Threshold contrast ratio and masking ability of porcelain veneers with high-density alumina cores.

Purpose: The purposes of this study were to: (1) investigate the correlation between the color difference of bilayer porcelain veneers over white and black backgrounds (deltaE1) and their opacity (contrast ratios); (2) determine whether there is a recommendable threshold contrast ratio above which the color difference is clinically acceptable (when deltaE < or = 5); and (3) compare the ability of porcelain veneers to mask a color change from white to black backgrounds (deltaE1) and their ability to mask a color change from white to clinically discolored teeth (deltaE2).

Materials And Methods: Forty-four maxillary anterior teeth of eight patients with severe tetracycline discoloration were prepared for bilayer porcelain veneers in shade A2 porcelain. The cores were 0.25 mm thick. The color (CIE L*a*b*) and reflectance (Y) of the midbuccal region of each veneer were measured over white and black backgrounds using a colorimeter under artificial daylight. The veneers were bonded to discolored teeth, and their color was measured after 1 week.

Results: The mean color difference deltaE1 was 10.6 (SD 2.6). The mean contrast ratio was 0.75 (SD 0.1). There was a close and statistically significant correlation between deltaE1 and contrast ratio. The determined threshold contrast ratio was 0.91. The mean color difference deltaE2 was 11.6 (SD 5.5). A paired t test showed no difference between deltaE1 and deltaE2.

Conclusion: There was a significant correlation between the masking ability of veneers (deltaE1) and their opacity (contrast ratio). There was no significant difference in the ability of the porcelain veneers in masking a color change from white to black backgrounds compared to their ability to mask the color change from white to the discolored teeth.