Objective: The objective of this study was to evaluate the efficacy of Nd:YAG laser to remove debris and smear layer on the instrumented root canal walls in vitro.
Summary background data: There have been some contradictory reports about the efficacy of Nd:YAG laser to remove debris and smear layer.
Materials and methods: Thirty-six extracted single mandibular incisor human teeth were used in this study. The teeth were sectioned at an enamel-cementum junction and the roots were instrumented up to # 50-K files size, then divided into three groups of 12 teeth. The first group (Group 1) was unlased as a control, and in the other two groups, root canals were irradiated by Nd:YAG laser at two different parameters; 1 W, 20 pps (Group 2) and 2 W, 20 pps (Group 3). After laser irradiation, the roots were bisected longitudinally, observed by scanning electron microscopy, and evaluated the condition of cleanliness on the root canal walls according to our criteria.
Results: In most of the specimens in Groups 1 and 2, debris and smear layer remained on the root canal wall surfaces covering the orifices of dentinal tubules. However, specimen in Group 3 showed very clean root canal walls with debris and smear layer evaporated, melted, fused, and recrystallized in most cases. Statistical analysis demonstrated a significant difference between Groups 1 and 3.
Conclusions: These results suggest that Nd:YAG laser is useful to remove debris and smear layer and causes melting of internal structures on the instrumented root canal walls at the parameters of 2 W and 20 pps.