Journal of Dental Medicine

Statement of Problem: Color matching and accurate shade selection are the challenging problems common to restorative dentistry. In ceramometal restorations, the type of substructure alloy affects the final color of bonded porcelain. Nickel- chromium alloy is the most commonly used one that its Iranian product, namely Minalux, is similar to Verabond2.
Purpose: The aim of this study was to assess and compare various color dimensions resulting from Minalux and Verabond2 alloys.
Materials and Methods: Nine disks, approximately 16 mm in diameter and 0.5 mm thickness, were cast from each alloy. Then, porcelain Vita VMK68 A2 was baked onto the entire test disks, following the manufacturer's instruction. Color samples, at the same time and under the same conditions, was measured by Data color spectrophotometer in CIE Lab System and Munsel system under four light sources (A, C, D65 and TL81). Then MATLAB TOOL BOX Statistic 5.2 was used to determine mean and bilateral variance analysis.

Results: It was indicated that the F value on hue, value and chroma was less than of the table value stated with 99% coefficient confidence, confirming Ho theory. In other words, there were not any significant differences between ceramometal disks made of Minalux and Verabond2 in the three dimensions of color.
Conclusion: Having desirable physical, mechanical and biological properties, Verabond2 can be replaced by Minalux alloy.

Background and Aim: With the introduction of porcelain veneers to fulfill patients’ esthetic needs, question raises about the ability of the veneers to cover the substructure discoloration. It seems that using shade modifiers under the porcelain veneers can neutralize the discoloration. The goal of this study was to determine the efficacy of shade modifiers in correcting tooth discoloration, when used with resin cements under porcelain veneers.

Materials and Methods: In this experimental study, 60 porcelain discs with two thicknesses of 0.7 mm and 2 mm (30 porcelain of each thickness) were made from ceramco porcelain powder. 40 of them were in A2 shade and 20 were made by the mixture of A2 shade porcelain powder and porcelain stain to represent tooth discoloration. Then all the laminate discs (0.7 mm) were cemented over the 2 mm thick discs to make groups of 10 samples as followed: 1- The first group: laminate discs + resin cement + 2mm thick discs with A2 shade. 2- The second group: laminate discs + resin cement + 2mm thick discolored discs. 3- The third group: laminate discs+ resin cement+ shade modifier+ 2mm thick discolored discs. The color of 30 specimens was measured by spectrophotometer in 2 conditions. 1- To include the specular reflection (SCI). 2- To exclude specular reflection (SCE). In each condition the specimens were measured on both a white background (W) and a black one (B). The mean color differences (E) of each specimen in the second and third group with the specimens of the first group were calculated. Data were analyzed using Paired sample t-test and P<0.05 of significance.

Results: Color measurements showed that in SCIW condition L was significantly different among the three groups except the first and the third. In SCEW condition all the parameters showed significant differences. In SCIB condition, E was not significantly different between the second and the third groups. Hue (h) parameter wasn’t different between groups one and three neither was chroma (c) among the three groups. In SCEB condition, E was not statistically different between groups two and three.

Conclusion: Considering the statistical results, shade modifier couldn’t completely match the color of the specimens in the third group with the first one. But, the lower E for the third group comparing to the second one means that shade modifier was successful in reducing the effect of substructure discoloration.