Photoinitiator system and water effects on C=C conversion and solubility of experimental etch-and-rinse dental adhesives

Abstract The purpose of this study was to determine the influence of the photoinitiator system and moisture condition on the degree of C=C conversion (DC), the water sorption (W sp ), and the solubility (W sl ) of experimental two-step etch-and-rinse dental adhesives. Different photoinitiator systems were added at 0.5 mol% to an experimental adhesive blend (55:45 wt% Bis-GMA:HEMA), defining the experimental groups: camphorquinone (CQ)+ethyl-4-dimethylaminobenzoate (EDMAB), 9,10-phenanthrenequinone (PQ), PQ+EDMAB, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), and phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO). The adhesives were tested in two moisture conditions: neat and wet (with the addition of 10 wt% D 2 O). The DC ( n =6) was evaluated by Fourier-transformed infrared spectroscopy (FTIR). W sp and W sl were determined ( n =10) after successive weighting procedures. Data were submitted to two-way ANOVA and Tukey׳s post hoc test ( α =0.05). Pearson׳s correlation tests were used to analyze the correlation between DC and W sp or W sl . TPO and BAPO presented the highest DC in the neat condition while CQ+EDMAB presented the highest in the wet condition. W sp and W sl were both dependent on the photoinitiator system and moisture condition. PQ–based materials presented the highest W sp and W sl in both neat and wet conditions. Pearson׳s tests were not able to detect any significant correlation between DC and W sp or DC and W sl . Within the limitations of the present study, it can be concluded that the photoinitiator system and moisture condition influenced the DC, W sp , and W sl of experimental two-step etch-and-rinse adhesives.