Alma Ðozić, DDS, PhD

Original poster: Influence of Ceramic Layering on Color of CICERO CAD/CAM Restorations A. ÐOZIC*, E. BÜCHLER, M.P. AARNTS, J.M. VAN DER ZEL, M.C.A. MEEGDES, J. LAHDO A.J. FEILZER 

INTRODUCTION

It has been stated that the thickness of the enamel and the color of the underlying dentin can strongly influence the color of a tooth. This knowledge is applied in restorative dentistry when making metal-porcelain restorations with a layered structure. An experienced dental technician can achieve a natural tooth appearance by building up porcelain layers over the metal substructure. However skillful management of the relationships between the translucency and thickness of the outer and the inner layers is necessary to obtain an esthetically acceptable result.
Most all-ceramic CAD/CAM restorative systems produce monochromatic results, which are cosmetically less satisfying than the appearance of metal-porcelain restorations or manually made all-ceramic restorations with a layered built up. 
In order to make the all-ceramic layered CAD/CAM crown, CICERO dental industries b.v. has developed a sophisticated layering technique for their CAD/CAM system. It was hypothesized that esthetic effects such as natural translucency and color depth can be obtained with only Opaque Porcelain (OP) and Body Porcelain (BP) using a controlled (CAD/CAM) layering procedure.

AIM

The aim of this study was to investigate, whether thickness and color intensity of ceramic layers (Sintagon® ELEPHANT Dental) can influence the final color of CAD/CAM restorations.

MATERIALS AND METHODS

In this study a spectrophotometer procedure was used to determine color. The color was expressed by their L* a* b* values. A black or white background was chosen.
As we planned to determine the influence of disk combinations on disks that were not sintered together we first evaluate the test method by comparing the color of sintered layerd disks with that of assembled separate disks. A referential three-layered ceramic specimen was made in the laboratory according to the approximate thickness of the CICERO CAD/CAM restoration. The three layers (Synthoceram 0,7 mm + Sintagon Opaque Porcelain 0,5 mm + Sintagon Body Porcelain 0,5 mm in color A3) were pressed and fired together. Three loose disks of the same thickness and color were assembled upon each other with distillate water in-between as a light-conducting medium. 

Finally 5 combinations of assembled discs (see Table) were tested.

RESULTS

Between the sintered and the assembled specimen there was no significant difference in the L*, a*, or b* values, as measured with spectrophotometer.
The results (see table) of this study indicate that both OP/ BP layer thickness and the color intensity have a significant influence on L* a* b* values: 1) for the color A2 and A3, lightness (L*) increases as the thickness of OP decreases, whereas for the color A1 and B2, lightness (L*) tends to decrease as the thickness of OP decreases up to 0,5 mm; it then remains stable for color A2 and increases again for color B2. 2) Position in the color space (a* b*) for the samples with increased thickness of OP shifts significantly towards red (a*) and yellow (b*) for all 4 colors. 3) The background tone still has a small influence on overall color of the samples with 0,7 mm thickness of Synthoceram, whereby the samples with a white background have higher L* a* b* values in all measurements.

CONCLUSION

The change of OP and BP thickness and color intensity of the ceramic samples can significantly influence the color as expressed in L* a* b* values. The final colorimetric appearance of tooth restorations can therefore be predicted by setting the ceramic layer thickness and color intensity.

DISCUSSION

It is advisable to make use of all features of CAD/CAM technology by aiming for more-layered restorations, which correspond to the dentine and enamel layers of the natural tooth. CICERO Dental Industries b.v has proved to be able to manufacture two or three ceramic layers using CAD/CAM technique. 
The results obtained in this study will be used to build the layer-combination database that can serve as a color guide for the layered CAD/CAM crown production.

Email: a.dozic@acta.nl