SCANNING ELECTRON-MICROSCOPY AND THERMAL-CHARACTERISTICS OF DENTIN ABLATED BY A SHORT-PULSE XECL EXCIMER-LASER

The interaction of a short pulse XeCl excimer laser radiation with hum an dentin was investigated. The dependence of surface temperatures and temperature gradients into the treated teeth on laser parameters such as fluence (0.5J/cm2-7J/cm2), pulse repetition rate (1Hz-35Hz), and s pot size (0.004cm2-0.12cm2) was studied. Additionally, the effect of f luence and pulse repetition rate on dentin microstructure was studied using scanning electron microscopy (SEM). It is demonstrated that this ''cold ablation'' excimer laser can result in significant thermal mod ification in the dentin surfaces. Changes include the formation of mel ted dentin grains, which uniformly cover the surface and the exposed d entin tubules. Maximum temperatures of the ablated surfaces, however, remained relatively low at most laser parameters used. Also, the immed iate neighborhood of the root canal was essentially undisturbed at mos t laser parameters. These observations suggest that with the appropria te choice of parameters XeCl lasers can be effective in producing surf ace structures that may prove useful in enhancing bond strength or oth er applications in dentistry, without exposing tooth pulp to significa nt temperature elevation.