Thesis (M.Sc.) - Cairo University - Faculty of Oral and Dental Medicine - Department of Prosthodontics

Objectives: To analyze the stresses induced in the mandibular bone supporting a four implant-retained complete overdenture. Completely and partially implant-connected rigid bars were studied under flexure load. Materials and methods: A software program was used to simulate four numerical models of an edentulous mandible and a prosthetic situation containing four implants. In each two models with similar implant sites, the superstructure was once rigidly connected to the posterior implants and was once only supported by the posterior implants. The models were meshed with a fine solid mesh and the analysis was conducted with the iteration method. The stresses were recorded at different zones of the peri-implant bone and the micro-strains in the prosthesis were also obtained. Results: In M1 and M3 the stresses at the peri-implant bone of the posterior implants are approximately 50% higher than the anterior implants and are slightly lower than the anterior implants in M2 and M4.The highest micro-strain value in the denture was found in M3 followed by M1, M2 and finally M4. Conclusion: The maximum displacement was reported at the condylar neck followed by the retromolar region and the least values were reported at the symphysis. Placement of implants in a more posterior position limits the mandibular flexure, however stresses at the peri-implant bone become relatively higher. Complete connection of rigid bars between the anterior and posterior implants also limits the mandibular flexure but also shows higher stress values at the peri-implant bone relative to the partially connected bar

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