A clinical investigation of the morphological changes in the posterior mandible when implant-retained overdentures are used

Objectives: The widespread use and broad acceptance of osseointegrated dental implants as a means of retaining and supporting mandibular overdentures provide potentially stable three-dimensional reference structures, which have been used to examine the morphological changes of the surface contours of the mandibular ridges distal to implants. Unlike traditional methods that tended to measure changes in ridge morphology and quantity radiographically, this prospective study investigated the changes in the sagittal surface contours of the posterior residual ridges over a 1-year period by an alternative, non-radiographic method using serial casts of residual ridges of a group of patients. Material and methods: The residual ridges of the serial casts produced were examined using a profiling apparatus and computer software programs that allowed the orientation, digitised recording and measurement of the sagittal surface contours of the posterior residual ridges of mandibular casts in terms of area (cm(2)). Results: Statistical analysis revealed that the detected reductive changes in the surface contour of the posterior residual ridges following the wearing of an implant-retained mandibular overdenture over a 1-year period were highly significant (P<0.001). Conclusion: It is concluded that the methodology presented in this study can be used reliably as an alternative to radiographical examination for detecting changes that occur in the distal residual alveolar ridges of the implant containing edentulous mandible when implant-retained overdentures are used. Thus, the method presented may be used to contribute to a reduced exposure to ionising radiation for patients wearing implant-retained overdentures.