Effects of diode laser irradiation on smear layer removal from root canal walls and apical leakage after obturation

The objective of this study was to investigate the rise in temperature in root surfaces during and immediately after diode laser irradiation, to observe morphological changes of root canal wall after irradiation, and to evaluate the apical leakage after irradiation and obturation in vitro.

There have been very few reports on root canal treatment by 980-nm wavelength diode laser.

Sixty-six extracted human single-rooted teeth were instrumented up to size 60 K-file, and then randomly divided into three groups of 22 teeth each. Groups 1 and 2 were irradiated with a diode laser at 5 W for 7 sec using fibers of diameters 550 and 365 microm, respectively. Group 3 was not irradiated, and served as a control. The rise in temperature on root surfaces of the teeth in groups 1 and 2 were measured by thermography. Six teeth in each group were bisected longitudinally and observed morphologically. Other teeth were obturated and immersed in rhodamine B solution, and the degree of apical leakage was evaluated longitudinally and transversally.

A maximum temperature rise of 8.1( degrees )C was recorded in group 1. The smear layer in the laser-treated groups was evaporated and removed, resulting in clean root canal walls, which was significantly superior to the control group (p < 0.05). After obturation, the laser-treated groups showed significantly less apical leakage than the control group (p < 0.05).

These results indicate that the diode laser is useful for removing smear layer and debris from root canal walls, and reducing apical leakage after obturation in vitro, and suggest that it would be useful for root canal treatment in clinic.