Comparative finite element analysis of external and internal hex connections in mandibular All-on-4 implants under axial loading
DOI:
https://doi.org/10.3329/bjms.v25i10.86637Keywords:
All-on-4 implants, finite element analysis (FEA), implant– abutment connection, stress distribution, hex connectionaAbstract
Background The biomechanical performance of implant–abutment connection designs plays a crucial role in the long-term success of all-on-4 implant-supported prostheses. External hex connections (EHCs) and internal hex connections (IHCs) differ in geometry, load transfer, and mechanical stability, which may influence stress distribution and the likelihood of mechanical complications. Materials and Methods A three-dimensional finite element model of a mandible with an all-on-4 implant configuration was developed. Two connection designs—EHC and IHC—were simulated with identical implant positioning and prosthetic frameworks. A static axial load was applied to the distal cantilever region. Stress distribution was analyzed in key components including prosthetic screws, multi-unit abutments (MUAs), implant screws, and fixtures. Peak von Mises stress values were compared between the two connection groups. Results Both EHC and IHC configurations demonstrated biomechanical stability under axial loading. In both groups, the highest stress concentrations were observed in the prosthetic screws, followed by MUAs, indicating potential weak points in the posterior implants. The EHC group exhibited significantly lower peak stresses in critical components: the implant screw showed 37.75% lower stress and the implant fixture showed 33.03% lower stress compared to the IHC group. Overall, EHCs demonstrated more favorable stress distribution characteristics. Conclusion: External hex connections may offer biomechanical advantages over internal hex designs in all-on-4 mandibular prostheses by reducing stress transmission to implant screws and fixtures. Although both connection types performed within clinically acceptable limits, the reduced stress in the EHC group highlights its potential to minimize mechanical complications. Further experimental and clinical studies are recommended to validate these findings and support optimization of implant–abutment connection designs for full-arch restorations.
Bangladesh Journal of Medical Science Vol. 25. Supplementary Issue 2026, Page : S146-S153
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Copyright (c) 2026 R Padmini Rani, Aswini Kumar Kar, Purna Chandra Mishra
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