Papers by Author: Keyoung Jin Chun

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Authors: Keyoung Jin Chun, Ho Jung Li
Abstract: Mandibular first premolars in superlative state were scanned by a Micro-CT. Data were obtained from the scanned 2-D images, and reconstructed into 3-D models for FEA, at which point stress distribution of the inner and outer part of the tooth were shown. It was found that when compared with the teeth data used as a standard by G. V. Black, the aspect of the external morphology of the teeth is comparatively small regardless of gender. Also, differences exist between the Micro-CT data and G. V. Black’s data. This study also presents the internal morphological data that was not shown in G. V. Black’s data. The dentin size is larger than the enamel size in both males and females in the case of the internal morphological data. It is found that the stress was concentrated on the cervical line, and the stress varied around the boundary between dentin and enamel within the teeth. It is also revealed that the stress varied at the boundary surface between dentin and pulp. The results using a Micro-CT and stress analysis may reveal the cause of the abfraction, and bring up a guideline for endodontic treatment.
Authors: Keyoung Jin Chun, D.L. Butler
Abstract: An understanding of the mechanical responses of the patellar tendon (PT) subunits should aid in determining which portion of the tissue might best be used as a cruciate ligament replacement. Human cadaveric knees were obtained from young donors. Fascicle groups with patellar and tibial bone blocks (subunits) were cut to provide six equally-spaced test specimens for each PT. After potting each bone end in PMMA, specimens were mounted in a saline-filled chamber, preloaded to 0.26 N and then subjected to 40 cycles of preconditioning to 2.5 % of the initial length at a strain rate of 1.25 %/sec, and then preloaded to 0.26 N again and failed at a strain rate of 100 %/sec using an Instron. The moduli and maximum stresses were generally greater in the lateral and mid subunits than in the medial subunits. The strains to maximum stress were similar between the lateral and medial subunits, but mid subunits had larger strains. Most strain values were distributed between 10 % to 20 %. Mechanical responses of human PT do vary from location to location. In general, the mid and lateral subunits were stiffer and carried greater stresses than the medial subunits. The results of this research should eventually be important, e.g. in selecting which portion of the PT would be the most suitable for cruciate ligament replacements to use as an autograft. On the basis of strength and stiffness, the more lateral portion of the PT would seem to be more advantageous.
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