The influence of implant location and length on stress distribution for three-unit implant-supported posterior cantilever fixed partial dentures

STATEMENT OF THE PROBLEM: The influence of implant location for an implant-supported cantilever fixed partial denture (FPD) on stress distribution in the bone has not been sufficiently assessed. PURPOSE: This study examined the influence of location and length of implants on stress distribution for 3-unit posterior FPDs in the posterior mandibular bone. MATERIAL AND METHODS: Each 3-D finite element model included an FPD, mesial and distal implants, and supporting bone. The mesial implant with a length of 10 mm or 12 mm was placed in locations where its long axis was 3 mm to 11 mm posterior to the remaining first premolar. The distal implant with a length of 10 mm was fixed at the same distance from the premolar on each model. A buccally-oriented oblique occlusal force of 100 N was placed on each occlusal surface of the FPD. RESULTS: The maximum equivalent stresses were shown at the cervical region in the cortical bone adjacent to the mesial or the distal implants. Relatively high stresses of up to 73 MPa were shown adjacent to the mesial implant located 9 mm or more posterior to the first premolar. The use of a 12-mm-long mesial implant demonstrated a relatively weak influence on stress reduction. CONCLUSION: The implant location in the cantilever FPDs was a significant factor influencing the stress created in the bone.