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Volume 17 , Issue 1
January/February 2004

Pages 2428

Threshold Contrast Ratio and Masking Ability of Porcelain Veneers with High-Density Alumina Cores

Frederick C. S. Chu, BDS(Hons), MSc, FRACDS, MRDRCS/Arthur S. K. Sham, BSc, MSc/Henry W. K. Luk, PhD/Bernt Andersson, LDS, Odont Dr/PhD/John Chai, BDS, MS, MJ, DLaw/Tak W. Chow, BDS, MSc, PhD, FRACDS, FDSRCS, DRDRCS

PMID: 15008228

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 (E1) and their opacity (contrast ratios); (2)determine whether there is a recommendable threshold contrast ratio above which the color difference is clinically acceptable (when E  5); and (3)compare the ability of porcelain veneers to mask a color change from white to black backgrounds (E1) and their ability to mask a color change from white to clinically discolored teeth (E2). 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 E1 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 E1 and contrast ratio. The determined threshold contrast ratio was 0.91. The mean color difference E2 was 11.6 (SD 5.5). A paired ttest showed no difference between E1 and E2. Conclusion: There was a significant correlation between the masking ability of veneers (E1) 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. Int J Prosthodont 2004;17:2428.

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