|Budget Amount *help
¥2,800,000 (Direct Cost : ¥2,800,000)
Fiscal Year 1998 : ¥500,000 (Direct Cost : ¥500,000)
Fiscal Year 1997 : ¥2,300,000 (Direct Cost : ¥2,300,000)
Strain data in superstructure and neck of titanium implant, which was a 3 times magnification model) were recorded, when a steel ball was dropped on the titanium implant from 10 cm height. Finite element analysis was done and strain data in same parts were gotten. The comparison between experimental data and theoretical ones could suggest appropriate analysis.
Next, finite element model was created, which expressed titanium implant in the mandibular bone. Steel ball was dropped on the porcelain of the superstructure, equivalent stress data in the porcelain and in the bone were compared. Parametric studies were done in this FE model. Parameters were as follows, 1)Implant material, 2)cancellous bone quality, 3)soft tissue around implant, 4)cement layer.
1)Implant material : There was no difference of the stress value in the porcelain among titanium, hydroxyapatite, steel. In case of dentin implant, 7% decrease in the stress value in the bone was found. 2)Higher the elastic modulus of cancellous bone becomes , greater the stress in the porcelain becomes and smaller the stress in the bone becomes. 3)When a soft tissue exists around implant, both the stress in the porcelain and bone become small. 4)Thicker the cement layer becomes. smaller the stress in the porcelain. But the stress in the bone was unchanged.
The above suggests that the stress in the porcelain as the superstructure worn on the osseointegrated implant may be greater than in the porcelain worn on the natural tooth.