THE SMEAR LAYER REMOVAL EFFECT OF HYDROXYL RADICALS GENERATED FROM HYDROGEN PEROXIDE IRRADIATED WITH 405-NM LED LIGHT

抄録

In this study, we investigated whether it is possible to remove the smear layer using hydroxyl radicals (•OH) generated by photochemical reactions. Hydrogen peroxide (H₂O₂) was irradiated with a 405-nm light-emitting diode device to generate •OH. The amounts of •OH generated during irradiation for 10, 20, and 30 s were measured using the electron spin resonance spin-trapping method, and the amounts were compared between the H₂O₂ group (H₂O₂ without irradiation) and •OH group (H₂O₂ with irradiation). In addition, 14 smear specimens were prepared from seven roots; the specimens were treated with the H₂O₂ group, •OH group and control group (PBS only) for 3 min, then the root canal surfaces were observed by scanning electron microscopy.

In the •OH-group, the amount of •OH generated was increased by the irradiation in a time-dependent manner; the smear layer was partially removed, and a few dentin tubules were observed. In contrast, almost no •OH was generated in the H₂O₂ group. The root canal surfaces of the control and H₂O₂ groups were densely covered with a smear layer, and no dentin tubules were observed.

These results suggested that the •OH generated by the photochemical reaction can remove the smear layer.