Influence of abutment diameter for platform switching on the biomechanics of internal and external hexagon posterior implants

Objective: The aim of this study was to evaluate the influence of the reduction of abutment's diameter for platform switching on stress distribution of single implant with external or internal connections using three-dimensional (3D) finite element analysis. Materials and Methods: A total of 8 virtual 3D models were constructed containing one single implant (5.0 × 11.0 mm) in a mandibular segment supporting a single first molar screwed crown. The implants presented external or internal hexagon connections with UCLA abutment with different diameters: 3.8, 4.2, 4.6 or 5.0 mm. All structures were considered perfectly bonded and each model received a 200 N oblique load on the occlusal surface distributed on 8 points. The maximum tensilestress (σmax) and the maximum principal elastic strain (ℇmax) were calculated for the cortical and trabecular bones and equivalent Von Misses (σvM) for dental implant and abutment using ANSYS Workbench software. Results: The reduction of abutment diameter produced a reduction of stress values in bone tissue up to 3,6% in internal hexagon. On the other hand, the smallest abutment diameter for external hexagon connection produced the highest stress in surrounding cortical bone(53 MPa).The reduction of abutment diameter increased the stress and strain in both theabutment (up to 360%) and implant (up to 200%), regardless of implant connection. External hexagon connection presented the highest stress and strain magnitudes. Conclusion: The reduction of abutment diameter improves stress distribution in bone tissue, regardless of implant connection type. However, it increases the stresses within the implant and abutment, which could compromise their mechanical resistance.