The effect of 808 nm diode laser irradiation on shear bond strength of composite bonded to dentin before and after bonding

Abstract

Objectives: As bonding ability to tooth surface is an important factor in durability of composite restorations, the aim of this in vitro study was to evaluate the effect of 808 nm diode laser irradiation with different power outputs on the shear bond strength of composite bonded to the dentin before and after applying the bonding agent. Materials and Methods: A total of 35 healthy third molars were mounted in acrylic resin in a way that each molar had two test sites and divided into seven groups of 10 each. In the control group, the bonding agent was used without laser application. An 808 nm diode laser with different power outputs of 0.5, 1 and 1.5 W for a duration of 20 s was irradiated perpendicularly to the dentin surfaces in three of the experimental groups before and in the other three groups after applying the bonding agent. After composite cylinders had been adhered, they were examined to determine their shear bond strength. Results: According to the least significant difference test, the bond strength mean significantly higher in the control group (P < 0.001) and in all laser power outputs, the mean bond strength was significantly higher in the groups for which laser was irradiated before applying the bonding agent than the groups for which laser was irradiated after applying the adhesive (P < 0.05). Conclusion: Considering the higher bond strength in the control group, it seems that applying laser does not increase the bond strength of composite to the dentin.