IADR Abstract Archives
Cutting Edge Microscopic Imaging of Endodontic Instruments in Root Dentine
Objectives: We have imaged tooth-cutting interactions microscopically for over twenty five years using a variety of microscopic techniques; in particular, video-rate confocal microscopy. The aim of this study was to develop these techniques for evaluating the different cutting interactions of modern powered rotary endodontic instruments.
Methods: The technique uses the video frame rate capabilities of a tandem scanning confocal microscope for reflection imaging. A special apparatus has been designed to fix a transversely sectioned root facing the objective lens whilst mounted inside a brass ring, held rigidly at the focal point of the long working distance lens being used. A gentle air stream may be used for chip clearance, or not – if the development of chips and debris is required. The file is introduced into the root canal space and then the end view of the cutting process observed. This setup allows imaging of the root dentine inner surface in contact with the shaping endodontic files while recording the cutting process using a high speed camera. Captured videos can be used to evaluate the cutting process in separate image frames and allow evaluation of the cutting process in the dentine. A variety of different cutting geometries have been evaluated during root canal preparation.
Results: Using this set-up in the form of an open system has allowed debris collection for chip and wear particle analysis. We have been able to observe microstructural changes such as crack formation and propagation within the root dentine. The continuous clearance of debris, however, does not imitate the instrumentation in the closed system of root canals in-vivo. Our cutting experiments are likely to produce an optimised result, but the clinical situation could be even worse.
Conclusions: This imaging technique has the potential to provide a better understanding of the nature of the interaction between endidontic shaping instruments and root dentine. This may help correlate the clinical performance of endodontic files with their impact on cut dentine. It also allows the observation of microscopic changes affecting the dentine, such as micro-crack formation and propagation.
Methods: The technique uses the video frame rate capabilities of a tandem scanning confocal microscope for reflection imaging. A special apparatus has been designed to fix a transversely sectioned root facing the objective lens whilst mounted inside a brass ring, held rigidly at the focal point of the long working distance lens being used. A gentle air stream may be used for chip clearance, or not – if the development of chips and debris is required. The file is introduced into the root canal space and then the end view of the cutting process observed. This setup allows imaging of the root dentine inner surface in contact with the shaping endodontic files while recording the cutting process using a high speed camera. Captured videos can be used to evaluate the cutting process in separate image frames and allow evaluation of the cutting process in the dentine. A variety of different cutting geometries have been evaluated during root canal preparation.
Results: Using this set-up in the form of an open system has allowed debris collection for chip and wear particle analysis. We have been able to observe microstructural changes such as crack formation and propagation within the root dentine. The continuous clearance of debris, however, does not imitate the instrumentation in the closed system of root canals in-vivo. Our cutting experiments are likely to produce an optimised result, but the clinical situation could be even worse.
Conclusions: This imaging technique has the potential to provide a better understanding of the nature of the interaction between endidontic shaping instruments and root dentine. This may help correlate the clinical performance of endodontic files with their impact on cut dentine. It also allows the observation of microscopic changes affecting the dentine, such as micro-crack formation and propagation.