significant increase in mean OP values (ΔOP= 1. 53-2.02) after aging.
Table 13: Descriptive statistics and results of comparison between OP before and after aging .
Coloring
technique Surface treatment Before aging After aging P-value
Mean SD Mean SD
Dipping Glazing 6.95 1.07 8.42 0.38 0.002*
Polishing 2.53 0.64 4.96 0.32 <0.001*
Polishing + Glazing 5.28 1.04 7.06 0.53 0.001*
Brushing Glazing 6.77 1.14 8.59 0.28 0.001*
Polishing 2.86 0.72 4.88 0.22 <0.001*
Polishing + Glazing 5.74 0.99 7.27 0.27 0.002*
*: Significant at P ≤ 0.05

Results
77

Figure 41: Bar chart representing mean OP before and after aging .

012345678910
Glazing Polishing Polishing
+ GlazingGlazing Polishing Polishing
+ Glazing
Dipping BrushingMean OP
Before aging
After aging

Results
78

Environmental Scanning Electron Microscopy (ESEM ) Examination :
Colored zirconia surfaces with no surface treatment (Fig. 42):
Showed plain sintered surfaces with a fine -grained structure . Surfaces
showed grinding induced trace -lines with no observed difference between
brushed and dipped samples .

Figure 20: ESEM image x500 of colored zirconia

Results
79
Glazed zirconia surface s:
Before aging (Fig.4 3): surfaces s howed a degree of covering the initia l fine
grained topography but with evident entrapped small granules and air bubbles
inside the glaze layer . No difference between glazed surfaces with both coloring
technique.

Figure 23: ESEM image x500 of glazed zirconia surface
before aging.

Results
80
After aging (Fig.4 4): the major observed difference was that air bubbles
became mo re evident and larger .
No difference between glazed surfaces after aging with both coloring
technique.

Figure 22:ESEM image x500 of glazed zirconia surface after aging .

Results
81

Polished zirconia surface s (Fig.4 5):
The surfaces were apparently more homogenous , the previously appeared
grained topography was eliminated , although few of grinding induced trace
grooves were still evident yet appeared shallower .
No difference was found between polished surfaces of brushed and dipped
samples nor between th e polished surfaces before and after aging .

Figure 25: ESEM image x500 of polished zirconia surface.

Results
82

Polished and glazed zirconia surface s (Fig.4 6):
The initial grained appearance for sintered non treated zirconia surface
appeared more homogenous yet appeared pitted , the glaze layer appeared less
prominent than for the glazed only surfaces with less granular appearance and
less evident air bubbles entrapped inside.
No difference between samples of this group before and after aging.

Figure 26: ESEM image x500 of polished and glazed zirconia surface.

Discussion

33
irconia is helping to usher in a new age of biomimetic dental materials
that are being engineered to emulate the optical, mechanical and
biological characteristics and integrity of natural dentition. While concept of
monolithic zirconia restoration looks very promising mechanically and
biologically, Optimizing the esthetic outcome with such monolithic restorations
has been the greatest challenge to date .
Attaining the target color with monochromatic dyeing in coloring s olution or
customized layering of coloring liquid, is recommended for monolithic zirconia
characterization with no scientific data available on their predictable outcome
(177). With no surface veneering , zirconia surface is either polished or
individual ized by the application of thin glaze layers, afterwards it is ready to
serve in direct contact with oral environmental condition. The long-term stability
of Y -TZP in the presence of water is limited by the continuing transfor mation
from the tetragonal to monoclinic phase, which could raise low -temperature
degradation (LTD) (156). LTD affects microstructure, surface topography which is
expected to have its effect on color, translucency and opalescence as well as
durability.
This study aimed to investigate the effect of coloring techniques, surface
treatments and aging of the material on a three principal determinants of esthetic
outcome; color, translucency and opalescence.
Zirconia samples w ere machine cut with a low speed diamond saw under
coolant a common used cutting procedure in literature . This cutting procedure
showed surface quality near that of CAD/CAM milling as evident by Wang et al
(178) in 2008 who stated that the roughness of saw machine grinding with diamond
coating disc was lower (1.18µm ) than that with CAD/CAM milled (1.91 µm)
with no significant difference. Thus no further treatment before coloring step was Z

Discussion
84
needed. Samples were disc shaped instead of being an atomical for pe rfect
standardization of measuring steps. Beheur F et al (1) mentioned that Discs may
be the more accurate way to measure light translucency as important factors like
size and surface quality can be standardized. Literature was rich with those
studies in which translucency of all -ceramic materials was evaluated using flat
specimens of standardized thickness (7), (179). Besides Hmaidouch et al (118)
pointed out that surface treaetments and polishability were commonly tested in
literature on flat specimens for easier standardization.
The thickness of 1.25 mm was set first in order to allow for 20% -25%
sintering shrinkage , to obtain final thickness of 1 mm dupl icating the final
thickness of monolithic z irconia restorations (180). Thickness was verified by
digital micromet er before and after sintering an error of 0.05mm was allowed
otherwise specimens were excluded and replaced.
The two coloring techniques were selected as being the most recommended
by majority of manufacturers. Parameters of each technique (dipping time and
number of brush strokes) were done according to manufacturer
recommendations. Sintering parameters was set for super speed sintering
program that would result in smallest grain size (177).
For surface finishing; polishing and glazing were mainly selected as the two
main choices for finishing the surface when veneering is excluded. Polishing
before glazing have been recommende d by some autho rs as for glazing alone,
glaze layers at occl usal contacts are known to be worn within the first six months
after insertion of the restorations and the exposed surface should have maximum
smoothness in order not to enhance wear and plaque accumulation (135). For
polishing , intr-oral polishing kit was used to test its efficiency in produce ideal
surface quality as it may become the first option available after chair -side

Discussion
85
adjustments causing ci rcumscribed loss of glaze layer (130) . Brasseler as a trade
mark was commonly used by many authors for polishing surface s and highly –
rated efficiency was reported (123). A standardized controlled four steps polishing
procedure was followed as advised by Al Wahdani and Martin (114) involving
the use of the zirconia polishing kit for polishing and a fine diamond polishing
paste for maximum smoothness . Suitable glaze material was used with matching
coefficient of thermal expansion to be compati ble with zirconia material used .
Autoclave treatment was proven to induce some degree of aging, therefore, it
was a good method to propose an accelerated test for LTD (158). It was suggested
by Chevalier et al that 1h of autoclave at 134 °C had theoretically the same effect
as 3 to 4 years in vivo (166). however, literature debating if this is enough to trigger
t-m transformation , further factors to which zirconia restorations are exposed in
the oral environment (e.g. cyclic mechanical and thermal loading) are not
considered in this calculation; therefore ageing may probably proceed more
rapidly in vivo (156). 10 yea rs was considered a reasonable lifetime for dental
applications, as well as the time it takes for 25% of monoclinic to develop
according to Lughi et al (156) (i.e. the maximum acceptable amount, based on
current international ISO standards (181)). The standard imposes that a maximum
of 25 wt.% of monoclinic is present after an accelerated aging test conducted for
5h at 134 ◦C and 2 bar (181). This was used here in this study for setting aging
parameters. However, this standards does not provide any information about the
actual lifetime at / near room temperature , Lughi et al (156) stated that lifetime
prediction at room or body temperature according to the ISO standards relies on
the assumption that the activation energy is approximately the same for all
stabilized zirconia ceramics —a risky assumption , considering; residual stresses,
grain size and dopant used.

Discussion
86
Two types of spectrophotometers were used in this study, color reproduction
was measured with the VITA Easyshade Compact to resemble clinical situation.
The‖ restoration mode ‖ was used to obtain ΔE between the sample and data set in
its software about shade A2 ., its CIELab output is based on D65 illuminant and
2°degree standard observer, all measurements were done b y the same operator to
minimize error.
For TP and OP a laboratory double -beam spectrophotometer (Cary 5000
UV–vis–NIR Spec trophotometer ), utilizing an integrating sphere attachment , was
used mainly for detection of color parameters in transmission mode . The
wavelength scan in these measurements was carried out from 380nm to 780 nm at
5 nm intervals . In the present study, the increased spectrophotometer‘s window of
19 mm in diameter and the reduced beam size of 1 mm × 5 mm were used to
decrease the edge -loss. In additio n, measurement of diffuse trans mittance was
accomplished using an integrating sphere as an efficient collector of scattered
radiation, since the diffuse transmittance is influenced by the light scattering
character istic in the translucent material . Specular component excluded (SCE)
mode was used in this study, which was pr oved to be more accurate than specular
component included (SCI ) (106) .
TP parameter was chosen instead of CR as it corresponds directly to
common visual assessment of tra nslucency (49). CR is the ratio of the reflectance
of a specimen over a black backing to that over a white backing of a known
reflectance, and is an estimate of the opac ity of a 1 mm thick specimen (50). Since
the translucency of a substance is a function of wavelength (50), the reduction of a
translucency spectrum (wavelength -dependent CR values) to a single parameter
(TP) provides a simpler method to compare translucency (50). Besides Spink et al
(182) concluded that CR, which measures diffuse reflectance, does not detect small
changes in light transmission, when materials present high scattering and

Discussion
87
absorption coefficients. CR could be used only for ceramic materials with a
percent of total transmission of at least 50% (182).
Finally one representative random sample of each tested group were scanned
by environmental scanning electron microscope for providing valuable
information and an idea about the resulting surface topography after different
coloring techniques, surface finishing and aging procedures .
Results of this study showed that : concerning color reproduction; Dipping
technique (GP I) showed significantly lower ΔE values -regardless surface finish
and aging process -than Brushing technique (GP II) which supports that using
dipping technique will provide more predictable results as ΔE values for (GP I)
were between (2.39 -5.53±0.92-1.37). Although these values were in the border
line of perceptibility level s (reviewed in Tabl. 1) or just beyond it, they did not
pass the acceptability zone defined in the same table (Table. 1). For (GP II) all
ΔE values were beyond acceptability level (8.82 -13.13 ± 0.62-2.45). A single
study was found to deal with such coloring technique assessing the effect of
number of layer application by brushing, in which CIE L* a* b* values for all
groups regardless number of layer application were far from those of VITA A2
shade tab (target shade) with a minimum of ΔE=3 reaching 18.7 . This confirms
our results for this t echnique being less predictable.
The less predictability can be explained by less control in standardization of
brushing technique and skill of operator, thus the actual effective concentration of
the coloring liquid was relatively reduced or questioned to be enou gh for
producing the color as Suttor et al (104) mentioned the concentration to be the
primary factor controlling depth of color. Besides questionable depth of
penetration and infiltration of coloring liquid applied by the brush from one
surface only again st the more homogenous and deeper infiltration of the coloring

Discussion
88
liquid with the total immersion of the sample in the coloring solution . Brushed
samples appeared to be less saturated by color which can be detected from higher
L* values, with a less expression of yellowness evident by shift of yellow -blue
axis b* toward blue, and less redness evident by shift of red -green axis a*toward
green. Kim H -K and Kim S -H (106) agreed the previ ous estimated explanation by
proving that increasing number of layer s application of the coloring liquid
resulting in darker specimens (lower L* va lues) and yellowish specimens
(increase b* ) with no significant change in a*. Besides Tuncel et al (183) in
another study found that coloring method may affect the intensity of the shade.
Polishing (Subgp P) in either group had the lowest ΔE values (2.39 -9.60 ±
0.92-2.37) among the other surface finish techniques while glazing (Subgp G)
showed higher ΔE (3.18 – 9.67 ± 1.37-2.04) with no statistically significant
difference. These results support the idea that surface topography affects the
appearance of ceramic material. SEM analysis revealed minimal surface
characterization and defect -free appearance -except for few faint trace lines – for
polished specimens compared to the relatively irregular glazed surface with
evident air bubbles that may be trapped during mixing and may have modified
the reaction with light thus affect the color . According to many authors (110) , (113) ,
(114), if the object has a smooth surface, the light is reflected in a narrow cone
centered about the angle of reflectance. An increasingly roughened surface would
reflect the individual segments of the specular beam at slightly different angles in
a diffused pattern and that would affect the color. Further investigation and
measuring the exact effect of used surface finishing procedures in the present
study on the surface roughness of monolithic zirconia is highly recommended.
Obregon et al (111) demonstrated that different surface textures produced
significant differences in hue, chroma and value pointing out that value
represented the most significant changes following the modification of surface

Discussion
89
texture with the smooth surface increasing the value and this was proved also by
Chung (115), Lee et al (184) and Kim et al (185) in different studies. In addition the
same study of Obregon et al (111) concluded there was a shift in hue toward the
yellow red scale with the highly glazed surface s supported by Kim et al (185) by
recording an increase in CIE a* and b*with glazed surfaces . They claimed that
glazing procedure demonstrated more color deviation which might be related
with any chemical br eakdown at elevated temperature . In the present study
additio nal glazing firing might have cause d any structural changes of monolithic
zirconia that may cause shift in color parameters in a way or another . This needs
to be evaluated in further investigations . However in th e present study, the
difference between polished and glazed was statistically not significant .
As for polished then glazed group (Subgp PG) the significantly highest ΔE
values were found (5.33 -13.39 ± 0.62-1.17). This can be explained under the light
of Obregon et al (111) study by the allied effect of polishing in increasing the
value as added to the effect of glaze in modifying the hue as described earlier .
Complete wetting of the surface by the glaze material is questioned as a certain
degree of roughness usually is prerequisite to increase wetting and bond between
zirconia surfa ce and applied porcelain on top (61), voids between the glaze layer
and zirconia surface may therefore increase scattering of light modifying the
resultant color .
Effect of aging on color reproduction appeared negligibl e in this study,
although structural and surface alterations were estimated to take place with an
impact on light interaction and a perceptible shift in color. This may be related to
the sensitivity and accuracy of the VITA Easyshade Compact used for detecti on
of color change, or to the questionable amount of structural and superficial
alteration of aged zirconia samples as a result of the used aging protocol . Further
investigations on microstructural changes upon aging and its effect on specimen‘s

Discussion
90
surface th rough uplifts or gains pull -out as estimated, beside the effect on Oxygen
vacancies that represent the coloring centers in zirconia, will be beneficial for
clear explanation.
Considering translucenc y and opalescence ; In the present study, th e TP
values of monolithic zirco nia were measured using the specimens of approx. 1
mm in thickness, showing the range from (5.90 – 10.91 ± 0.25-0.93 ) this range is
lower than that reported by Kim H -K and Kim S -H (106) with another zirconia
material (Bruxzir ) of even large r sample thickness of 2mm ranged from 9.15 to
11.69 , a higher TP range for three different zirconia materials was recorded by
Pecho et al (49) as (17.2 ± 1.8) with no statistical significant difference than that of
human and bovine dentin. While opalescence parameter recorded in this study
was in the range of (2.53 – 8.59 ± 0.02 – 1.14 ), literature reported that OP values
of bovine enamel of 0.7 –1.1 mm in thickness ranged from (7.6 to 22 .7), which
was varied by the con figuration of spectrop hotometers , and those of human
enamel of 0.9 –1.3 mm in thickness ranged from (19.8 to 27.6 ) (186). In one study
to investigate the opales cence of materials using a spec trophotometer , the range
of OP value was 1.6 –6.1, 2.0 –7.1,1.3 –5.0 and 1.6 –4.2 for the core, veneer, A2 –
and A3 -layered specimens, respectively, and all of which were significantly
influenced by the type of materials (56). It was reported (57) that the OP value,
which can contribute the vitality of dental restorative composites, is at least \9.
Kim H -K and Kim S -H (106) stated that the restorative materials with OP values
of between 4 and 9 may be considered to have some opal escence only slightly
discernible to the naked eyes. In the present study, all specimens recorded OP
below 9 which acc ording to previous studies (57), (106) is considered non -opalescent
can‘t contribute opalescence to the tooth vitality appearance. This may be due to
low light transmittance as opalescence mainly requires a translucent material that
pass long wave -length and scatter the short wave length. The material tested here

Discussion
91
didn‘t transmit light to a high degree as maximum luminous trans mittance was
found to be 18.85% .
Coloring techniques in this study had no effect on translucency neither on
opalescence of the material. For translucency, this is consistent with results of
other studies referred translucency to inherent variables in material processing
rather than coloring procedure . Pecho et al (49) found no signific ant dif ferences
between TP values of non-colored and colored zirconia systems . They showed
that t he translucency of a material depends on the scattering and absorption
coefficients as well as on the thickness of the sample . Kim H -K and Kim S -H
(106) stated about translucency ―it cannot be controlled by the coloring procedure.
The translucency would rather result from inherent variables by regulating the
preparation method of raw material, a dditional processing techniques and
sintering conditions ”. Therefore , understanding of monolithic zirconia
translucency should be taken into account at the time of material selection. For
opalescence , coloring did not appear to modify the scattering behavior of the
material, analytical studies in literature revealed a low concentration of coloring
elements as it was rarely observed even through XRD (90) of colored zirconia
samples, therefore it is logic not to affect opalescence.
Polished samples (Subgp P) regardless the coloring technique and aging
process showed the high est translucency ( highest TP values = 8.29 – 10.91 ±
0.42- 0.56) over the two other groups , these values were supported by Beuer F
et al (1) where polished full contour zirconia samples recorded higher
translucency than glazed ones. As only one interface (air –zirconia) refracting the
light is present, less attenuation of light transmission, compared to the other
groups, can be assumed. Other tested groups exhibited more interfaces: glazed
full-contour zirconia (air –glaze; glaze –zirconia). Meanwhile, even polishing
before g lazing (Subgp PG) increased the translucency more than the glazed

Discussion
92
alone (Subgp G) , this may be referred again to difficult wetting of the glaze to
the smo othed polished zirconia s urface resulted in a thinner layer of glaze to
cover zirconia surface thus allowed more transmission , besides the effect of
polishing in remo ving almost all deep surface defects –as appeared through SEM
imaging – that may attenuate light path .
As for opales cence, polished samples (Subgp P) in all conditions tested
recorded the lowest OP parameter values (2.53 – 4.96 ± 0.22-0.72) explained
apparently by low or no adding scattering cites . While irrigularities , particles and
air bubbles inside glaze layer definitely increase d scattering led to increased OP
value s for (Subgp G) to (6.77 -8.59 ± 0.28-1.14) . Glazing over polished surface
(Subgp GP) again was in between the polished and the glazed which is
coincident in all conditions with significant difference except in only one
condition in (GPII GP) before aging procedure showed no significant difference
than (GPII G) this may be attributed to difficulty in achieving uniform degree of
glazing.
Aging had significantly affect ed the translucency and opalescence in the
present study regardless coloring technique and surface finishing procedure. The
accelerated aging protocol in the present study was according to ISO standards
expecting that effective transformation with a maximum of 25% t -m
transformation (181) occurred which w ould most probably cause modifications in
microstructure such as; release of small zirconia grains , grain s pull -out, surface
uplifts and surface roughening with one of previously discussed mechanisms (156).
This may be the most accepted reason behind decreased transmittance and
increased scattering centers. Further analysi s wit h advanced imaging and
microstructure analysis may be beneficial to confirm such assumptions .

Discussion
93
The results of this study apply to one zirconia material provided by a single
manufacturer. Different zirconia materials may show different composition ,
microstructure, and initial grain size may have affected the esthetic outcome
differently (106). Moreover, a single sintering program regarding temperature,
heating rate and s intering atmosphere was tested, differ ence in sintering
conditions may influence microstructure, longevity, hydrolytic performance,
resulting grain sizes, surface properties and LTD resistance (8).A single shade
(A2) is tested and different results may be obtained with different shades.
Coloring liquid application through both techniques was done according to
manufacturer instructions however; modifying any of these parameters may have
its impact on the results (106). A single kind of polishing kits and p olishing pastes
was used in a definite manner which is not a constant and their modification can
modify the outcome (119). A specific glaze material and glazing procedure was
followed , although the degree of glossiness after glazing can be controlled eithe r
by firing time or by furnace temperature (114). So modification of color after
glazing might be different according to different procedures and firing protocol .
Uniform degree of glazing on the specimens‘ surface was difficult to achieve and
is sensitive . Temperature fluctuations inside the furnace might affect the results
(114). Different accelerated aging protocols also may affect results differently.
Two different spectrophotometers were used for measuring different variables ;
the VITA Easyshade Compact being clinically used to simulate clinical
situation in detecting ΔE between obtained and target shade, however, it is not
able to detect transmittance values and edge -loss is not controlled. Laboratory
spectrophotometer Cary 5000 UV – vis-NIR was used for calculating parameters
in the transmission mode.

Summary &
Conclusio ns

49
sthetic demand is increasing for monolithic zirconia (MZ) restorations.
Fabrication of monolithic restorations with an appropriate shade,
translucency and opalescence is critical for matching to the neighboring teeth and
for a natural -looking appearance . Coloring techniques serving to shade
monolithic zirconia efficiently had no evidence -based results for optimizat ion.
Moreover , the way for attaining an ideal surface decreasing biofilm
accumulation, wear and enhancing esthetics is not established nor defined up to
date. Even after b est matching of natural looking, Zirconia aging should always
been considered especia lly when it comes to monlithic zirconia with no veneer on
top.
This study was held to assess color reproduction, tr anslucency and
opalescence of m onolithic zirconia after two different coloring techniques, th ree
surface finishing procedures , before and aft er aging.
Sixty monolithic zirconia (MZ) plates (19 ×15×1.25 mm) were machin e cut
from the zirconia blocks (InCoris TZI blocks , Sirona Dental Systems (SDS)
GmbH , Bensheim, Germany. 40×19×15 mm), the plates were divided into two
groups according to coloring technique; GPI (n=30) colored by dipping
technique with (inCoris TZI coloring liquid A2 (SDS) ) for 5 min. according to
manufacturer instructions , while for GPII (n=30) (inCoris TZI coloring liquid
A2 (SDS)) was applied to the surface with a brush for 5 brush strokes . Sintering
was done in the Sirona inFire HTC speed (SDS) furnace with ―Super Speed‖
program preset in furnace. After sintering, Ten zirconia plates of each group were
either; glazed Subgp G, polished Subgp P or polished then glazed Subgp PG.
In Subgp G, specimens were glazed using ( VITA AKZENT glaze powder
and fluid VITA (VT), Zahnfabrik H. Rauter GmbH & Co. KG ) mixed till
creamy mix is obtained a pplied with suitable brush in one brush stroke s in one E

Summary and conclusions
95
direction then fired in Programat P300 furnace Ivoclar Vivadent (IV),
Schaan, FL . While for Subgp P specimens were polished with a sequence of
three diamond burs ; coarse, medium and fine (K0262 Dialite ZR intra -oral
adjustment finishi ng and polishing system . Brasseler (Br) USA ) followed by
applying diamond polishing paste (Zi- polish, bredent, GmbH & Co.KG (br))
with application brush (Wheel Brush Rodeo . (br)) which is double loaded with
natural horse hair . Each step was done for 60 seconds with a total of 4 mins. p er
sample. Finally for Subgp PG polished with the same sequence of the polishing
kit without use of diamond paste and then the glaze was applied by the same
described manner. Accelerated aging in a steam autoclave (M 11 ultraclave
autoclave . Midmark USA. (MD)) for 8 consecutive cycles in 134 °C 2 bar
pressure.
Measurements for color reproduction of shade A2 ( Δ E) were done using
(VITA Easyshade Compact (VT)) spectrophotometer while for translucent
parameter TP and opalascent parameter OP a laboratory spectrophotometer with
integrating sphere (Cary 5000 UV – vis-NIR Agilent Technologies (AT) Inc.,
Santa Clara, CA,USA ) was used.
The results of color reproduction with VITA Easyshade Compact (VT)
were : GP I showed significantly lower Δ E than GP II regardless of surface
finish and aging process. Subgp P showed lowest ΔE values followed by Subgp
G with no statistical significance, and the significantly highest ΔE values were
for Subgp PG in all conditions. Aging had no effect on color reproduction.
Results of translucency and opalescence as measured with Cary 5000 UV –
vis-NIR (AT) showed that: coloring technique had no effect on translucency nor
opalescence. Aging, regardless coloring technique and surface finishing
procedure, decreased (TP) values led to a less translucent material and increased

Summary and Conclusions
96
(OP) values significantly . For surface finish inverse relation between their effect
on TP and on OP values as; while Subgp P showed the highest TP value
regardless of other variables, it showed the lowest OP values. The exact opposite
was with Subgp G where the lowest TP values and highest OP values were
reported. Subgp PG was in between in all tested conditions.
CONCLUSIONS:
Within the limitations of the present study the following can be concluded:
1) Dipping coloring technique is more reliable and predictable for monolithic
zirconia restorations than brushing technique in terms of shade reproduction.
2) Negligible effect of coloring technique on translucency and opalescence was
observed .
3) Polishing can optimize the c losest shade matching, best surface defects
elimination , least scattering and best translucency over either glazing or
glazing after polishing treatmen t.
4) Glazing enhanced scattering, decreas ed translucency and shifte d the target
shade .
5) No esthetic benefit gained when monolithic zirconia surface is polished
before glazing in terms of color reproduction although an improvement in
translucency over the gla zing alone is obtained .
6) Aging although triggering no color shift, they had tendency to affect esthetic
outcome through decreasing translucency and increasing opacity significantly
for monolithic zirconia restoration s.
7) In all -situations tested , zirconia material in the tested thickness exhibited low
translucency and opalescence, making its application in highly esthetic
demanding situations a contraindication .

Summary and conclusions
97
Clinical Implications:
For a perfect color match of monolithic zirconia restoration, clinicians
should take into account the possible deviations after polishing or glazing at the
time of shade selection. Furthermore, different shade guides considering any
color changes following surface treatments can be helpful for monolithic zirconia
restorations in clinical matching protocols.
According to this study design, this material in this thickness is not suitable
whenever high translucency and opalescence is needed. Dipping coloring
technique is highly recommended for more predictable results. Polishing rather
than glazing is recommended for uniform defect -free surface with more
predictable shade matching and highest translucency possible. Aging although
have negligible effect on color stability, its effect on decreasing translucency and
increas ing opacity should be highly considered clinically.

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Appendix

Sample no. B* A* Sample no. B* A* Sample no. B* A*
1 0.6 0.3 21 4.8 4.2 41 7.2 7.9
2 0.5 0.4 22 2.1 1.9 42 6.2 6.8
3 2.6 1.9 23 2.0 3.0 43 4.8 5.0
4 4.6 4.9 24 1.3 1.6 44 5.6 5.3
5 3.6 3.0 25 1.9 2.5 45 5.1 4.8
6 5.4 5.5 26 1.7 1.9 46 5.8 5.5
7 2.4 3.6 27 1.3 1.8 47 7.3 7.6
8 3.4 3.6 28 2.4 1.7 48 6.5 4.6
9 3.3 2.9 29 3.3 3.2 49 4.3 4.4
10 2.7 2.9 30 3.8 3.5 50 4.2 4.0
11 9.0 12.0 31 11.2 8.7 51 14.8 13.6
12 11.9 11.7 32 10.1 11.1 52 13.6 12.6
13 6.1 6.8 33 12.6 9.5 53 12.2 13.9
14 11.8 10.8 34 7.5 6.9 54 13.0 12.5
15 9.5 8.3 35 12.4 8.4 55 12.9 12.4
16 13.1 12.3 36 6.5 6.0 56 13.8 14.9
17 6.8 7.6 37 6.3 8.2 57 12.6 12.6
18 10.4 9.6 38 9.6 10.3 58 13.8 14.8
19 11.9 11.4 39 10.2 10.3 59 12.8 13.9
20 7.5 8.2 40 11.3 11.1 60 11.0 12.5
B* : Before Aging
A* : After AgingPolished + GlazedDipped BrushedΔE ValuesBrushed DippedGlazed
Dipped BrushedPolished

Sample no. B* A* Sample no. B* A* Sample no. B* A*
1 7.5 6.1 21 10.1 8.3 41 10.7 7.8
2 6.2 6.0 22 10.3 8.5 42 8.5 7.3
3 7.6 5.8 23 10.6 9.2 43 10.1 6.5
4 7.9 5.9 24 10.8 7.7 44 9.0 6.8
5 6.8 5.8 25 10.9 8.7 45 9.3 8.1
6 7.0 6.2 26 10.8 7.7 46 8.6 7.0
7 8.0 6.4 27 10.0 8.0 47 9.9 7.1
8 8.0 5.9 28 11.1 8.8 48 9.9 8.1
9 7.4 6.6 29 11.3 8.0 49 11.1 7.4
10 7.7 6.0 30 11.5 8.1 50 10.8 7.0
11 7.6 6.0 31 10.6 7.8 51 9.0 7.5
12 7.5 5.4 32 10.0 9.3 52 9.2 6.8
13 6.6 6.4 33 11.1 8.8 53 9.1 7.7
14 5.9 6.2 34 10.8 8.0 54 8.8 6.6
15 6.9 5.9 35 10.7 7.7 55 9.8 7.7
16 7.6 6.2 36 10.9 8.7 56 10.0 7.4
17 8.1 6.1 37 11.2 8.1 57 8.3 6.9
18 7.5 5.3 38 11.4 8.7 58 9.5 7.0
19 7.6 5.9 39 11.3 8.2 59 9.8 6.4
20 7.6 5.5 40 11.1 9.0 60 9.2 6.6
B* : Before Aging
A* : After Aging
Brushed
Brushed
BrushedTP Values
Glazed Polished Polished + GlazedDipped
Dipped
Dipped

Sample no. B* A* Sample no. B* A* Sample no. B* A*
1 6.1 9.1 21 2.4 5.1 41 6.0 6.3
2 5.9 7.7 22 2.6 4.9 42 5.8 7.8
3 6.4 8.7 23 2.5 4.8 43 6.3 7.5
4 9.1 8.4 24 3.1 4.7 44 4.5 7.0
5 6.5 8.6 25 2.4 5.4 45 5.5 7.0
6 6.4 8.1 26 2.1 5.0 46 5.5 6.2
7 6.3 8.3 27 1.4 4.6 47 6.1 7.0
8 8.2 8.2 28 2.7 5.5 48 4.4 7.7
9 7.9 8.7 29 2.2 4.9 49 5.9 7.1
10 6.7 8.4 30 3.9 4.7 50 2.9 7.1
11 6.3 8.5 31 1.9 5.0 51 6.9 7.3
12 6.2 8.1 32 3.9 4.5 52 5.5 7.4
13 6.8 8.9 33 3.1 4.9 53 4.5 7.1
14 7.4 8.7 34 4.0 4.6 54 6.7 6.7
15 6.1 8.7 35 1.9 5.0 55 7.0 7.3
16 5.7 9.0 36 2.6 4.7 56 6.2 7.4
17 4.9 8.6 37 2.7 5.0 57 4.5 7.5
18 8.2 8.2 38 2.7 5.2 58 5.3 7.0
19 7.7 8.6 39 3.2 5.1 59 4.6 7.7
20 8.4 8.5 40 2.5 4.8 60 6.2 7.4
B* : Before Aging
A* : After Aging
Brushed
Brushed
BrushedOP Values
Glazed Polished Polished + GlazedDipped
Dipped
Dipped

Sample no. L a b L a b L a b
1 75.01 -0.17 10.75 81.03 2.44 14.37 49.20 1.99 16.43
2 73.82 -0.18 9.41 78.74 2.14 12.32 47.98 2.10 14.89
3 74.68 -0.20 9.68 81.13 2.22 12.98 48.03 2.01 15.66
4 72.54 -0.27 9.41 78.81 2.61 13.34 48.18 2.11 18.24
5 73.60 -0.18 10.66 78.10 1.98 15.30 47.90 2.23 16.68
6 73.53 -0.25 9.61 78.78 1.86 13.69 48.53 1.95 15.66
7 75.13 -0.28 9.42 81.78 1.71 13.32 48.87 1.71 15.35
8 74.49 -0.31 10.63 81.25 1.94 14.19 48.22 1.62 18.57
9 73.12 -0.13 9.55 79.07 2.15 13.38 48.49 2.23 17.04
10 74.50 -0.28 10.44 80.57 2.13 14.60 47.64 1.95 16.79
11 73.68 -0.22 9.93 80.02 1.79 13.61 49.07 1.63 15.90
12 73.71 -0.31 10.45 79.21 2.08 14.99 47.95 1.38 16.39
13 75.55 -0.23 10.81 80.81 1.89 14.10 49.10 1.82 17.33
14 74.65 -0.21 10.55 78.81 2.00 14.18 48.65 1.71 17.74
15 74.99 -0.30 11.53 80.40 1.72 15.33 48.96 1.74 17.23
16 75.57 -0.32 11.12 82.23 1.93 14.12 49.29 1.91 16.36
17 74.73 -0.29 10.99 81.19 2.63 15.00 49.11 1.85 15.45
18 75.17 -0.23 9.84 81.04 2.49 13.65 48.49 1.84 17.73
19 75.33 -0.24 10.26 81.23 2.58 14.07 48.85 2.10 17.61
20 75.91 -0.15 10.42 81.73 2.54 14.52 48.20 1.84 18.61CIE L a b Parameters of Glazed Samples Before AgingBrushedAgainst White Transmitted Against BlackDipped

Sample no. L a b L a b L a b
21 70.50 -0.47 6.64 77.29 2.16 14.78 49.85 0.62 8.80
22 69.61 -0.46 6.82 76.74 2.07 15.45 50.28 0.72 9.13
23 68.33 -0.60 6.79 75.59 0.98 14.67 50.90 0.53 9.05
24 69.94 -0.49 6.45 76.67 1.65 14.62 50.42 0.62 9.30
25 67.60 -0.53 8.61 74.68 1.72 16.60 50.89 0.60 10.75
26 69.55 -0.78 8.99 77.36 1.58 16.04 50.34 0.42 10.66
27 70.23 -0.61 9.39 77.03 1.81 16.24 50.39 0.55 10.25
28 69.52 -0.76 7.82 77.27 1.66 14.26 51.35 0.39 10.27
29 70.32 -0.81 8.42 77.52 1.61 15.18 51.31 0.38 10.26
30 71.51 -0.57 7.06 79.69 1.45 14.68 51.38 0.53 10.79
31 69.83 -0.67 8.57 76.58 1.74 16.40 50.78 0.33 10.19
32 70.95 -0.89 8.69 77.57 1.17 15.86 51.56 0.17 12.47
33 69.29 -0.77 8.23 76.64 1.48 16.20 49.70 0.24 11.17
34 69.20 -0.87 5.67 75.92 0.92 13.93 50.98 0.21 9.53
35 71.30 -0.85 7.77 78.04 0.44 16.00 50.65 0.21 9.39
36 68.65 -0.73 8.24 76.51 1.46 15.42 49.68 0.49 10.53
37 69.26 -0.68 8.57 77.27 1.09 16.14 50.20 0.43 11.04
38 70.36 -0.48 6.75 78.86 1.74 14.09 50.67 0.73 9.15
39 69.44 -0.84 7.08 77.02 1.40 15.13 50.61 0.16 10.16
40 70.95 -0.76 8.63 78.31 1.24 16.72 50.12 0.47 10.81CIE L a b Parameters of Polished Samples Before AgingBrushedAgainst Black Against White TransmittedDipped

Sample no. L a b L a b L a b
41 73.11 -0.30 8.22 81.41 1.54 14.69 50.56 1.31 14.01
42 72.17 -0.33 8.91 78.39 1.74 14.25 50.00 1.06 14.55
43 73.28 -0.28 8.25 80.33 2.00 15.06 49.95 1.26 14.34
44 71.75 -0.21 8.90 78.44 1.46 14.69 50.64 1.13 13.23
45 71.87 -0.27 8.38 79.02 1.72 13.93 49.45 1.22 13.64
46 72.85 -0.29 8.48 78.32 1.84 14.74 50.20 1.12 13.78
47 72.69 -0.28 8.91 80.99 1.48 14.05 50.27 1.34 14.74
48 70.68 -0.30 9.73 78.26 1.72 15.81 49.73 1.39 13.78
49 70.18 -0.39 8.91 79.01 1.78 15.27 49.96 1.58 14.46
50 71.97 -0.23 9.98 80.27 1.51 16.74 49.27 1.20 12.53
51 70.32 -0.27 6.97 77.35 2.07 12.06 49.28 0.97 13.72
52 72.03 -0.36 8.10 78.20 2.09 14.48 49.90 1.17 13.39
53 71.53 -0.29 8.71 77.28 1.85 15.40 50.21 1.51 12.87
54 71.58 -0.33 7.75 78.62 1.69 12.58 50.14 1.03 14.33
55 72.39 -0.33 7.35 79.61 1.35 13.72 49.52 1.43 14.17
56 72.96 -0.40 8.06 80.92 1.81 13.77 49.94 1.26 13.99
57 72.55 -0.39 8.87 78.71 1.13 14.22 49.81 1.33 13.04
58 71.91 -0.41 8.76 79.65 1.44 13.87 48.88 1.27 13.76
59 73.25 -0.27 8.86 80.33 1.95 15.30 49.63 1.20 13.22
60 71.27 -0.25 7.72 77.64 1.87 13.98 48.95 1.27 13.76Against Black Against White TransmittedCIE L a b Parameters of Polished and Glazed Samples Before AgingBrushed Dipped

Sample no. L a b L a b L a b
1 72.35 0.16 13.56 77.54 2.32 15.95 45.09 4.09 21.72
2 70.42 0.26 11.79 74.97 2.32 15.04 46.07 3.72 18.67
3 71.74 0.12 12.33 76.13 2.29 15.49 44.92 4.26 19.96
4 69.42 0.07 11.68 74.34 2.08 14.15 45.43 3.79 19.17
5 70.17 0.14 12.95 74.79 1.73 16.05 44.74 4.02 20.65
6 69.93 0.05 12.16 75.17 1.91 14.89 45.36 3.38 19.54
7 72.28 0.10 11.93 77.66 2.25 14.54 45.22 3.57 19.49
8 70.81 0.04 12.63 75.35 2.01 15.87 45.51 4.02 19.84
9 69.65 0.34 11.48 75.06 2.49 14.49 45.73 4.39 19.22
10 71.25 0.07 12.45 76.21 1.75 15.39 45.47 3.83 19.97
11 70.67 0.07 12.55 75.65 1.88 15.28 44.68 3.45 20.39
12 70.63 0.10 13.15 74.99 2.19 15.58 44.26 3.97 20.31
13 72.26 0.16 13.03 77.60 1.89 16.04 45.55 3.54 21.30
14 71.11 0.11 12.43 76.13 1.89 15.61 45.46 3.68 20.34
15 72.18 -0.05 14.07 77.12 1.69 16.71 45.22 3.86 21.89
16 72.46 -0.01 13.12 77.59 1.56 16.30 45.20 4.09 21.15
17 71.73 0.03 13.03 76.73 1.91 16.04 46.08 3.32 20.93
18 72.41 0.11 12.29 76.81 1.83 14.79 45.16 3.91 19.51
19 72.44 0.08 12.02 77.27 2.02 14.89 44.99 4.03 19.67
20 73.00 0.20 12.01 77.70 1.84 14.36 45.28 3.88 19.68DippedCIE L a b Parameters of Glazed Samples After Aging
Against Black Against White TransmittedBrushed

Sample no. L a b L a b L a b
21 68.54 0.31 8.05 75.12 1.77 12.97 48.21 2.25 12.81
22 67.24 0.44 8.07 74.25 2.01 12.62 48.73 2.29 12.60
23 65.59 0.11 8.00 72.67 1.52 13.65 48.26 1.82 12.50
24 68.07 0.26 7.70 74.06 2.09 12.13 47.71 2.36 11.86
25 65.01 0.28 10.11 71.64 1.50 15.56 48.26 2.34 15.15
26 67.21 0.08 10.65 72.90 1.46 15.68 49.10 2.23 15.11
27 67.48 0.35 10.98 73.00 1.66 16.55 47.76 2.15 15.18
28 67.96 0.06 9.07 75.06 1.56 13.99 47.50 2.32 14.11
29 67.94 0.17 9.93 74.25 1.53 14.74 48.43 2.32 14.37
30 69.57 0.36 8.23 76.16 1.92 12.60 48.84 2.32 12.53
31 67.62 0.14 9.83 73.45 2.05 14.64 49.46 2.00 14.45
32 68.91 0.12 10.22 76.60 1.60 15.30 48.71 2.13 14.27
33 66.93 0.19 9.56 74.36 1.93 13.99 48.65 2.14 14.05
34 67.07 0.01 7.08 73.48 1.44 11.56 49.32 1.96 11.28
35 68.87 0.09 9.11 74.39 1.50 14.25 48.60 2.13 13.69
36 66.24 0.03 9.53 72.50 1.67 15.34 48.98 2.11 13.69
37 66.77 0.23 10.00 73.23 1.85 14.69 48.91 2.05 14.66
38 67.82 0.60 8.14 74.55 1.91 13.57 48.57 2.68 12.91
39 66.93 0.09 8.58 73.32 1.47 13.51 48.16 2.04 13.29
40 68.87 0.16 10.15 75.85 1.44 15.75 49.10 2.26 14.44DippedCIE L a b Parameters of Polished Samples After Aging
Against Black Against White TransmittedBrushed

Sample no. L a b L a b L a b
41 70.76 0.45 9.97 77.41 1.90 13.79 46.51 3.30 15.58
42 69.16 0.31 10.38 75.42 1.48 13.95 46.48 4.13 17.13
43 70.74 0.31 9.75 76.22 1.66 12.88 47.07 4.11 16.17
44 69.04 0.28 10.49 74.04 1.96 14.72 46.81 3.51 16.68
45 68.84 0.38 9.79 75.73 1.74 13.81 46.65 3.33 16.10
46 69.65 0.42 10.12 75.26 1.53 14.09 47.08 3.57 15.44
47 70.24 0.32 10.44 76.34 1.48 13.95 47.11 3.59 16.60
48 67.40 0.28 11.08 73.82 1.55 15.84 46.67 3.72 18.02
49 67.11 0.28 10.48 73.22 1.54 14.54 46.13 3.51 16.75
50 69.21 0.39 11.57 74.99 1.78 15.30 46.01 3.89 17.80
51 67.49 0.26 8.33 73.81 1.26 12.26 46.97 3.60 14.78
52 69.62 0.29 9.44 75.30 1.31 13.09 46.26 3.78 16.00
53 68.43 0.26 10.40 75.11 1.57 14.05 46.63 4.42 16.11
54 68.72 0.25 9.31 74.37 1.51 12.58 46.12 3.42 15.23
55 69.57 0.30 8.80 76.02 1.35 12.84 46.14 4.17 14.96
56 70.01 0.21 9.21 76.33 1.50 12.82 46.49 3.87 15.60
57 69.69 0.08 10.08 75.43 1.91 13.39 46.43 3.50 16.70
58 69.47 0.24 9.81 74.76 1.48 14.16 45.76 3.54 16.03
59 70.54 0.25 10.82 75.74 1.57 14.38 45.60 3.65 17.69
60 68.55 0.26 9.35 74.12 1.24 12.68 45.77 3.75 15.91TransmittedDippedCIE L a b Parameters of Polished and Glazed Samples After AgingBrushedAgainst Black Against White

Sample no. B* A*
Mean 14.67 13.36
±SD 0.86 0.57
Mean 14.18 13.11
±SD 0.71 0.70
Mean 18.85 17.17
±SD 0.64 0.64
Mean 18.51 17.08
±SD 0.75 0.68
Mean 17.06 14.65
±SD 0.81 0.46
Mean 16.27 14.06
±SD 0.77 0.61
B* : Before Aging
A* : After AgingLuminous Transmission
Dipped
BrushedPolished1-10
11-20
21-30
31-40Dipped
Brushed
DippedGlazedPolished +
Glazed21-30
31-40Brushed

Arabic
Summary

الملخص العربي
7. ححج كم ظشٔف انقٍاط فً ْزا انبحذ ٔفً ظم انغًك انًغخخذو، الحعذ انضسكٍَٕا
كايهت انكفاف يادة يُاعبت نهحاالث شذٌذة االحخٍاس نهض ًانٍاث.

الملخص العربي
القياساث:
حى قٍاط أبعاد انهٌٕ ٔخاطٍت انشبّ شفافٍت بٕاعطت صٓاص قٍاط طٍف سقًً.
التعتيك:
حى حعخٍق انعٍُاث داخم صٓاص األٔحٕكالف عُذ دسصت حشاسة ٢01° عهٍضٌٕط نزًاٌ
دٔساث طٌٕهت يخخانٍت ، ٔحكشاس صًٍع انقٍاعاث بعذ عًهٍت انخعخٍق.
التذليل اإلدصائي:
حى ححهٍم انًعطٍاث باخخباساث ئحظائٍت يخخهفت نخحهٍم انُخائش ئحظائٍا.
نتائج البذث:
يٍ َخائش انبحذ حى اعخُخاس ياٌهً:
٢. انخهٌٍٕ بطشٌقت اإلغًاس فً انظبغت أحادٌت انهٌٕ حعذ طشٌقت يٕرٕقت بانُغبت
نهخشيًٍاث انضسكٍَٕت كايهت انكفاف.
٥. طشٌقت انخهٌٍٕ نٍظ نٓا حأرٍش يهحٕظ عهى خاطٍت شبّ انشفافٍت ٔخاطٍت انبشٌق.
0. انخهًٍع أقذس عهى احقاٌ يٕافقت انهٌٕ،ٔئضفاء عطحا يخضاَغا ، حقهٍم االَخشاس انضٕئً
ٔصٌادة خاطٍت انشبّ شفافٍت أكزش يٍ انخضصٍش أٔ انخضصٍش بعذ انخهًٍع.
1. انخضصٍش ٌضٌذ يٍ عذو اعخٕاء انغطح،ٌٔضٌذ حشخج انضٕء ، ٌٔقهم انشبّ شفافٍت
ٌٔحذد حغٍٍشا فً دسصت انهٌٕ انًطهٕبت
2. نى حضُى أي فائذة صًانٍت يٍ انخهًٍع قبم انخضصٍش نغطح انضسكٍَٕا كايهت انكفاف.فًٍا
ٌخض يطابقت انهٌٕ ، بانشغى يٍ انخح غٍ انطفٍف فً خاطٍت شبّ انشفافٍت.
3. سغى عذو حأرٍش انخعخٍق عهى دسصت انهٌٕ ٔنكٍ نّ حأرٍش عهى انُخٍضت انضًانٍت يٍ خالل
حأرٍشِ عهى خاطٍت انشبّ شفافٍت ٔصٌادة انخشخٍج انضٕئً.

الملخص العربي
 .انظبغت انًخظظت
يعانضت انغطح انخاسصً:
 .انخهًٍع
 .انخضصٍش
 .انخهًٍع رى انخضصٍش
ٔرنك قبم عًهٍت انخعخٍق نهضسكٍَٕا ٔبعذْا
الوىاد واألساليب:
الوىاد: انضسكٍَٕا انًغخقشة بانٍخشٌٕو راث انكشٌغخاالث انًُظًت بخكُٕنٕصٍا انُإَ.
األساليب :
تذضير العيناث:
حى ححضٍش 3٠ عٍُت يٍ انضسكٍَٕا كايهت انكفاف ٔانخً قغًج ئنى يضًٕعخٍٍ سئٍغٍخٍٍ
بحغب طشٌقت انخهٌٍٕ كاَحً:
يضًٕعت ٢: ححٕي 0٠ عٍُت حهٌٕ بطشٌقت اإلغًاس فً انظبغت أحادٌت انهٌٕ.
يضًٕعت ٥: ححٕي 0٠ عٍُت حهٌٕ بٕاعطت انفششاة بطشٌقت انظبغ انًخظض.
حى حقغٍى كم يضًٕعت ئنى رالد يضًٕعاث فشعٍت بحغب يعانضت انغطح انخاسصً ئيا:
 .انخهًٍع فقظ
 .انخضصٍش فقظ
 .انخهًٍع رى انخضصٍش

هقذهت البذث:
حًخاص يادة انضسكٍَٕا دَٔا عٍ باقً انًٕاد انخضفٍت بخٕاص يٍكاٍَكٍت حضاًْ خٕاص
انًعادٌ ٔ نٌٕ يًٍض ًٌارم نٌٕ طبقت انعاس انطبٍعً نألعُاٌ. ٔنكٍ ٔحخى ٔقج قشٌب صذا نى
حُضح حكُٕنٕصٍاث انخظٍُع فً حضٍٓض يادة صسكٍَٕا ححًم خاطٍت انشبّ شفافٍت نخًارم حًايا
يظٓش األعُاٌ انطبٍعٍت يٍ حٍذ شبّ انشفافٍت، يٍ ُْا صاءث انحاصت ئنى انكغٕة انخضفٍت
ٔانخً كاَج حإدي ئنى بٍُت يخخهفت األطٕاس ضعٍفت ئنى حذ كبٍش.
ٔنًٕاصٓت ْزا انخحذي، كاَج انًحأالث إلٌضاد صسكٍَٕا بخاطٍت انشبّ شفافٍت حًكُُا
يٍ اعخبعاد انحاصت نهكغٕة انخضفٍت. يإخشا، طشحج صسكٍَٕا يبخكشة يغخخذيت حكُٕنٕصٍا انُإَ
نخحقٍق حهى حظٍُع حشيًٍاث صسكٍَٕت كايهت انكفاف ححًم يًٍضاث صًانٍت ٔيٍكاٍَكٍت يزانٍت.
ياصال انخغاؤل حٕل طشٌقت انخهٌٍٕ انًزهى نهخشي ًٍاث انضسكٍَٕت كايهت انكفاف ،
ٔانًعانضت األفضم نهغطح انخاسصً يحٕس نهبحذ خاطت يٍ حٍذ حأرٍشِ عهى انخظائض
انبظشٌت نهًادة عٕاء قبم أٔ بعذ انخعخٍق.
هذف البذث:
طًى ْزا انبحذ نذساعت:
 انقذسة عهى اعخُغاخ انهٌٕ
 خاطٍت انشبّ شفافٍت
 خاطٍت انبشٌق.
نهخشيًٍاث انضسكٍَٕت كايهت انكفاف باخخالف:
طشٌقت انخهٌٍٕ:
 انظبغت أحادٌت انهٌٕ.

لجنت اإلشراف

أ.م .د. / طارق صالح هرسى
أعخار يغاعذ بقغى انخٍضاٌ ٔانضغٕس
كهٍت طب األعُاٌ – صايعت عٍٍ شًظ

د. / عورواألتربي
يذسط بقغى انخٍضاٌ ٔانضغٕس
كهٍت طب األعُاٌ – صايعت عٍٍ شًظ

تأثير طريقت التلىين وهعالجت السطخ الخارجي على النتائج
الجواليت للترهيواث الزركىنيت كاهلت الكفاف

سعانت نهحظٕل عهى دسصت انذكخٕساة فى انخشكٍباث انزابخت
كهٍت طب انفى ٔاألعُاٌ، صايعت عٍٍ شًظ.

يقذيت يٍ انطبٍبت / سارة ههنى إبراهين صبيخ فىدة
بكانٕسٌٕط طب ٔصشاحت انفى ٔاألعُاٌ صايعت عٍٍ شًظ ٠٠٥2
ياصٍغخٍش انخٍضاٌ ٔانضغٕس، صايعت عٍٍ شًظ ٢٢٠٥
يذسط يغاعذانخشكٍباث انزابخت بقغى انخٍضاٌ ٔانضغٕس، كهٍت طب األعُاٌ ،
صايعت عٍٍ شًظ

صايعت عٍٍ شًظ
كهٍت طب األعُاٌ
٢٠٥2