On the deformation behavior of human dentin under compression and bending.

The cause of difference in deformation behavior of human dentin under compression and bending is discussed. Mechanical properties of dentin under these deformation schemes are compared. Microstructural study of fracture surfaces of samples and cracks in dentin is carried out, too. Dentin behaves like a brittle solid under bending, whereas it exhibits various types of response from brittle to highly deformable under compression that depended on the geometry of sample (d/h ratio of a cubic sample). It is shown that the quantity of cracks on the compressed sample increases when its elasticity and plasticity grow up, whereas under bending the failure of sample occurs due to the advancement of dominant crack. Deformation and crack growth are the channels for the accommodation of applied stress in dentin. Crack growth is the leading one when the level of tensile stress in sample is dominant, whereas deformation becomes the leading channel when compression stress is dominant. However, in both cases contribution of the concurrent channel cannot be ignored. This feature is caused by the ductile fracture mode of dentin on the mesoscopic level.