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


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.


CONCLUSIONS
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.
Faculty of Dentistry, The University of Hong Kong, China. cschu@hkucc.hku.hk
Frederick C S
FC
Chu
Arthur S K
AS
Sham
Henry W K
HW
Luk
Bernt
B
Andersson
John
J
Chai
Tak W
TW
Chow
D000537:Aluminum Oxide / Q000737:chemistry*; D003116:Color; D003118:Color Perception; D003124:Colorimetry; D003776:Dental Porcelain / Q000737:chemistry*; D003801:Dental Veneers; D004056:Differential Threshold; D006801:Humans; D016555:Matched-Pair Analysis; D008422:Materials Testing; D055095:Optics and Photonics; D011176:Post and Core Technique / Q000295:instrumentation; D013997:Time Factors; D014075:Tooth Discoloration / Q000503:physiopathology / Q000628:therapy
D003776:Dental Porcelain; D000537:Aluminum Oxide