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.
Chu
Frederick C S
FC
Faculty of Dentistry, The University of Hong Kong, China. cschu@hkucc.hku.hk
Sham
Arthur S K
AS
Luk
Henry W K
HW
Andersson
Bernt
B
Chai
John
J
Chow
Tak W
TW
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