In vitro investigation of intra-canal dentine-laser beam interaction aspects: I. Evaluation of ablation capability (ablation rate and efficiency).

The aim of this study was to determine the amount of intra-canal dentine removed with an erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser using different endodontic tips and different power settings. Ninety intact extracted bovine teeth were selected as samples. After sectioning the roots and preparing the testing cylinders, we divided the samples into three main groups (A, B, C), with further subdivision of each group to be irradiated with three different powers (1500 mW, 1750 mW and 2000 mW). An Er,Cr:YSGG laser system (2.78 microm, 140 micros, 20 Hz and 65% water to 35% air ratio) was used for irradiation, and the loss of intra-canal dentine mass was calculated by the difference between the initial and final sample masses. Data were analysed with Kolmogorov-Smirnov, analysis of variance (ANOVA) and Tukey tests. At a significance level of alpha = 1%, the results showed statistically significant differences (P < 0.0001) between different tip groups, regarding both the ablation rate and the ablation efficiency criteria. With regard to the three irradiation power settings, statistically significant difference were recorded only between groups C and A, for the ablation rate criteria. The intra-canal ablation ability of the Er,Cr:YSGG laser improved with increasing power and/or tip diameter. The latter exhibited a stronger influence on ablation rate and efficiency. Laser intra-canal ablation is an important addition to the field of endodontics; nevertheless, further investigations and system improvements are required.