Effect of void formation on polymerized shrinkage in dental resin composite using finite element approach

Resin-based dental composites are widely used in modern dentistry due to their esthetic properties, adhesive capability, and conservative preparation requirements. However, their long-term success is threatened by two persistent challenges: polymerisation shrinkage and void formation. Polymerisation shrinkage, typically ranging from 1.5% to 5%, generates internal stress at the tooth–restoration interface, leading to marginal gaps, microleakage, postoperative sensitivity, and eventual restoration failure, while voids introduced during clinical placement or material handling act as stress concentrators that weaken the restoration and increase probality to fracture, debonding, and bacterial infiltration. Although shrinkage behavior has been extensively studied, limited attention has been given to the combined influence of void size and location on the biomechanical integrity of composite restorations. This study addresses the gap by employing a hybrid experimental–computational approach in which a human molar tooth was reconstructed into a three-dimensional Class I cavity model using highresolution micro-computed tomography (micro-CT), restored with a bulk-fill resin composite (3M ESPE), and simulated with finite element models of void-free and voided composites containing spherical voids of 1 mm and 2 mm placed at the centre, side, and margin of the cavity. Experimental micro-CT analysis provided validation of polymerisation shrinkage, which was then correlated with finite element analysis (FEA) simulations of volumetric contraction, linear displacement, and stress distribution under curing and simulated occlusal loading of 120 N. Results showed strong agreement between micro-CT and FEA, with deviations within the accepted tolerance of 10%, confirming the robustness of the computational model. Voids were found to significantly alter stress distribution, with larger and marginally located voids producing higher tensile stress concentrations and greater displacement at critical regions, whereas central voids exerted minimal influence. By integrating validated FEA with experimental characterisation, this study advances understanding of the mechanical consequences of voids in resin composites and underscores the importance of minimising void formation while providing clinically relevant guidelines for recognising surface displacement patterns associated with internal voids, ultimately contributing to more durable and reliable restorative outcomes.