2003 年 16 巻 2 号 p. 214-225
Statement of problem: In order to improve denture stability, patient's satisfaction and longterm success of mandibular distal extension removable partial dentures, it seems to be effective to place an osseointegrated implant beneath the distal extension denture base for denture support. However, there is no scientific evidence which supports the biomechanical benefit of this system.
Purpose: This study investigated the effect of utilizing an osseointegrated implant as a distal support of a mandibular distal extension removable partial denture.
Material and method: The Kennedy class Ⅱ mandibular partially edentulous case was simulated. The missing teeth were the right side second premolar and molars in the mandible. An implant fixture (3 i OSSEOTITE, Implant Innovations, USA) was placed at the second molar region. Three types of prostheses were fabricated: a conventional distal extension removable partial denture without implant support (called PD model), an implant supported removable partial denture (called PDI model), and fixed partial denture using first premolar and the implant (called BR model). Strain gauges were attached to the surfaces of the abutment tooth and the implant. A vertical load of 100N was applied on each prosthesis at the second premolar, first molar and second molar region.The axial force and bending moment on the abutment tooth and the implant were measured. The disto-mesial displacement of the abutment tooth (first premolar) was measured using a CCD laser displacement sensor. The obtained data were statistically analyzed using two-way analysis of variance (p=0.05).
Results: The PD model showed the biggest vertical displacement of the prosthesis. The bending moment of the abutment tooth and the bending moment of the implant were the highest in the BR model, and were the lowest in the PDI model. Further, concerning the stress distribution of the implant, bending moment around the implant was not generated and the applied force was transmitted along the implant axis in the PDI model.
