Fixture design effects on posterior dental implant stability using finite element analysis (FEA): a systematic review.

Tooth loss is prevalent in the posterior region, and dental implants require optimized fixture design to ensure biomechanical stability, which is often the approach using finite element analysis (FEA). This systematic review, using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guidelines in its writing, aimed to assess the influence of fixture design on posterior implant biomechanical stability, such as stress and strain, by FEA analysis. The study search used PubMed, ScienceDirect, MDPI, SpringerLink, and OpenAire databases to find studies that analyzed fixture level, body shape, thread characteristics, diameter, length, and neck model, covering studies published between 2020 and 12 January 2025. Data from 39 of the 3,562 studies were synthesized narratively, guided by SWiM, and grouped by design parameters, with bias assessed using ROBFEAD. Tissue-level fixtures outperformed bone-level fixtures in reducing cortical bone stress and improving fatigue resistance, while the tapered body shape increased stress distribution in low-density bone (D4). Square threads minimize micro stress and movement, and larger diameters and lengths increase stability, although excessive dimensions increase cortical stress. The micro-thread neck design reduces bone resorption. The high risk of bias resulting from the lack of mechanical validation, isotropic assumptions, and static loading conditions requires attention when interpreting research findings. Clinical or experimental validation is required. Future studies should standardize thread reporting, use computed tomography (CT)-based modeling, and simulate dynamic loading for patient-specific designs.