抄録
A removable partial denture (RPD) is supported by residual teeth and edentulous alveolar ridge. To preserve the health of remaining oral structures and to restore their functions, the RPD must be designed to distribute retentive forces among the residual teeth and edentulous alveolar ridge properly.
However, previous designs do not seem to be able to yield the proper distribution of retentive forces,which leads to the irreversible changes of the retentive teeth and edentulous alveolar ridge. Especially, in the major edentulous cases like Eichner Class B-2 classified by Eichner method, the movement of the RPD is large in the edentulous areas, and the absorption of the edentulous alveolar ridge is aggravated.
Therefore, we planned an overdenture with osseointegrated implant fixed in edentulous areas, which is supposed to decrease the movement of the denture and to limit the absorption of the edentulous alveolar ridge. A two-dimensional finite element technique was used to analyze the implant overdenture (IOD) which was set on the edentulous alveolar ridge side.
The results obtained by the finite element analysis were as follows:
1. The values of the movement of the RPD were about four times larger than those of the IOD.
2. The von Mises stresses of the soft tissues in the edentulous areas of the RPD were about four times larger than those of the IOD.
3. The maximum principal stresses of the alveolar bone in the edentulous areas of the RPD were about four times larger than those of the IOD.
4. It is suggested that the clinical application of the overdenture with osseointegrated implant fixed in the edentulous areas is effective to decrease the movement of the overdenture and to limit the absorption of the edentulous alveolar ridge.
Based on this analysis, the IOD was clinically applied. The present clinical case confirms that the movement of the IOD is smaller and the IOD is more stable than the RPD and that the absorption of the residual alveolar bone has not occurred.
