The purpose of this study was to evaluate the temperatures on the root surfaces during Nd:YAG laser irradiation in root canals using pulse durations of 180 and 320 μs. Thirty extracted human teeth were used in this study. The teeth were enlarged up to ISO 40 (multi-rooted) or up to ISO 60 (single-rooted) by conventional technique using K-files. Then the teeth were placed into a water bath with a constant temperature of 37 °C and then irradiated with an Nd:YAG laser having an output power of 1.5 W, a frequency of 15 Hz, using an optic fiber of 200 μm diameter. The temperature on the root surface was measured by means of attaching thermocouples in three areas (coronal, mesial, and apical regions) of the root canals. The thermographic study showed that the average temperature elevation for both pulse durations on the root surfaces was less than 9 °C. There was no significant difference in the observed temperatures in coronal and mesial areas. Though a higher increase of temperature was observed in the apical region when the pulse length of the Nd:YAG laser was 320 μs. The results of the study showed that the temperature rises during Nd:YAG laser irradiation with parameters used in this study minimal to cause damage on bone and periodontal tissues. Moreover, it was suggested that in order to have lower temperature in the apical region, an Nd:YAG laser with a pulse length of 180 μs is preferred than one with a pulse length of 320 μs.

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The purpose of this study was to evaluate the thickness and qualitative characteristics of the hybrid layer after two cavity preparation methods, using Er:YAG laser in QSP mode and conventional carbide burs. Additionally, two different adhesive techniques were investigated using etch-and-rinse and self-etch adhesive systems. Sixty sound human third molars were used and were randomly divided into four groups (n = 15). In the first two groups, large (4 mm length, 3 mm wide, and 3 mm deep) class I cavities were prepared using Er:YAG laser (2.94 μm) in QSP mode, while in the other two groups, the cavities were prepared using carbide burs. After cavity preparations, two different adhesive techniques with GLUMA® 2 Bond (etch-and-rinse) and Clearfil™ Universal Bond Quick (self-etch) were applied. For the qualitative evaluation of the formed hybrid layer, photomicrographs were taken using SEM, and elemental semi-quantitative analysis was performed using EDS to confirm the extent of the hybrid layer. One-way ANOVA was applied to verify the existence of statistically significant differences, followed by Tukey test for post hoc comparisons (Bonferroni corrected), and the level of significance was set at a = 0.05. The laser-treated groups exhibited higher hybrid layer thickness than bur-treated groups (p < 0.001). Between the laser-treated groups, etch-and-rinse technique presented higher hybrid layer thickness than self-etch technique (p < 0.001), while between the bur-treated groups, no significant differences were detected (p = 0.366). Er:YAG laser cavity preparations in QSP mode may be advantageous for adhesion of composite restorations, but more data are necessary to confirm its clinical effectiveness.

Aim: This ex vivo study compared the efficiency of Er:YAG laser to remove calcium hydroxide from root canal walls, especially from the apical third, with manual and ultrasonic irrigation technique by using a scanning electron microscopic (SEM). Materials and methods:Sixty-four single-rooted teeth were divided into 3 groups of 20 teeth each. The rest 4 teeth were used as control groups (2 positive and 2 negative control group). After coronal access, all teeth were instrumented by Protaper Next rotary files (Dentsply-Maillefer, Ballaigues, Switzerland) up to size F3, followed an irrigation protocol and filled with pure calcium hydroxide powder mixed with saline. Teeth were stored in an incubator for 7 days and then calcium hydroxide was removed using 3 techniques: Manually (group I), by ultrasonic irrigation (group II), by laser Er:YAG and x-pulse tip (group III). The teeth of control groups were instrumented as the experimental groups; no removal technique was applied in positive group, whereas in negative one, the root canals were left empty. Teeth were sectioned longitudinally and observed under SEM. Results were statistically analyzed with the Kruskal-Wallis test and Mann-Whitney test. Results:The results showed significant difference between laser and the other two groups in coronal and middle root third, but no statistic difference in apical third. Conclusion:Laser improved the removal of calcium hydroxide in comparison with conventional techniques.

Nowadays, dental treatment has been enriched by the use of lasers. The introduction of the novel treatment parameter of quantum square pulse (QSP) constitutes an additional challenge to older techniques, promising minimally invasive treatments. The aim of this study is to comparatively investigate the quality of cavity preparations using erbium-doped yttrium-aluminumgarnet (Er:YAG) laser with QSP technology as opposed to the conventional bur. The Er:YAG laser (2940 nm) has been used at 120 mJ energy level in QSP and medium short pulse (125 µs) modes. Subsequently, the dentin and enamel surfaces were examined using scanning electron microscopy techniques and compared with cuttings prepared with conventional bur. The laser-treated dentin samples exhibited relatively homogenous surfaces without smear layer and with open dentinal tubules. Laser-treated enamel showed scaly surfaces but again free of smear layer. In contrast, both dentin and enamel samples treated with the conventional bur showed abundance of smear layer, groove marks, small-scale cracks, and closed dentinal tubules.