In vitro investigation of intra-canal dentine-laser beam interaction aspects: II. Evaluation of ablation zone extent and morphology.

Laser endodontic tips appear to provide a promising alternative to available treatment modalities in the field of endodontology. With the shortcomings in published results regarding the intra-canal behavioural aspects of those tips, it was the aim of this study to investigate the extent of the intra-canal ablation zone and the pattern associated with those tips. Ninety intact extracted bovine teeth were used to prepare mid-root testing cylinders. The samples were divided into three groups (A, B, C), corresponding to the tip diameters. Each group was further subdivided to be irradiated at three different power settings (1500 mW, 1750 mW, 2000 mW) with an erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) laser with a 65% water to 35% air ratio. Collected data were subjected to analysis of variance (ANOVA) and the Tukey test. At a chosen significance level of alpha = 1%, no statistical difference was found among the groups (P > 0.01). The results suggest that shortening of the estimated working length is mandatory for the use of those tips within the canal, and that, provided that certain measurements are used for intra-canal laser ablation, this is a secure mode of treatment. Further investigation and system improvement will be required for more satisfactory results.

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.

In vitro preliminary study to evaluate the capability of Er,Cr:YSGG laser in posterior teeth root-canal preparation with step-back technique.

This preliminary study was to investigate in vitro the Er,Cr:YSGG laser ablation capability, both range (enlargement aspects of laser tips corresponded to conventional endodontic files) and quality (removing of smear layer and opening of dentinal tubules) to clean and shape the root canal for final obturation step. The crowns of 15 extracted multi-rooted posterior human teeth were resected, and then 15 canals were prepared by an Er,Cr:YSGG laser up to 1.5 W (actual power output) using the step-back technique, while the other 15 canals (control) were enlarged conventionally by K-flex file. The results revealed that posterior root-canal preparation could be achieved by laser beam transmitted to the canal using endodontic tips. At a chosen significance level of alpha = 1%, the results showed no significant statistical difference between the two groups (P > 0.01). Considering the results of this current study, laser-based root-canal preparation still shows certain limitations, and further improvements are mandatory for higher achievement and better preparation outcomes.