Abstract
Abstract The aim of this study is to determine the optimum value of the laser powers and to determine the least possible time for irradiation at which upon then may obtain the maximum degree of shear bond strength of composite material with the tooth. Teeth groups where etched by continuous wave CO2 laser in different power and energy densities for each group, and one group was etched by phosphoric acid solution. Some of them were selected for study used for photography by using light microscope. After a bonding procedure for the remaining teeth, the teeth had been subjected to sheer bond strength tests by using a universal testing machine and the result were recorded in megapascal unit (Mpa). Under light microscope, we saw the patterns of enamel etching by laser similar to that of acid etching, but not uniform and some groups produce poor etch pattern, compared to that of acid etched enamel. The bonding force of composite material adhered to laser etched enamel is less than that for acid etched enamel.
