It has been a very important problem till now in dentistry to investigate the deformation of teeth and mandibular bones subjected to occlusal or masticatory forces. Various measuring techniques have been utilized to measure their deformation on idealized models or patient's masticatory systems. In this paper holographic interferometry is given as a suitable solution of the problem. Holographic interferometry makes it possible to investigate three dimensional deformation of diffusely reflecting objects interferometrically. The principle of measurement and the measuring accuracy are described and an experiment is performed on the teeth and the mandibular bone of a dog. The lower first molar is subjected to lateral tensile forces from three different directions. The exposed regions of teeth and mandible are coated with white paint to increase the reflectance of the surface. This overcomes the difficulty in forming interferograms of biological materials. The resulting interferograms are evaluated to determine he displacements of the teeth and the surrounding structure. Experimental results are quantitatively discussed for each lateral tensile force.
When tensile force is subjected perpendicularly to lingual surface of the first retromolar, it is found that teeth and mandible deformed considerably to lingual direction.
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