Objectives: Bone changes at the residual alveolar ridge under the denture have not been fully elucidated. This study aimed to reveal the dynamic change of bone metabolism under the denture base using bone scintigraphy. Methods: Wister rats (n=10) were anesthetized with pentobarbital (50 mg/kg, i.p.) and the right maxilla teeth were extracted. An experimental denture, which covered the residual ridge at extracted sight, was inserted at 4 weeks after the extraction in 5 rats (denture-group). The preliminary study revealed that bone metabolism at the extracted sight was returned to the same level as the contralateral intact sight at 3weeks after the extraction. Other rats were fed without the denture (control-group). To observe the bone metabolic activity, bone scintigraphy of rat cranium was taken using a gamma-camera (Siemens ZLC7500) with a modified high-resolution pinhole collimator. 99mTc-MDP (2 mCi/rat) was injected intravenously. Static planer acquisition in coronal plane was executed at 2 hours later after the injection. The image takings were made at 4 days, 1 week, 2 weeks and 3 weeks after the denture insertion in denture-group and at the same interval in control-group. Accumulation of 99mTc-MDP to the alveolar bone at extracted sight and the contralateral intact sight were counted. Uptake ratio at the alveolar bone at extracted sight to the intact sight in denture-group and control-group were calculated. Results: The accumulation counts at the extracted sight were significantly higher than the intact sight at 4 days, 1 week and 2 weeks after the denture insertion in denture-group (Mann-Whitney U test, p<0.01), whereas there was no significant difference in control-group. The uptake ratio at extracted sight to the intact sight in denture-group was significantly higher than control-group (Mann-Whitney U test, p<0.01). Conclusions: These results elucidate that the denture wearing increased the turn over of alveolar bone under the denture base.

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