Influence of the background color and thickness of zirconia reinforced glass ceramics on the optical properties compared to lithium disilicate glass ceramics

Statement of problem. Optical properties of contemporary all ceramic restorations are influenced by background color and thickness has dearth of information.Purpose. The purpose of this study was to evaluate the influence of the background color and thickness of zirconia reinforced glass ceramics on the optical properties compared to lithium disilicate glass ceramic.Materials and methods. Fifty six ceramics rectangular plates were made from zirconia reinforced glass ceramic and lithium disilicate glass ceramic plates (n=28). The dimensions of the plates were (14 x 12 mm). The plates of each group were divided into two subgroups of two different thicknesses 1.0, 1.5 mm (n=14). Again, specimens were divided into two divisions according to composite background shade into division (A2 and C3). The ceramic plates of each materials and thicknesses were optically connected with drop of distilled water to either two composite background shades. The color change ΔE between ceramic-composite assembly and ceramic plates was measured for all tested group. The data were analyzed with 3-way ANOVA followed by Bonferroni’s post-hoc test (α= 0.05). Results. ANOVA revealed that background color, ceramic type and thickness had a statistically significant effect on mean ΔL (p<0.05). The interaction between the three variables was not statistically significant (p=0.968). Conclusion. Zirconia reinforced lithium silicate ceramics could decrease the effect of color change of dark background more significantly than lithium disilicate glass ceramic.