Laser-induced temperature changes in dentine

The purpose of this work is to study the temperature rise and potential thermal damage caused during ablation of human dentine using a super pulsed carbon dioxide laser of 9.6-microm wavelength, equipped with a water-cooling spray and scanner system. There have been no reports on thermal effects of super pulsed CO2 laser of 9.6 microm wavelength on human dentine recently. Two different types of samples were investigated to yield data most consistent with a typical clinical situation. Human dentine slices and crown segments were studied at a drilling depth of 1.0 +/- 0.1 mm and 2.5 +/- 0.5 mm, respectively. A control group treated with a conventional hand piece was compared to four laser groups with settings varying from 2 to 8 W. In the laser group demonstrating the highest elevation in temperature of the four studied, dentine slices lased at 2 W for 15 sec showed a mean temperature rise of less than 1.68 degrees C at an ablation rate of 0.86 +/- 0.08 mm. Conventional drilling with a comparable ablation rate of 0.76 +/- 0.59 mm resulted in a mean rise of 2.87 degrees C. The laser groups of crown segments revealed a constant decrease in temperature. SEM observations were lacking the typical morphological changes seen in earlier studies, specifically extensive melting, charring or cracking. A maximum rise of mean temperature to 1.68 degrees C in closest vicinity to the pulpal chamber and the morphological unaltered dentine surfaces demonstrate the safe and tissue preserving character of the superpulsed 9.6 microm CO2 laser. The laser caused an even lower temperature rise than conventional drilling. Moreover, the laser showed acceptable efficacy with ablation rates that did not significantly differ from the conventional dental drill.