Comparison between the removal effect of mechanical, Nd : YAG, and Er : YAG laser systems in carious dentin

Objective: The purpose of this study was to compare the effectiveness of ca rious dentin removal by using an Er:YAG laser irradiation and Nd:YAG laser under a continuous water spray with that of the conventional mechanical tre atment in vitro. Background Data: Lasers are being considered as a potentia l replacement of conventional mechanical systems to remove diseased and hea lthy dental hard tissues. Methods: First, one half of the 10 carious lesion s were treated with the round steel bur and then removed. The other half we re treated with the Er:YAG laser at 200-mJ pulse energy at 2 Hz. After that , one half of another set of 10 teeth was subjected to the round steel bur in which the other half was removed using the Nd:YAG laser at 6-W output po wer, 20 pps, and under a continuous water spray (120 mL/min). Thermal chang e during each treatment and the time required for carious dentin removal wa s determined, and the surface characteristic was observed using the scannin g electron microscopic (SEM). Results: The Er:YAG or Nd:YAG laser irradiati on time was almost two or three times longer than the bur treatment, respec tively. From the SEM study, it was found that the lased cavity surface reve aled various patterns of microirregularity, and there was also no smear lay er. Conclusions: It can be suggested that under adequate water spray and wi th a careful irradiation technique, cavities without sign of thermal damage to the surrounding tissues as well as dental pulp could be produced with t he Er:YAG and Nd:YAG laser.