Effect of different photoinitiator systems on the mechanical properties of experimental resin cements

The objective of the present study was to evaluate the flexural strength, flexural modulus, and surface micro hardness of 3 experimental resin cements with different photoinitiator systems in comparison to a commercially available resin cement. Three experimental resin cements were prepared with a 50:50 wt% matrix to filler ratio and different photoinitiator systems: 0.5% camphorquinone (CQ) + 1 wt% N,N-dimethylaminoethyl methacrylate (DMAEMA); 1.26 wt% bisacylphosphine oxide (BAPO) + 1 wt% DMAEMA; or 1.26 wt% BAPO. A commercially available light-curable resin cement (RelyX Veneer) was used as control. For each resin cement, 10 bar-shaped specimens were manufactured to determine flexural strength and modulus, and 10 disc-shaped specimens were prepared to evaluate Knoop microhardness. Data were analyzed with 1-way analysis of variance followed by Tukey and Games-Howell tests (α = 0.05). The control resin cement showed significantly higher flexural strength than both BAPO-containing cements (P < 0.001). The flexural strength of the CQ + DMAEMA cement was significantly lower than those of the control and BAPO resin cements (P < 0.05) but was not significantly different from the value of the BAPO + DMAEMA material (P > 0.05). The flexural modulus of the BAPO cement was significantly higher than that of the CQ + DMAEMA cement (P = 0.021); however, neither cement was significantly different from the control or BAPO + DMAEMA groups (P > 0.05). Both BAPO-containing cements showed greater Knoop microhardness than the control, which in turn presented a greater value than the CQ + DMAEMA cement (P < 0.001). The results indicated that the type of photoinitiator system significantly changes the mechanical properties of light-curable resin cements. The BAPO-containing cements presented mechanical properties comparable or superior to those of the commercially available resin cement.