Effect of age on the friction and wear behaviors of human teeth

Friction and wear behavior of human teeth at different ages against titanium alloy have been investigated using a reciprocating apparatus containing an artificial saliva solution. Human teeth at different ages of 8, 18, 35 and 55 years old were selected for tests. Both hardness and distribution of enamel rods on the occlusal surface, two of factors most important to tribological behavior of human teeth, are close to the age of teeth. It is found that not only the evolution of friction coefficient but also the wear behavior changes between teeth of different ages. Delamination and ploughing mechanisms are dominant for wear of human teeth, and more severe wear is observed for the primary and the permanent teeth at the old age accompanied by remarkable fluctuation in the friction coefficient. Compared with the primary teeth and the permanent teeth at the old age, the permanent teeth at the young and middle ages have better wear-resistance.