Method: IPS e-Max ceramic discs (Ivoclar Vivadent) were fabricated in 3 thicknesses (0.5, 1.0, and 1.5mm) and 4 opacities (HT, LT, MO, HO) (n=3/per group). Light-cured resin cement (Variolink Veneer Luting Cement – shade MVO, Ivoclar Vivadent) 50µm thick was cured through these ceramics disks using a halogen curing light unit (Optilux 501, Kerr) with its energy density and irradiance measured by MARC from a fixed distance (1.5mm). Knoop hardness and Raman microscopy were used to evaluate the bottom degree of cure. Descriptive statistics were conducted. One- and two-way ANOVA with post-hoc Tukey’s HSD test and Pearson correlation test were used for the statistical analyses (alpha=0.05).
Result: Significant interaction was found between ceramic thickness and opacity on resin cement degree of conversion (p<0.0001), irradiance (p=0.0062), and energy density (p=0.0078). Subsequent analyses demonstrated that there was a significant simple effect for opacity and for thickness on conversion, irradiance and energy density under different conditions of thickness and opacity. Although the curing unit used has relatively good beam homogeneity, no significant correlation was found between hardness and degree of conversion (r=0.03; p=0.8859) unless data collection locations of Raman and Knoop Hardness were taken in close proximity (R2= 0.9, p=0.0006). The calibration curve representing this correlation will be used in the final data collection.
Conclusion: Ceramic opacity and thickness affect the polymerization of light-cured resin cements and need to be considered and compensated for when bonding indirect restorations. Based upon the findings of this preliminary study, the final study is ongoing.
Keywords: Cements, Ceramics, Curing lights and Polymerization
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Signed on 10/07/2013 by L. ALGHAITH
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