| Budget Amount *help |
¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 1997: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1996: ¥900,000 (Direct Cost: ¥900,000)
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| Research Abstract |
This study was performed on the following two parts.
1.Observations of the fragments obtained from the fractured molars in-vivo.
The fragments were obtained from the first molars of the patients suffering from vertical fracture (case 1,2,3). They were subjected to the fractographycal analysis through optical and SEM observations, obtaining the following findings.
On the individual fractured surfaces, various structures were observed. Namely, in case 1, manywave-shaped structures were found running in parallel with dentinal tubules. In case 2, rib-marks of various size and small hackle marks were found around apical area and coronally propagating. In case 3, many river patterns were found initiating coronally and apically running, inacreasing their sizes.
2.Observations of the experimentally fractured tooth surfaces
The extracted human upper central incisors were horizontally sectioned around the cervix. Then, the root was vertically split coronally (group 1) or apically (group 2) with a knife and mallet.
In group 1, many river patterns were found apically running, increasing their sizes and diverting laterally. In group 2, rib marks were found initiating together with many hackle marks, propagating coronally.
Analysis of the findings seems to indicate that the in-vivo molars rapidly fractured presenting the brittle fracture patterns.
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