<![CDATA[Composite resin restorations frequently fail due to secondary caries formation. To address this, the antibacterial potential of chitosan for incorporation into dental composites has been explored. Given the limitations of existing studies—which often lack a focus on biomechanical function, this research used an in silico Finite Element Analysis (FEA) to evaluate the combined effects of chitosan addition and cavity dimension on stress and strain distributions within restorative materials. A 3D model of a human mandibular first molar, derived from micro-CT scanning, was subjected to FEA using varying chitosan concentrations (0%, 0.5%, 1.0%, and 2.0%) and two cavity dimensions (conservative and extensive). Statistical results showed significant differences in stress and strain distributions across the treatment groups. Cavity dimensions significantly influence the distribution of stress and strain. The effect of chitosan addition is secondary. The addition of chitosan in cases of extensive cavities was not strong enough to produce statistically significant changes. The FEA analysis demonstrates a clear influence of cavity geometry on biomechanics: In extensive cavities, the restorative material provides superior structural reinforcement, leading to a stiffer composite unit (high stress, low strain) and limited cusp deformation; while in conservative cavities, the structure exhibits a highly flexible response to loading (low stress, high strain), even with a preserved marginal ridge. The stress concentration in the tooth model was primarily in the cervical area, specifically at the cementoenamel junction (CEJ).]]>
