Biomedical Engineering Reference
In-Depth Information
Chapter 3
Friction and Wear Behavior of Human Teeth
3.1
Introduction
This chapter deals with the friction and wear behavior of human teeth. Human teeth
are the important masticatory organ in body. In general, oral biomechanical func-
tions can result in tribological movement of teeth occurring in the mouth [
1
-
4
].
Hence, tooth wear is a cumulative multifactorial lifetime process, which to a large
extent is irreversible [
5
,
6
]. However, excessive wear may lead to a lack of perfect
occlusal contact (the contact related to occlusions of the teeth, especially on the
chewing or biting surfaces), a lower mastication effi ciency, and an obliteration of
the chewing surface [
7
-
12
]. Understanding the friction and wear behavior of human
teeth would help deepen the scientifi c knowledge about human teeth and then pro-
vide valuable insights into the development of advanced dental materials, oral treat-
ments, as well as the biomimetic design of an antiwear engineering system based on
human teeth.
Human teeth possess a unique structure composed of enamel, dentin-enamel
junction (DEJ), dentin, and pulp; each zone is anisotropic due to the enamel rods'
orientation, dentinal tubule, etc. [
13
]. Enamel is the hardest tissue in the human
body because of the existence of enamel rods and is a composite consisting of both
a mineral phase and an organic phase. Compared with enamel, dentin is widely
considered to be elastic and soft. The study of Xu et al. indicated that microcracks
formed on enamel interact with the DEJ and the enamel rods strongly and that the
mechanical properties of teeth are functions of microstructural orientations [
14
].
The mechanical properties, chemistry, and microstructure of enamel in a maxillary
second molar (M
2
) have been characterized as a function of location on an axial
cross section [
15
]. Based on the previous results, it is reasonable to deduce that the
tribological behavior of human teeth also interacts strongly with the microstruc-
ture's orientation and location.
Wear of human teeth is an extremely complex process that involves mechanical,
thermal, and chemical reactions. The wear rate of teeth may be closely associated
with human physiological factors (such as age, gender, etc.) and pathological
