Considerations regarding the influence of layering thickness on the esthetics of a metal ceramic restoration Rîcă R.1,a, Rîcă Ana-Maria2,b, Manolea… [600816]

Considerations regarding the influence of layering thickness on the esthetics of a metal ceramic restoration Rîcă R.1,a, Rîcă Ana-Maria2,b, Manolea H.3,c, Opri Mirela4,d, Dodocioiu M.4,e 1Department of Dental Materials, Faculty of Dentistry, UMF Craiova, 2-4 Petru Rares Street, Craiova, Romania 2Department of Periodontology, Faculty of Dentistry, UMF Craiova, 66 1 Mai Blvd., Craiova, Romania 3 Department of Dental Materials, Faculty of Dentistry, UMF Craiova, 2-4 Petru Rares Street, Craiova, Romania 4Department of Dental Prosthesis Technology, Faculty of Dentistry, UMF Craiova, 2-4 Petru Rares Street, Craiova, Romania [anonimizat], [anonimizat], [anonimizat], [anonimizat], [anonimizat] Keywords: dental ceramics, porcelain, layer thickness, shade, esthetic restoration
 
 
 
 
 
 
 
 Introduction Currently, the options for prosthetic rehabilitation have increased significantly with the popularization of metal-free prosthesis or the rank of osseointegrated implants, presenting satisfactory results concerning esthetics or function. However, the conventional metal-ceramic fixed partial dentures are still of great importance in the dental clinic because of their versatility, being viable where other therapeutical modalities are not, as well as for its accessible cost. (Pretti 2004) Aim of the study The aim of the study was to evaluate the influence of each layer of porcelain fused to the metal coping on the final aspect of a metal ceramic restoration using the Ivoclar dSign system. Material and method In our study we have have compared three metal-ceramic anterior restorations from an esthetically point of view. As there are many porcelain systems and techniques currently available for utilization in full-coverage anterior crowns restorations, we have chosen to use a simple buildup technique for the restorations and the Ivoclar dSign system for our esthetic comparison. Results We have used a gypsum model with a preparation on the 2.1 central incisor in order to obtain a metal-ceramic restoration using a simple ceramic build-up on the metal copings. The model was cast using type IV gypsum produced by Surface and we used a die system from Bredent. The wax-up of the metal coping was made using the immersion method employing a special memory wax from Bredent.

The investment was completed in two steps. The first step was to apply a liquid investment material on the external and internal surfaces of the wax-pattern of the metal copings prepared for investing. The second step was to complete the procedure by adding a classic investment material from Bego. After the preheating and the heating of the invested pattern, the molten alloy (Niadur) was cast into the mold by using a low-frequency induction casting machine – Ducatron Serie 3. After the de-investing procedure, the metal framework was adapted on the model and sandblasted. Prior to the application of the opaque, the metal frame was submitted to an oxidation firing in the porcelain furnace. The oxide layer was then sandblasted with aluminum oxide. Two layers of opaque were applied on the metallic structures. The first layer of base dental porcelain was applied on the restoration. The build-up continued with layers of dentin and after the firing the enamel layer was finally applied. After the application of the enamel layer we have once again fired and afterwards we have completed the glazing and the finishing of the dental porcelain. The three metal-ceramic restorations were subjectively examined in both artificial and natural lighting conditions. The photographs taken are revelatory for the esthetic properties of each restoration. The thickness of the various layers and the desired shade are to be correlated with the total thickness of the ceramic veneer and this is essential in order to obtain a high quality esthetic restoration. (Corciolani 2010) Conclusion For a highly esthetic result the thickness of the various layers of dental ceramics must be correlated with the shade that we want to obtain. The layer thickness of the opaque porcelain, the body porcelain (dentin), and the incisal porcelain greatly influence the final aspect of the metal ceramic restoration and this variation must be taken into consideration in order for the dental technician to obtain the desired shade. References Pretti Mariana, Holgert E., Bottino M.A., Avelar R.P. Evaluation of the shear bond strength of the union between two CoCr-alloys and a dental ceramic. J. Appl. Oral Sci. Vol.12, No.4 Bauru Oct./Dec. 2004 Corciolani G., Vichi A., Louca C., Ferrari M. Influence of layering thickness on the color parameters of a ceramic system. Dent Mater 2010 Aug; 26(8): 737-42. Fig. 1. Obtaining the gypsum model Fig. 2. Obtaining the wax pattern for the metal copings using the dipping technique Fig. 3. The wax pattern for the metal copings Fig. 4. Spruing the wax pattern Fig. 5. Application of the liquid investment material. Fig. 6. Obtaining the mold cavity Fig. 7. Casting the alloy Fig. 8. The removal of the investment material off the surface of the alloy Fig. 9. Finishing the metal copings Fig. 10. The aspect of the metal copings after the oxidation firing Fig. 11. The application of the opaque on all the metal copings

Fig. 12. The application of the base dentin layer Fig. 13. The application of the dentin layer Fig. 14. The metal-ceramic restorations after the dentin layer firing Fig. 15. The application of the enamel layer Fig. 16. The metal-ceramic restorations before the enamel layer firing Fig. 17. Glazing and finishing the dental porcelain Fig. 18. The 3 metal-ceramic restorations – artificial lighting Fig. 19. The 3 metal-ceramic restorations – natural lighting Fig. 20. The metal-ceramic restoration with the thickest dentin layer build-up Fig. 21. The metal-ceramic restoration with an uniform ceramic build-up Fig. 22. The metal-ceramic restoration with the thinnest dentin layer build-up Fig. 23. The 3 metal-ceramic resorations with variable ceramic layer build-up