Strain 3D-FEA in restorations supported by tilted vs axial implants

Objectives: This 3D-FEA aimed at evaluating the biomechanical response of bone and implant-supported prostheses in the presence of axial and tilted implants. Methods: Four numerical models of human mandible with different implant-supported prostheses configurations were set up. The cortical bone was considered orthotropic according to an indipendent mechanical characterization performed on fresh human dentate mandibles. Jaw-closing muscular forces were simulated. The spongy bone was considered isotropic while the temporo-mandibular disc was considered hyperelastic. Contact pairs elements were generated at the fixture-bone interfaces. Failure criteria were based on ultimate normal and shear stresses computed in in vivo. The strain fields in the periimplant bone were compared to Frost's biomechanical relation. The bone remodelling stimuli were computed as the strain energy density variations. Results: EPTO1=FIRST PRINCIPAL STRAIN EPTO3=THIRD PRINCIPAL STRAIN STRAIGHT IMPLANTS. PERI-IMPLANT STRAIN FIELDS. POSTERIOR IMPLANTS, EPTO1 2000 TO 8000, EPTO3 -1500 TO -8000. ANTERIOR IMPLANT, EPTO1 667 TO 4667, EPTO3 -667 TO -3340. STRAIN STATE ON EXTERIOR CORTEX BETWEEN IMPLANTS, EPTO1 100 TO 1000, EPTO 3 -100 TO -1000. STRAIN STATE IN SPONGY BONE BETWEEN IMPLANTS, EPTO1 100 TO 500, EPTO3 -100 TO -500. TILTED IMPLANTS. PERI-IMPLANT STRAIN FIELDS. POSTERIOR IMPLANTS, EPTO1 333 TO 4330, EPTO3 -667 TO -3333. ANTERIOR IMPLANT, COMPARABLE TO STRAIGHT CONFIGURATION. STRAIN STATE ON EXTERIOR CORTEX BETWEEN IMPLANTS, COMPARALE TO STREISHT CONFIGURATION. STRAIN STATE IN SPONGY BONE BETWEEN IMPLANTS, COMPARABLE TO STRAIGHT CONFIGURATION. Conclusions: Bone strain fields were scarcely influenced by implant orientation but significantly influenced by the rigidity of the restorative material.