Digital moiré interferometric investigations on the deformation gradients of enamel and dentine: An insight into non-carious cervical lesions

Objectives The objective of this study was to evaluate the biomechanical basis of non-carious cervical lesions by examining the patterns of deformation (strain) in the enamel and dentine. Methods The digital moiré interferometry is optics based non-destructive, whole-field experimental technique that provides whole-field strain information. Diffraction gratings (with a frequency of 1200 lines/mm) were transferred onto sagittal sections of human teeth, which were subsequently loaded compressively for loads ranging from 10 to 200 N at the incisal edge of the tooth. The acquired digital moiré fringe patterns were used to determine the in-plane deformation pattern in the enamel and the dentine in the direction parallel to the long axis (axial direction) and in the direction perpendicular to the long axis (lateral direction) of the tooth. Results It is observed that the enamel displayed marked strain gradients in the lateral direction, while the coronal dentine experienced marked strain gradients in the axial directions during compression. With the increase in applied loads, the strains in the enamel increased at the cervical edge (above the cemento-enamel junction) on the facial side, while the strains in the dentine increased below the cemento-enamel junction on the facial side. Conclusion The enamel and dentine displayed unique in-plane deformation patterns in the axial and the lateral directions of the tooth. These experiments support the hypothesis that occlusal loading will contribute to cervical loss of dental hard tissues.