On the friction and wear behaviour of human tooth enamel and dentin

The differences in the friction and wear behaviour of different human tooth structures against titanium have been investigated using a reciprocating apparatus containing an artificial saliva solution. The effects of enamel, enamel rod orientation, and dentin were of particular interest. A normal load of 20 N, reciprocating amplitude of 500 μm, and frequency of 2 Hz were used. Tests lasting up to 5000 cycles were conducted. The micro-indentation hardness of worn teeth specimens was measured. The enamel layer exhibits relatively low friction and good wear resistance. The number of cycles of low friction coefficient, prior to transition to a higher value, depends on enamel thickness and enamel rod orientation. Wear mechanisms differ between layers in the tooth structure.