Biomechanics of the tooth cervical region investigated using 3D digital image correlation, micro CT, and finite element analysis

The cervical region of the tooth is a mechanically vulnerable transition zone that transmits occlusal loads from the crown to the root and constitutes a common site of clinical conditions, including dentin hypersensitivity and non-carious cervical lesions (NCCLs). However, the spatial distribution of stresses and strains induced by physiological and off-axis occlusal loading in this region, and their relationship to surface and subsurface damage, remain insufficiently characterized. Here, we investigated cervical tooth biomechanics under controlled axial and oblique loading. Ten extracted mandibular premolars were loaded quasi-statically up to 200 N at 0^ (axial) and 135^ (oblique) relative to the tooth long axis. Cervical biomechanics were characterized using two synchronized three-dimensional digital image correlation (3D-DIC) systems to map principal strains on the buccal and lingual surfaces, and high-resolution micro-computed tomography (micro-CT) scans acquired before and after loading to detect internal structural changes. A finite element analysis (FEA) model derived from the pre-loading micro-CT data replicated the experimental geometry and boundary conditions to quantify internal stress-strain fields. Strain-force ratios (strain per unit force) were higher under oblique than axial loading for dentin (buccal, p < 0. 01; lingual, p < 0. 001) and lingual enamel (p < 0. 05) ; under oblique loading, compressive strain magnitudes exceeded tensile magnitudes in enamel (p < 0. 05) and dentin (p < 0. 001). Oblique loading generated localized cervical strain concentrations in dentin, whereas axial loading produced more spatially uniform strain fields. The FEA results are consistent with these experimental patterns and predicted subsurface strain concentration within coronal dentin. Post-loading micro-CT revealed vertical mesiodistal cracks confined to coronal dentin, suggesting that subsurface microdamage can occur in the absence of clinically apparent surface failure. These findings emphasize the clinical importance of limiting eccentric loading; clinical interventions that reduce such forces may help mitigate the progression of subsurface microdamage and should be considered within comprehensive preventive care.