<![CDATA[Physiological variability in bone mechanical properties may affect load transfer and biomechanical stability in dental implant systems. However, the influence of orthotropic elastic and shear properties on implant–bone biomechanics remains unclear. This study evaluated the sensitivity and robustness of a mandibular first molar implant system to variations in orthotropic bone properties using finite element analysis. A three-dimensional implant–bone model was analyzed under nine material configurations, including gradual orthotropic variations (±15% of baseline) and independent modifications of the elastic and shear modulus. Biomechanical responses were evaluated using von Mises stress, principal stresses, strains, and displacements. Stress concentrations were primarily located at the implant–abutment connection and crestal cortical bone, indicating the main load-transfer pathways. Increasing directional stiffness reduced peri-implant strain and displacement but increased cortical stress, revealing a trade-off between deformation reduction and local stress concentration. Elastic modulus predominantly influenced global stress redistribution, whereas shear modulus had a greater effect on local deformation and peri-implant stability. Strain and displacement were more sensitive to material variations than stress-based parameters. These findings emphasize the importance of orthotropic material representation for realistic biomechanical assessment of dental implant systems under physiological variations in bone quality.]]>
