Abstract
The aim of this study was to investigate the effect of the thickness of dentin (1, 2, or 3 mm) placed between the light guide and the composite resin on the shear bond strength to dentin treated with a simplified Gluma system. The effects of the thickness of composite resin (2 or 3 mm), irradiation time (20,40, or 60 sec), and shade (universal or brown) were also examined. The results showed that the thickness of dentin influenced bonding and interacted with the other three variables. It is suggested that dentin located between the light guide and composite resin may attenuate the light aimed at the bonding interface in the same manner as a layer of composite resin.