インプラントオーバーデンチャー用磁性アタッチメントの最適上面形態のバイオメカニックス解析

抄録

The use of magnetic attachments in implant-supported overdentures has been attempted in a variety of forms. Magnetic attachments for two implants inserted in the canines area between both mentale foramen in the edentulous mandible in particular are highly regarded for their simplicity and usefulness. Nevertheless, the distribution of force acting on the residual ridge differs depending on the shape of the upper surface and has yet to be clarified.
To clarify the optimal shape of the upper surface for attachment, we geometrically analyzed the compression force acting on the residual ridge, bearing capacity of the residual ridge, and the effects of two types of upper surfaces, a dome shape and a reverse dome shape. We inserted an implant fixture in the portion corresponding to the canines between both foramen mentale in a standard model of the edentulous mandible and attached a dome attachment. We fabricated a plaster model and measured the slope and area of the residual ridge. In accordance with Young's modules, we calculated the compression force on the residual ridge mucosa by the denture with respect to a fixed amount of sinking and determined the ratio of the supportable occlusal force as support efficiency.
In addition, symmetrical to the dome shape, a reverse dome shape with the same radius of curvature was analyzed in a similar manner.
As a result, the dome shape was able to support occlusal force 10.7% greater than the reverse dome shape at a fixed amount of sinking. With respect to fixed occlusal force, the dome shape had 11.1% less sinking of the residual ridge mucosa than the reverse dome shape. In addition, the dome shape displayed maximum support efficiency at the portion distal to the first molar, and support capacity was evenly distributed. In contrast, the reverse dome shape displayed maximum support efficiency at the portion corresponding to the second premolar, and the range of support efficiency tended to be concentrated.
These results suggest that the dome shape is superior to the reverse dome shape by effectively and evenly bearing a large occlusal force on the residual ridge mucosa.