Evaluating the effect of ceramic veneer thickness on degree of conversion in three luting resin cements

Introduction: The purpose of this study was to compare the effect of different ceramic thicknesses on degree of conversion (DC) of 3 light-cured resin cements. Methods: In this experimental in-vitro study, the degree of conversion of three light-cured resin cements, Variolink Veneer (Ivoclar, Liechtenstein), RelyX Veneer (3M ESPE, USA) and Choice2 (Bisco, USA) were evaluated beneath feldespatic ceramic discs (Vita VMK Master) with a same shade, 2m2, in different thicknesses (0.5, 1, 2 and3 mm) using FTIR. The light curing unit used was Optilux 501, with an intensity of 600 mW/cm2 and exposure duration of 40 seconds. Three specimens of each cement group were examined in each condition. The obtained data was submitted to Kolmogorov-Smirnov and also checked for absence of skewness and kurtosis for normal distribution. After that, ANOVA test was used for comparison between experimental groups (Tukey HSD). Results: In all the three used cements, DC decreased as ceramic thickness increased. This reduction was not significant when using 0.5 and 1 mm ceramic discs, however, it was significant between 1, 2, and 3mm discs(p 0.05). There was no difference within the cements’ DC when exposed through ceramic discs of 0.5, 1, and 2mm, but the Rely X Veneer cement had a lower DC compared to Variolink Veneer and Choice2 when the thickness increased to 3mm(p 0.05). Conclusion: It is not advisable to use light-cured resin cements beneath 3 mm thick ceramics and the use of Rely X Veneer is not recommended as the ceramic thickness increases