Minimum Number of Implants for Occlusal Support in Edentulous Mandible

Minimum Number of Implants for Occlusal Support in Edentulous Mandible
H. YAMAMOTO, Y. MAEDA, M. SOGO, and S. MURAKAMI, Osaka University, Japan
March 2004
Clinical Implant Studies
Objectives: The objective of our study was to find out the minimum number of implants and their location to restore the occlusal support in edentulous patients. In this study, a three dimensional finite element edentulous mandible model was made to analyze the influence of the number and location of implants on the stress distributions.
Methods: CT scan and special software obtained geometric data of edentulous dry skull mandible along with bone density. A three dimensional finite element model was created with these data. We applied the compact bone material properties to the element with higher bone density to recreate the 3 dimensional inside structure of the mandible. Fourteen fixation points simulating occlusal stop by implants were assigned on the residual ridge crest where natural teeth supposed to be anatomically. Muscle forces were applied as vectors according to Nelson report (1986). Validation of the 3D model was conducted by the strain measurement with 40 strain gauges on the dry skull under same loading conditions as the 3D model.
Results: Four implants where two implants in canine region and two implants in second molar region showed the similar pattern of stress distribution as 14 implants where occlusal support was fully restored by implants. Six implants in anterior region showed higher stress concentration in the mandible angle area than those of 14 or 4 implants. The same trend was also found in the strain measurements on the dry skull.
Conclusions: Within the limitation of the simulation, we concluded that we could restore the occlusal support at least with four implants if we place them in the proper location in edentulous mandible.