RESUMO
This in vitro study evaluated the effects of preheating, ultrasound application, and composite resin luting agent composition on the optical characteristics of feldspar ceramic laminates. The hypothesis was that the optical properties of the ceramic-luting agent-substrate unit would be affected by the composition of the luting material and use of ultrasound. Preheated restorative composite resins Charisma, IPS Empress Direct, and Filtek Z350 were used, with unheated RelyX Veneer resin cement serving as the control. The response variables for the physical properties of the materials were degree of conversion (n = 3 per material) and viscosity (n = 3 per material). Seven groups were generated based on the tested luting agent and the use of ultrasound. Color parameters were evaluated with a spectrophotometer at 3 timepoints (before luting [baseline], 24 hours after luting, and 1 month after luting), and color change was calculated according to the Commission Internationale de l'Eclairage (CIE) CIEDE 2000 formula and translucency parameters. The statistical significance of color change and viscosity was measured using 2-way analysis of variance (ANOVA), while the degree of conversion was measured using 1-way ANOVA. For translucency parameters, ANOVA on ranks and post hoc Duncan multiple range tests were performed. The control group showed the highest degree of conversion, while Filtek Z350 showed the highest viscosity. Statistically significant differences in color change between luting material groups were found under most conditions (P < 0.001), but there was no difference in translucency parameters between the luting materials (P = 0.446). Overall, the use of preheated composite resins as luting agents offers similar to poorer performance than conventional resin cement.