Abstract: Objective: To study the influence of the varying inclination angles of distal implants and cantilever lengths of All-on-4 denture on stress distribution of implants and peri-implant bone tissues at different bone densities and to provide evidence for clinical applications. Methods: An edentulous mandible was scanned by CBCT. The DICOM digital images were obtained from CBCT and imported into Mimics for 3D-reconstruction. Geomagic studio was used to transfer the numerical model to entity. Unigraphics and ANSYS Workbench were deployed to found the three-dimensional finite element model simulating All-on-4 denture. When the lengths of prosthetic arcs were equal, models were modified in inclination of distal implants and cantilever lengths under Type Ⅱ and Type Ⅲ bone conditions. Static vertical forces of 150N were applied to the bilateral distal ends of each cantilever to analyze the stress distribution on implants and bone tissues nearby. Results: When angles of inclination were set 30°, 45°and 60°, the corresponding cantilever lengths were 10.8mm, 8mm and 6.3mm. The maximum stress values in Type Ⅱ bone condition were 26.8MPa, 23.5MPa and 16.3MPa and those in Type Ⅲ were 40MPa, 29MPa and 21.8MPa. Conclusion: The lower the bone density, the greater the stress values in peri-implant cortical bone. When the lengths of dental arcs were equal, an increase in angles of inclination with the successive decrease in cantilever lengths could effectively diminish the stresses in peri-implant bone tissues.

Key words: All-on-4 , Bone density, Stress analysis, Three-dimensional finite element