Evaluation of prosthetic structures and mandibular tissues on total and partial edentulous patient treated with tooth, implant and implant-tooth supported removable overdenture prosthesis, by three dimensional finite element analysis

The aim of this study is to evaluate the biomechanical behavior of trabecular and cortical bone, denture, dentin, implant, periodontal ligament, and retentive elements on tooth, implant and implant-tooth supported removable overdenture prosthesis by three dimensional finite element analysis.Four different designs were constructed in 3 dimensional edentulous mandibular model. In the first design, two canine teeth; in the second design, two implants on canine tooth region; in the third design, two canine teeth and two implants on second molar region and in the fourth design, two implants each with locator retentive on canine and second molar region were used as mandibular removable overdenture prosthesis support. Loading was applied vertically on left canine, premolar and molar teeth with a total of 100 N. Designs 3 and 4 showed lower displacement and low contact pressure and compressive stresses at mucosa when compared with model 1 and 2 on finite element analysis. Cortical bone around posterior implants, locator abutment, locator matris and housing at unloaded posterior implant sites showed higher stresses in design 4. Stress values of periodontal ligament and dentin was decreased with the placement of implant at posterior region in model 3. With the placement of implant at posterior region, the strain values were increased on trabecular bone in second molar region.The highest stresses that occur on cortical bone around the posterior implant were lower than the highest values indicated to cause bone resorption. The results showed that strain values occurred on edentulous posterior alveoler ridge were close to the lowest values of numerical analyses of stimulus window scale defined for bone apposition and resorption by Frost; with placement of implant to posterior region strain values were increased in this bone region and all strain values were grouped in Frost?s stimulus window scale. The highest stress values were obtained on posterior implant, locator, matris and housing in design where four implants were used. The stress values were below materials endurance limit. However, effects of obtained stress and strain values on bone resorption and locator retention should be evaluated with long term clinical studies.