Biomechanical evaluation of narrow-diameter Ti-Zr implant systems at different lingual inclination angles in the...

Narrow-diameter implants may be considered in posterior sites with limited bone volume, while lingual inclination may help avoid anatomical constraints. However, their biomechanical behavior under different loading directions remains unclear.

To compare the system-level biomechanical responses of a 3.3 × 12 mm titanium-zirconium implant configuration and a 4.1 × 10 mm commercially pure titanium implant configuration at different lingual inclination angles.

Three-dimensional finite element models were constructed for both implant systems at 0°, 5°, 10°, 15°, and 20°. A 150 N vertical load and a 150 N load applied at 30° to the prosthetic crown axis were simulated. Implant von Mises stress and cortical and cancellous bone maximum principal stress were evaluated. Formal mesh convergence analysis was performed using three mesh densities. Exploratory fatigue analysis and in vitro displacement testing were conducted under vertical loading.

Mesh convergence showed less than 5% change between the medium and fine meshes for all primary stress outcomes. Under vertical loading, implant stress decreased from 0° to 10° and then showed modest fluctuations. Oblique loading increased implant and peri-implant bone stresses in all configurations, with generally greater amplification at larger inclination angles. Implant stress remained lower at 10° than at 0° under both loading conditions, whereas cortical bone stress increased across the same range. In vitro displacement remained relatively stable from 0° to 10° and increased at 15° and 20°.

Inclination-related responses depended on loading direction and the evaluated biomechanical outcome. The 0°-10° range should not be interpreted as uniformly favorable or clinically recommended. Because the systems differed in material, diameter, length, and geometry, the findings represent system-level comparisons.