Influence of laser irradiation on the constant composition kinetics of enamel dissolution

The influence of 9.6 microm CO2 laser irradiation on enamel dissolution kinetics was investigated using a constant composition method designed for rate measurements of enamel dissolution as a function of depth, on a micrometer scale. In contrast to lower irradiation intensities (< or =1.0 J cm(-2)), which consistently showed reduced dissolution rates, higher fluences (energy per surface area) resulted in initially increased dissolution rates, which rapidly decreased, after dissolution times corresponding to removal of a few micrometers, to rates similar to those acquired using lower fluences. It was also demonstrated that surface damage during laser irradiation could be limited to the first 1-2 microm by lowering the number of pulses per spot during the irradiation procedure. The constant composition method can be used to measure detailed kinetics of inhibition of acid dissolution of dental enamel that has been treated by low fluence 9.6-microm CO2 laser irradiation.