The Effect of Intracanal Disinfection by Er: YAG Laser Irradiation

Abstract

A variety of contact tips made of quartz have been developed to transmit laser beams more effectively on specific areas. This may increase the potential usefulness of the Er: YAG laser for root canal treatment. The purpose of this prelimi nary study was to investigate the performance of Er: YAG laser irradiation with narrow contact tips for root canal disinfection. Twenty seven bovine anterior tooth roots were used. The root canals were inoculated with 0.1 ml of kanamycin-resistant E. coli solution (2.0×10⁸ CFU/ml) after the apex was sealed with acrylic resin. The root canals were irradiated by Er: YAG laser (Erwin Adverl, Morita) with two kinds of contact tips (P400FL and R300T). The contact tip was placed in the root canal, and irradiated for 30 seconds three times without water spray under up-and-down motions between 0 and 3 mm from the apex. Output energy was standardized at 30 mJ, and pulse frequency was 10 pps. No irradiated samples were used as control. The maximum temperature elevation was measured by a thermo-couple during the procedure. After the laser irradiation, 0.05ml of the Intracanal solution from each sample was cultured in LB agar plate for 24 h. The colony forming units in each sam ple were counted. In addition, the surface of the irradiated area was observed under a light microscope and a scanning electron microscope. The mean CFUs for P400FL, R300T and control groups were 3.0±1.7×10⁷, 6.5±6.3×10⁷ and 9.0±6.2×10⁷ CFU/ml, respectively. There was a statistically significant difference between the P400FL and control group. The irra diated surfaces using P400FL showed vaporized dentin, but no carbonization was observed, while those using R300T showed little change. The maximum temperature elevation was less than 5°C in all groups. These results suggest that Er: YAG laser irradiation could be used for root canal disinfection safely and effectively.