The Reason why a Sheath Exists in Enamel

Abstract

The stress of prism rods in enamel is reduced by the existence of sheaths. A finite element model including prism rods and sheaths was created, and we found that the sheath effectively reduces the stress concentration of the prism rods under both transverse loading (x-loading) and shear loading (zx-loading). In addition, the smaller the elastic modulus of the sheath, the larger the reduction in stress concentration. We believe this is why sheaths exist in enamel, although they are very small.