| 2715 Effect of Heating on Mechanical Properties of Human Dentin | ||
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K. OKAMURA1, M. HAYASHI1, E. KOYTCHEV1, A. SUGETA2, and S. EBISU1, 1Osaka University, Suita, Japan, 2Hiroshima University, Higashi-hiroshima, Japan Objectives: A better understanding of the mechanical properties of human dentin in various environmental conditions could significantly help in preventing tooth fracture. The purpose of this study was to investigate the effects of dehydration and heating on the flexural and tensile strength of dentin by focusing on dentinal tubule orientations. Methods: Beam-shaped dentine specimens were obtained from the coronal parts of freshly extracted human third molars. Dentinal tubule orientations of the specimens were organized to run parallel or perpendicular to loading surfaces. The specimens were kept in one of the following environmental conditions: wet - soaked in HBSS; dry - dried in a desiccator for 1week at 23°C; heat - heated in an oven at 50, 70, 110, or 140°C for 1h. Specimens were subjected to a flexural fracture test and a micro-tensile test by a universal testing machine, followed by fractographic observation by SEM. The fracture strength of specimens taken from different environments were compared by means of ANOVA and Scheffe's F test at a 95% level of confidence. Molecular structure distributions before and after the heat treatments were analyzed by an X-ray diffraction microscope. Results: The flexural and tensile strength was significantly increased by the heat treatment within the range from 70 to 140°C, particularly in the parallel specimens. According to the SEM observation, wet specimens showed flat fracture surfaces with clear dentine microstructures; while heated specimens presented rougher surfaces. X-ray diffraction analysis demonstrated the shrinkage of distance between collagen fibrils after the heat treatment. Conclusion: The mechanical properties of human dentin were increased by the heat treatments due to the shrinkage of collagen networks. (This work was supported by a Grant-in-aid for Scientific Resarch (16390546) from the Japan Society for the Promortion of Science) | ||
| Seq #282 - Tooth, Biocompatibility 10:45 AM-12:00 PM, Saturday, March 24, 2007 Ernest N. Morial Convention Center Exhibit Hall I2-J | ||
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