Effectiveness of interceptive orthodontic treatment in reducing malocclusions Gregory J. Kingaand Pongsri Brudvikb Seattle, Wash, and Bergen, Norway… [602350]

ORIGINAL ARTICLE
Effectiveness of interceptive orthodontic
treatment in reducing malocclusions
Gregory J. Kingaand Pongsri Brudvikb
Seattle, Wash, and Bergen, Norway
Introduction: In this retrospective cohort study of the effectiveness of interceptive orthodontic treatment, we
compared patients receiving interceptive orthodontic treatment with untreated control subjects. Methods:
Models were scored by using the index of complexity, outcome and need (ICON). Control models (n 5113)
were archival and were selected based on malocclusion in the early mixed dentition and no orthodontic treat-
ment during the subsequent 2 years. The patients (n 5133) were in the mixed dentition and consecutively
treated in the University of Bergen orthodontic clinic. Initial ages were 9.4 years (6 1.4) for the treated group
and 9.3 years ( 60.8) for the control group. The treatment took a mean of 27.2 months (6 16.3) for the patients;
the control group was observed for a mean of 24.4 months (6 3.6). Subject Groups were matched for age,
need, complexity, duration, and all ICON components except spacing (P \0.006) and crossbite (P \0.000).
Results: ICON scores decreased after treatment by 38.8% (P \0.0001) from 54.9 (6 16.6) to 33.6 ( 616.1).
The controls were unchanged, with ICON scores of 54.0 (6 14.8) and 54.2 (6 16.9). Improvement grades
were different ( P\0.0001), with most controls categorized as ‘‘not improved or worse’’ (89.4%), whereas
only 36.1% of the treated group were in that category. However, there were increases in the ‘‘minimal,’’ ‘‘mod-
erate,’’ and ‘‘substantial’’ improvement categories for the treated subjects (22.6%, 21.1%, and 17.3%, re-
spectively). The controls did not change in any ICON component and worsened in crowding (P \0.007),
whereas the patients improved in esthetics, crowding, crossbite, and overbite (P \0.007). Conclusions:
These results indicate that interceptive orthodontic treatment is effective for improving malocclusion butdoes not produce finished-quality results. (Am J Orthod Dentofacial Orthop 2010;137:18-25)
Interceptive and preventive orthodontic procedures
are relatively simple and inexpensive treatment ap-
proaches that target developing malocclusions dur-
ing the mixed dentition. Orthodontists perceive these asuseful ways to reduce the severity of malocclusions,
1
improve a patient’s self-image, eliminate destructivehabits, facilitate normal tooth eruption, and improvesome growth patterns.
2Because of this, some have ad-
vocated their wider use as public health measures aimed
at reducing the burden of malocclusion in underserved
populations3and as a strategy for increasing access to
orthodontic treatment when resources are limited.1
Available evidence suggests that patients at risk for
severe malocclusion can readily be identified in themixed dentition, and that the burden of these malocclu-
sions in this age group is substantial (about 25%-30%).
In 1 study, patients at risk for future orthodontic prob-lems were identified in 28% of those examined, andmost of the developing malocclusions were judged tobe suitable for interceptive orthodontic treatment.
4A
similar study found that about 27% of the children ex-amined in a large Nigerian sample needed some formof interceptive orthodontic treatment.
3A third study
of children screened in a community dental clinic atages 9 and 11 years also found that one-third wouldbenefit from interceptive orthodontic treatment.
5
Although interceptive orthodontic procedures often
do not produce finished orthodontic results withouta second phase of treatment in the permanent dentition,several studies have suggested that systematicallyplanned interceptive treatment in the mixed dentition
might contribute to a significant reduction in treatment
need between the ages of 8 and 12 years, often produc-ing results so that further need can be categorized aselective. In a Finnish study, the need was reduced signif-icantly from ages 8 to 12 in a small group receiving in-terceptive treatment.
6In a similar study, 94% of the
children receiving interceptive treatment in a commu-nity health clinic were judged to have completely suc-
cessful results, with only 2% showing deterioration.
5aMoore Reidel Professor, Department of Orthodontics, University of
Washington, Seattle.
bAssociate professor, Department of Orthodontics, University of Bergen,
Bergen, Norway.
Supported by NIDCR grant U54 DE14254.The authors report no commercial, proprietary, or financial interest in theproducts or companies described in this article.Reprint requests to: Gregory J. King, University of Washington, Department ofOrthodontics, Box 357446, Seattle, WA 98195; e-mail, gking@u.washington.
edu.
Submitted, December 2007; revised and accepted, February 2008.0889-5406/$36.00Copyright /C2112010 by the American Association of Orthodontists.
doi:10.1016/j.ajodo.2008.02.023
18

Using the peer assessment rating (PAR)7and the index
of complexity, outcome and need (ICON),8the authors
of another study reported significant reductions in mal-
occlusion severity after early treatment in both Medic-
aid and privately financed patients, with comparable
results in both groups.9In addition, about two thirds
of those patients changed from a ‘‘medically necessary’’category, as judged by the handicapping labiolingualdeviation index
10to ‘‘elective’ ’ after mixed dentition
orthodontic intervention.11
Although the available data suggest that interceptive
orthodontic treatment can be effective, no randomized
clinical trials or large cohort studies have compared in-
terceptive outcomes with no treatment in either the nearor long term. This has been primarily due to the lack ofsuitable cohorts of untreated patients with malocclu-sions to serve as control subjects. During the 1970s,the orthodontic faculty at the University of Bergen inNorway collected orthodontic study casts biannuallyfrom many local school children. A substantial number
of these children had orthodontic needs and were not
treated during the mixed dentition. Thus, it was possibleto collect an archival cohort of study casts of untreatedsubjects with excellent matching for malocclusionseverity to compare with a contemporary sample of pa-tients treated in an interceptive clinic. We hypothesizedthat interceptive orthodontic treatment would improvemalocclusions with reductions in their complexity and
need.
MATERIAL AND METHODS
This was a retrospective cohort design. Power calcu-
lations were based on a similar study with a 40% im-
provement in ICON scores after interceptivetreatment.
9A sample size of 100 provided a power of
90% and an alpha of 0.05 for this level of differencein ICON scores. For the treated group, 133 patientswith pre- and postinterceptive sets of dental casts wereselected from consecutively treated patients who metour inclusion criteria and were treated in the orthodonticclinic at the University of Bergen by dental students su-pervised by orthodontic faculty members. Most of thesepatients were treated for dental misalignment, crowding
or spacing, inversions, anterior open bite, and crossbite
with various removable appliances. The control group,consisting of 113 patients with 2 sets of dental caststhat also met the inclusion criteria, was randomly se-lected from departmental archives of biannual recordsof school children taken during the 1970s. Inclusionand exclusion criteria were initial casts in the earlymixed dentition, final casts after interceptive orthodon-
tic treatment but no later than the late mixed dentition(ie, final casts with a fully erupted permanent dentition
mesial to the first molars were excluded), final casts forthe control group who received no orthodontic treat-ment were taken 2 years after the first, initial casts show-
ing a malocclusion suitable for funding under the
Norwegian Social Security System as judged subjec-tively by an orthodontist (P.B.) experienced with thesecriteria, Scandinavian ethnicity, and no exclusion basedon sex.
All casts were scored with the ICON by a calibrated
examiner (G.J.K.) who was not blinded to group or timepoint. True blinding was not possible because the casts
of the control group were easily recognizable because of
their rough trimming, and the time points were obviousbased on the stage of tooth development evident on thecasts. The ICON scores overall occlusion and an es-thetic component of malocclusion on an interval scale,from 0 to 120 for the former and 0 to 10 for the latter.The higher the ICON score, the worse the malocclusion.The ICON has been validated based on the subjective
judgments of 97 orthodontists from 9 countries on 240
initial and 98 treated dental casts. Created as a singlemeasure of need, complexity, and outcome simulta-neously, the ICON has 2 advantages over the more com-monly used PAR as a dental outcome measure.
7,12It has
an esthetic component that is weighted highly by clini-cians and valued by patients, and it has clear and inter-nationally validated cut points for treatment need and
outcome with categories for complexity and improve-
ment. Five weighted parameters are scored and com-prise the components of the ICON: dental esthetics,crossbite, anterior vertical relationship, maxillarycrowding or spacing, and buccal segment anteroposte-rior relationship. The components were individuallyscored from dental casts and multiplied by their respec-tive weights to yield a single summary ICON score. This
final score was then used to determine initial need
(ICON .43) and final outcome acceptability (ICON
\31), and difference scores were used to determine im-
provement. According to the convention recommendedby the developers of the ICON, improvement scoreswere calculated by subtracting 4 3final scores from
the initial scores.
8This permitted us to compare the im-
provement in our samples with the categories validated
for the ICON. Intrarater reliability of the examiner was
determined by using Dahlberg’s formula13on 10 sets of
models remeasured 2 weeks apart and was considered tobe acceptable (4.1 ICON points).
Initial equivalence of the groups was assessed by us-
ing age, sex, and malocclusion characteristics. The lat-ter consisted of weighted initial ICON scores andunweighted ICON component scores. Equivalence in
ICON components was assessed by using multipleAmerican Journal of Orthodontics and Dentofacial Orthopedics King and Brudvik 19
Volume 137, Number 1

unpaired ttests with Bonferroni adjustments for multi-
ple comparisons. Since 7 tests were performed, the level
of significance was set at P\0.007 (ie, P\0.05/7).
ICON scores were compared between groups and atthe 2 time points with 2-way analysis of variance (AN-OV A) and post-hoc comparisons with the Kruskal-Wallis test if P\0.05. Initial need was determined by
using the weighted ICON score threshold of .43, and
end-of-study acceptability was determined with the
\31 threshold. The prevalences of subjects in the initial
complexity grades and improvement categories werealso calculated, and these distributions were comparedbetween groups by using the chi-square statistic. Un-weighted ICON component scores were compared be-tween initial and final casts, and differences were
assessed with multiple ttests with Bonferroni adjust-
ments and significance set at P\0.007.
RESULTS
Initially, the subjects in the interceptive and control
groups had mean chronological ages of 9.4 years ( 6
1.4) and 9.3 years ( 60.8), respectively ( Table I ). These
were not different. However, although the treated group
was about equally divided by sex (51.6% female), thecontrol group was predominantly male (31.8% female).These were statistically different ( P50.017). As as-
sessed by the unweighted ICON component scores,the malocclusions in the 2 groups were largely wellmatched, with moderate esthetics scores, minimal max-
illary crowding or spacing and openbite or overbite, and
moderate buccal anteroposterior occlusal relationships.Statistical differences were found only in maxillary an-terior spacing ( P\0.006) and crossbite ( P\0.000).
Table II shows that both groups had similar ICON
scores when the first models were taken (54.9 and54.0, respectively). Based on the validated ICON as-sessment of need ( .43), both groups of subjects needed
treatment. The intervals between the first and secondsets of casts averaged 27.2 months ( 616.3) in the
treated group and 24.4 months ( 63.6) in the control;
these were not different. At the second time point, the
mean ICON scores were 33.6 ( 616.1) for the treated
group and 54.2 ( 616.9) for the untreated controls.
This represented a 38.8% improvement for the former
(P\0.0001) and no change for the latter. Based on
the ICON acceptability cut point of \31, both groups
would be judged unacceptable, but the treated cohortwas borderline.
The distributions of the initial complexity grades
(Fig 1 ) were not different between the groups (chi-
square: P50.186). Figure 2 gives a comparison of
the distributions of improvement grades between the 2groups. The difference between these was highly signif-icant (chi-square, P\0.0001). Whereas most subjects
were categorized as ‘‘not improved or worse’’ in the un-treated control group (89.4%), the treated group had36.1% in that category. This reduction was reflected
by roughly equivalent increases in the ‘‘minimal,’’
‘‘moderate,’’ and ‘‘substantial’’ improvement categoriesfor the treated subjects (22.6%, 21.1%, and 17.3%, re-spectively) compared with the controls (7.9%, 1.8%,and 0.9%, respectively).
Improvements in the various ICON categories are
shown in Figures 3 and 4 . The untreated controls had
no improvement in any component and a statistically
significant worsening of maxillary crowding ( P5
0.007). In contrast, the treated sample showed statisti-
cally highly significant improvements in the estheticand crossbite components ( P\0.0001), with significant
improvements in the maxillary-crowding and open-bitecomponents (0.001 \P\0.007).
DISCUSSION
This study supports the hypothesis that a systematic
program of interceptive orthodontic treatment duringthe mixed dentition is more effective than doing nothingto improve malocclusions over the near term. Thisfinding supports other studies that have reported similar
improvements but has the added advantage of includingTable I. Initial comparison of groups
lnterceptive Control Pvalue
Age (y) (SD) 9.4 (1.4) 9.3(0.8) 0.590
Female (%) 51.6 31.8 0.017
Mean ICON (SD) unweighted components
Esthetics (1-10) 5.3(1.8) 5.2 (1.7) 0.469
Crowding (0-5) 0.6 (1.3) 0.4 (1.6) 0.414
Spacing (0-5) 0.2 (0.5) 0.4 (0.7) 0.006
Crossbite (0-1) 0.6 (0.5) 0.2 (0.4) 0.000Open bite (0-4) 0.3 (1.0) 0.2 (0.6) 0.277
Overbite (0-3) 0.6 (0.8) 1.0 (0.9) 0.008
Buccal AP (0-2) 1.1 (0.8) 1.2 (0.5) 0.500
AP, Anteroposterior relationshipTable II. Changes in ICON scores by group
lnterceptive
(n5133)Control
(n5113)ICON cut points
(need or acceptability)
Initial mean ICON
(SD)54.9 (16.6) 54.0 (14.8) .43
Final mean ICON
(SD)33.6 (16.1) *54.2 (16.9) \31
lmprovement % 38.8 /C00.9
*P\0.0001 (initial vs final; interceptive vs control).20 King and Brudvik American Journal of Orthodontics and Dentofacial Orthopedics
January 2010

an untreated cohort with similar initial malocclusions to
address spontaneous improvement or worsening duringthe transition from the deciduous to the permanent den-tition.
5,6,9,11The untreated control group in this study
showed little change in overall ICON scores with
most subjects in the ICON ‘‘not improved or worse’’category. This finding clearly supports the conclusion
that these malocclusions do not change in any signifi-cant ways during the mixed dentition without interven-tion. Conversely, the treated group had far fewerpatients in this ‘‘not improved or worse’’ category but
increases in the ‘‘minimal,’’ ‘‘moderate,’’ and
Fig 1. Percent of subjects in the ICON initial complexity categories: easy, \29; mild, 29-50; moder-
ate, 51-63; difficult, 64-77; very difficult, .77. Interceptive and control distributions were not different
based on the chi-square statistic.
Fig 2. Percent of subjects in the ICON improvement categories: improvement scores 5initial ICON
score – 4 x final ICON score. Greatly improved, .–1; substantially improved, –25 to –1; moderately
improved, –53 to –26; minimally improved, –85 to –54; not improved or worse, \–85. Based on the
chi-square statistic, the interceptive and control distributions were highly significantly different
(P\0.0001).American Journal of Orthodontics and Dentofacial Orthopedics King and Brudvik 21
Volume 137, Number 1

‘‘substantial’’ improvement categories, suggesting that
interceptive treatment improves malocclusions to vary-ing degrees. However, few patients in either group were
in the ‘‘greatly improved’’ category, supporting the hy-pothesis that interceptive orthodontic treatments often
require further treatment in the permanent dentition.
When we considered the various components of
malocclusion, the untreated group experienced no
Fig 3. Changes in ICON components in the untreated control group (unweighted). The initial scores
were statistically different from the final scores based on the ttest (*P\0.007).
Fig 4. Changes in ICON components in the interceptive treatment group (unweighted). The pretreat-
ment scores were statistically different from the posttreatment scores based on the ttest (*0.001 \
P\0.007; **P \0.0001).22 King and Brudvik American Journal of Orthodontics and Dentofacial Orthopedics
January 2010

improvement in any category and a statistically signifi-
cant worsening of maxillary crowding, whereas thetreated group had improvements in esthetics, crossbite,maxillary crowding, and anterior open bite. The deteri-
oration in maxillary crowding in the untreated sample
during the mixed dentition might have been caused bya loss of arch perimeter caused by caries, since thisarchival sample subjectively appeared to have moreinterproximal caries, restorations, and early loss ofdeciduous teeth than did the more contemporary treatedsample. This suggestion is supported by Norwegianstudies reporting declines in caries incidence during
the interval covered by the 2 groups in this study,
14,15
with the extensive use of fluoride-based preventive
programs cited as the major factor contributing to thedecline during the late 1960s and early 1970s.
16
This comparison did not consider the long-term sta-
bility of interceptive orthodontic corrections. Withoutsuch a comparison, it is impossible to know the extentto which these partial corrections have any lasting ben-
efit, or how they compare over the long term with com-
prehensive treatment. Preferably, a randomizedcontrolled trial designed to compare interceptive withcomprehensive treatment over the long term would berequired, but such a study has not yet been reported.Randomized controlled trials designed to examine1-phase vs 2-phase treatment of Class II malocclusionsindicate that early intervention has a short-term benefit
over no treatment but offers no advantage over 1-phase
treatment at adolescence.
17,18However, these studies
did not have groups receiving only phase-1 treatment,so they could not address the long-term stability of earlytreatment alone. Because interceptive orthodontic treat-ment has limited goals aimed at reducing, rather thaneliminating, features of malocclusion, it is consideredto be partial treatment by most orthodontists; our data
support that conclusion. If producing an ideal occlusion
lessens the risk of relapse as some contend, one mightpredict that comprehensive treatment would havegreater stability. However, the question of how the qual-ity of outcome influences posttreatment stability is de-batable, with some evidence suggesting that, over thelong term, excellent results tend to deteriorate, whereasaverage results tend to improve.
19
The comparison groups were well matched with re-
spect to the main outcomes for testing the hypothesis:age, need, complexity, and treatment duration. How-ever, there were some lack of comparability in less rel-evant features that might reflect clinician and patientbiases in favor of early treatment for some populationsubgroups and malocclusions as well as differences indental health between the years covered by the 2 groups.
Comparison of initial complexity data suggests slightlymore mild-to-moderate malocclusions in the control
group and more difficult-to-very-difficult cases in thetreated group. This seems reasonable, since one expectsthat there would be parental pressure to begin treatment
early for children with more significant impairments.
20
Since mixed dentition treatment was an exclusion crite-
rion for the control group in this study, some subjectswith the most severe problems requiring early treatmentmight have been excluded from the control sample. Thisalso might explain the curious finding of more boys inthe control sample, since demand for orthodontic treat-ment is known to be higher for girls.
21
Matching also was generally good with respect to
the various components of malocclusion with differ-ences only in more maxillary spacing and fewer cross-bites in the controls. Many clinicians, including theorthodontic faculty at the University of Bergen, treatcrossbites during the mixed dentition because youngerpatients are thought to respond better to treatment; earlytreatment also prevents the risk of asymmetric facial
growth and gingival damage.
22-24Despite recent reports
that do not strongly support many of these beliefs, this
practice is common worldwide.25,26This could explain
why these patients were found less frequently in our un-treated sample. A greater amount of initial maxillaryspacing in the untreated sample might reflect greaterincisor flaring in this group. The tendency for higheroverbite scores in this group further supports this inter-
pretation. Despite good matching on several important
criteria for testing the main hypothesis, the failure toachieve perfect matching in all categories examined isa limitation of this study, since some of these mightbe confounders in data interpretation.
The wider use of interceptive orthodontic treatment
has been proposed as a public health measure for reduc-ing the burden of malocclusions in developing coun-
tries
3and for increasing access to orthodontic services
for underserved populations (low-income, ethnic minor-
ities, and geographically isolated subgroups).1The
rationale for this derives from the hypothesis that ortho-dontists can more readily provide shorter, simpler inter-ceptive and preventive treatments to low-incomefamilies compared with the alternative of more expen-sive and longer comprehensive treatments. Cost-effec-
tiveness analyses are necessary to demonstrate the
economic value of this strategy compared with compre-hensive treatment in the permanent dentition. A Finnishstudy found that the cost was lower in 1-stage treatmentsstarted in the permanent dentition compared with2-stage treatments started in the mixed dentition.
27
However, no studies have compared mixed dentition in-terceptive treatment alone vs comprehensive permanent
dentition treatment alone. Nevertheless, data fromAmerican Journal of Orthodontics and Dentofacial Orthopedics King and Brudvik 23
Volume 137, Number 1

a decision analysis designed to evaluate potential sav-
ings by reducing the proportion of children offeredfree orthodontic treatment through the National HealthService in Denmark suggest that this reduction actually
results in increased consumption of resources overall.
28
This finding lends support to the idea that a comprehen-
sive strategy designed to increase access to interceptiveorthodontic services might be more cost-effective over-all than the competing one of focusing primarily on com-prehensive treatment in the permanent dentition for themost difficult malocclusions.
The use of the ICON as the measure of the effective-
ness of interceptive orthodontic treatment ignores possi-ble psychological and quality-of-life benefits that can bederived from these approaches. These factors are oftencited as justifications for orthodontic treatment. Thisstudy supported the effectiveness of interceptive treat-ments at improving esthetics but did not address qualityof life. According to several reports in the literature, thedecision to seek orthodontic care is based on the desire
to improve dental esthetics, self-esteem, and social ac-
ceptance, not necessarily on the degree of malocclusionseverity.
29,30In a study evaluating the psychosocial ef-
fects of early treatment, self-concept improved, andnegative social experiences declined, suggesting thatimproved self-esteem might be an important benefit ofinterceptive orthodontic treatment.
31
The unweighted ICON component data seem to sug-
gest that some types of interceptive treatments are moreeffective than others. This is lost in the summary ICONdata, when the weightings are applied, and the contribu-tions from the individual components are masked. In theICON validation, certain component scores (eg, es-thetics) were weighted much more highly by the expertsthan others. Therefore, these components tend to drivethe summary results. Also, the ICON scores compo-
nents of malocclusion, not the effectiveness of certain
treatment approaches. For the latter, it would be moreappropriate to actually measure the various features ofmalocclusion that are addressed by certain types of in-terceptive treatment (eg, overjet by headgear).
CONCLUSIONS
1. Interceptive orthodontic treatment initially im-
proves malocclusions with reductions in complex-ity and need compared with doing nothing.
2. Interceptive orthodontic treatment often requires
follow-up treatment in the permanent dentition.
We thank Kirsten Thunold for collecting the study
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