On edge chipping in molar teeth from blunt occlusal contact

Edge chipping is a leading failure mode in dental teeth. Virtually all chipping studies are limited to Vickers indentation on polished cusps of molar teeth. Such works are here extended to spherical contact. Occlusal loads are applied on the tooth's central fossa or a polished cusp using ball radii ranging from 0.4 to 5.16 mm. The chip dimensions are characterized by h/D_m and D/D_m, where h, D and D_m denote indent distance, chip size and tooth crown diameter. For the fossa loading, h/D_m, D/D_m and the least chipping force P_ch are virtually independent of ball radius r for r < ≈ 4 mm. In this range, h/D_m and D/D_m lie between ≈0.30 to 0.36 and 0.51 to 0.69, respectively, while P_ch equals ≈1330 N. For r > ≈ 4 mm, the failure occurs by debonding of enamel sectors from the dentin core. In the case of cusp loading, h/D_m < ≈ 0.3 while D/D_m and P_ch vary with r. For relatively small h or large r, the failure occurs as soon as radial cracks initiate under the loading point. For a load applied near a cusp tip, the failure occurs by enamel debonding. Finally, the present work is easily extendable to fossil teeth of hominins and apes as well as prosthetic teeth. The morphological features obtained in such studies should provide quantitative means to assess the relationships between chip dimensions, chipping force and diet characteristics.