| Co-Investigator(Kenkyū-buntansha) |
HATORI Masasi Showa university, School of Dentistry, Assistannt Professor, 歯学部, 助手 (20245814)
SAKAMAKI Hideaki Showa university, School of Dentistry, Assistannt Professor, 歯学部, 講師 (50201520)
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| Budget Amount *help |
¥3,000,000 (Direct Cost: ¥3,000,000)
Fiscal Year 1998: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1997: ¥2,500,000 (Direct Cost: ¥2,500,000)
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| Research Abstract |
The animals used were female japanease white rabbits. Twenty-four rabbits were divided into an experimental group and a control group. In the experimental group, after performing ovariectouiy, rabbits were fed a low-calcium diet containing 0.15% Ca. In the control gruop, rabbits were received a normal diet. Bone mineral dencity of the mandible of a rabbit was measured using DEXA (Dual Energy X-Ray Absorptiometry). It was found that the bone mineral density was smaller by about 20% in the experimental group than in the control group. Next, after the mandible of rabbits in both groups was exporsed, artificial fracture was created using an electric motor and a bone chisel. Then the fracture was reduced by manipulation and the fragments were fixed with titaniun microplates with four holes and screws. The animals were sacrificed immediately, 1 week, 2 weeks. 4 weeks and 8 weeks postoperatively, and the differences in the bone healing process between the two groups were examined by radiograp
… More
hy as well as by histological examination of nondemineralized sections.
It was found that there were no significant differences in the radiographic findings of the specimens taken within 2 weeks after surgery. However, in specimens taken at 4 and 8 weeks after surgery, radiolucency was higher in the experimental group. Histological examination revealed that callus formation started at the end of the fragments in the fracture line, and that there was marked formation of bone trabeculae from 2 to 4 weeks after surgery. At 4 weeks after surgery, osteoid formation was noted in the fracture line presenting irregular patterns of trabeculae. At 8 weeks after surgery, the bony union was almost complete, and almost normal lamination was noted although exhibiting partly irregular patterns in the experimental group. Histological examination revealed that the activity of bone formation was slightly lower in the experimental group compared to the control group. These results were in agreement with the differences in radiolucency. It was suggested that the fracture healing of the jow bone may be delayed when the bone mineral density is decreased. In clinical practice, extention of the fixation period may be necessary when the bone
mineral density is low. Less
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