Abstract
This study evaluated the bond strength (BS) of experimental resin cements formulated with different photoinitiators when activated by two kinds of light-curing units (LCUs) through a ceramic material. Seven resin blends with different camphorquinone (CQ) and/or phenylpropanedione (PPD) concentrations (weight) were prepared: C5: 0.5% CQ; C8: 0.8% CQ; P5: 0.5% PPD; P8: 0.8% PPD; C1P4: 0.1% CQ and 0.4% PPD; C4P1: 0.4% CQ and 0.1% PPD; C4P4: 0.4% CQ and 0.4% PPD. Two LCUs were used: one quartz-tungsten-halogen (QTH - 850 mW/cm²) and one light-emitting diode (LED - 1300 mW/cm²). The microtensile bond strength of each blend was assessed. Data were submitted to two-way ANOVA and Tukey's test (α=0.05). The BS values did not exhibit significant differences for LCUs, regardless of the photoinitiator type. Three cements showed significant differences: P5 and C5 had higher BS with QTH, and C4P1 with LED. For QTH, P5 showed the highest and C1P4 the lowest BS. For the LED, C4P1 showed the highest BS of all the cements. The results indicated that PPD was a viable alternative in the formulation of photocured resin cements, reducing or eliminating CQ that is yellowish without impairing the bond strength. Furthermore, both LED and QTH were effective in curing resin cements that contain PPD or CQ.
Highlights
The use of indirect ceramic restorations is increasing due to their superior aesthetics, biocompatibility and long-term stability
Three cements (C5, P5 and C4P1) showed significant differences in bond strength (BS) when activated by each light source
Independent of the light-curing units (LCUs) factor, for QTH P5 showed the highest BS with statistically significant difference from C1P4
Summary
The use of indirect ceramic restorations is increasing due to their superior aesthetics, biocompatibility and long-term stability. “Etchable” ceramic restorations should be adhesively luted, as doing so improves the retention, marginal sealing and fracture resistance [1]. The success of resin-bonded, all-ceramic restorations is highly dependent on obtaining a reliable bond and good polymerization [2]. Two sorts of resin cements - lightcured and dual-cured - have been used for luting indirect ceramic restorations. Dual-cured cements have shown to be dependent on the light exposure to ensure their best properties, similar to those that are light-cured [3]. The light-cured resin cements can be selected for fixing ceramic veneers on anterior teeth, because they allow more light to pass through, which helps to assure good bond strength. Akgungor et al [4] concluded that up to 2 mm thick , light curing has no deleterious effect on BS
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