The Influence of Medial Implant Location in the Three-unit Posterior Fixed Partial Dentures on Stress Distribution in the Surrounding Mandibular Bone

The Influence of Medial Implant Location in the Three-unit Posterior Fixed Partial Dentures on Stress Distribution in the Surrounding Mandibular Bone
26 June 2003
S. YOKOYAMA, N. WAKABAYASHI, M. SHIOTA, and T. OHYAMA, Tokyo Medical and Dental University, Japan
IADR
Objectives:This study examined the influence of medial implant location in the three-unit posterior fixed partial dentures (FPDs) supported by two implants on stress distribution in the madibular bone. Methods:A three dimensional finite element model included three-unit FPD, cortical and cancellous bone and two osseointegrated implants (4mm in diameter and 10mm or 12mm in length). Each models featured one of five different medial implant locations, between the missing second premolar and the first molar. The distal implant was fixed at the missing second molar location. Oblique bite force of 100N in 30 degrees buccal from the vertical direction was loaded on each of three artificial teeth, respectively and simultaneously, while the lower surface of the mandible was fixed. Results:The maximum equivalent stress in the cortical and cancellous bone generally increased as the medial implant shifted from a medial to a distal position. Under a single bite force on the second premolar in the models using the 10mm implants, relatively low maximum stresses within the cortical bone (22MPa to 25MPa) were shown in the models with the medial implants placed at a location that was one implant diameter distal from the most medial position, while higher maximum stresses (31MPa to 36MPa) were demonstrated in the models with the more distally placed medial implants. The maximum stresses in the 12mm medial implant models were lower than those with 10mm implants. However, the maximum stresses in models with the distally placed 12mm medial implants were not as low as those in the medially placed 10mm medial implants. Conclusions:The results suggest that reasonably low mechanical stress in the surrounding bone is assured when the medial implant is placed in the range between the missing second premolar position and one implant diameter distal from that location.