Change of dentin surface by low-power irradiation of erbium- doped yttrium aluminum garnet laser

Akira Nakane, DDS, Masayuki Otsuki, DDS, PhD, and Junji Tagami, DDS, PhD

Cariology and Operative Dentistry, Department of Restorative Sciences, Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan

Purpose: The objective of this study was to evaluate the effect of low output power irradiation of erbium-doped yttrium aluminum garnet (Er:YAG) laser on surface morphology, roughness, and microhardness of the root dentin.

Materials and Methods: Flat root dentin surfaces were prepared from extracted human molars. The surfaces were irradiated by an Er:YAG laser at 10 pps, 30 mJ, sweeping at approximately 2 mm/s by hand. Irradiated power was changed by means of the distance between laser tip and surface kept at 0, 5, 10, 15, 20, 25, 30, 35, and 40 mm. No irradiated surface was employed as control. Those surfaces and crosscut surfaces were observed by a scanning electron microscope (SEM). Specimens of irradiation distance at 0, 5, 10, 20, 30, and 40 mm and control (no irradiation) were further prepared and then, surface roughness (Ra) and microhardness (Vickers hardness) were measured.

Results: Ablation of dentin was observed at distance between 0-15 mm. At 20-30 mm, degenerated layer was observed without ablation. At 35 and 40 mm, ablation and degenerated layer were not found. Ra values of all experimental groups (0-40 mm) showed statistically higher than that of control group (p < 0.05). Among the experimental groups, 0 mm group showed statistically higher Ra values than the other groups (p < 0.05). For Vickers hardness, no significant difference was found all groups except 0 mm group (p > 0.05).

Conclusion: It was concluded that specific low output power Er:YAG laser irradiation produced thin degenerated layer on the root dentin without ablation. This irradiated surfaces showed slight increase of roughness without decrease of microhardness.
(Asian Pac J Dent 2019; 19: 33-37.)
Key Words: Er:YAG laser; low level laser therapy; root dentin