Evaluation of the Hardness of Infected Root Canal Dentin with Fluorescence Excitation

抄録

 Purpose: This study aimed to evaluate the association between infection and hardness in root canal dentin by irradiating infected root canal dentin with blue light at a wavelength of approximately 405 nm.

 Methods: A total of 10 healthy human extracted teeth and 10 human extracted teeth with infected dentin were used as samples and semi-cut sections were prepared as longitudinal sections of the root canal. The root canal walls were observed using a stereo microscope under blue light at a wavelength of approximately 405 nm to measure the fluorescence spectrum and Vickers hardness. Subsequently, the area was observed using a scanning electron microscope.

 Results: In teeth with infected root canals, blue-light irradiation at a wavelength of approximately 405 nm induced fluorescence excitation at wavelengths of approximately 620 and 680 nm. In the healthy teeth, no significant difference was observed in Vickers hardness in the region with fluorescence excitation of up to 500 μm from the root canal wall; however, in the infected teeth, a significant decrease in Vickers hardness was observed in the region with fluorescence excitation of up to 500 μm from the root canal wall. Furthermore, in the infected teeth, a bacterium-like structure was observed via electron microscopy on the root canal wall surface, and in the dentin tubules in areas with fluorescence excitation, whereas in areas without fluorescence excitation, there were few bacterium-like structures.

 Conclusion: This study suggests that blue light of approximately 405-nm wavelength is useful in detecting infected areas in the root canal wall.