| Budget Amount *help |
¥6,400,000 (Direct Cost: ¥6,400,000)
Fiscal Year 1989: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1988: ¥5,900,000 (Direct Cost: ¥5,900,000)
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| Research Abstract |
The present study was made to investigate the initial bone remodeling and tissue response of the rat mandible to mandibular retractive force by means of lead-labelling technique, ultrasoft x-rays and three-dimensional analyzing system. Experimental rats were given the chin cap-like appliance and after that, they were sacrificed with the intervals of 5,10,15,20,30 days.
This study gave the following results;
1) At the initial stage after mandibular retraction, cephalometrically lower incisors elongated. After,that, mandibular body was strained and upward force from chin cap applied to anterior portion of the mandible. As a result of this phenomena, it appeared that the mandible rotated counterclockwise and anterior-downward growth of it was controlled.
2) Histologically, the condylar cartilage become gradually thinner and internal remodeling of the ramus was reduced. This indicated that cell proliferation was inhibited at the area of the condylar and ramus.
There was little bone deposition on the lower surface of the mandibular angle, but the bone in the transitional zone actively formed towards the outside.
3) The results from three-dimensional analyzing system was as follows; Slight concave shape was observed at the center of the condylar head and it was inclined deeper according to the wearing duration.
This finding supported the prediction on basis of histological one.
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