[Spatial variations of the mechanical properties of dental enamel and dentin]

Cuts with a Vickers diamond were made in five horizontal planes of the upper third of the crown of human lower premolars. At the same time the depth of entry was registered directly during the cutting with adot screen with a distance of about 150 mu between the dots. The depth of the cuts obtained was determined by optical measurement of breadth. Only in the fissure enamel was a slight hardening in the cervical direction observed. With a 5 p loading of the cutter diamond the reversible (elastic) deformation in the dentine is 0,4 +/- 0,1 micrometer greater than in the enamel. The optically determined cutting depth (irreversible deformation) amounted to 1,2 +/- 0,1 micrometer or 2,1 +/- 0,2 micrometer in enamel and dentine.