Biomedical Engineering Reference
In-Depth Information
Fig. 4.1
Variation in the
coeffi cient of friction as a
function of the number of
cycles in dry condition (vs.
52100 steel ball) [
28
]
Fig. 4.2
Variation in the
coeffi cient of friction as a
function of the number of
cycles under artifi cial saliva
condition (vs. 52100 steel
ball) [
28
]
under an optical microscope. In addition, some red oxidized debris detached from
the 52100 steel surface was obtained. The coeffi cient of friction slightly diminished
(D-E) due to the accommodation of the important third body [
29
].
Figure
4.2
gives the typical variation in the friction coeffi cient with the number of
cycles under artifi cial saliva condition. Compared to that in dry condition, some dif-
ferences in wear behavior existed in the artifi cial saliva condition. The friction coef-
fi cient was slightly lower (0.2) due to the lubrication effect at the early stage, but the
period with a lower coeffi cient was shorter in artifi cial saliva condition. In addition,
the coeffi cient varied between 0.9 and 1.1 after 100 cycles and appeared to be more
stable. After the test, dental tissue was less burned and carbonized. This means that
artifi cial saliva plays the role not only of a lubricant, like water, but also as a coolant.
Profi le measurement showed that the depth of the wear mark and its area were much
smaller under artifi cial saliva condition than under dry condition, as shown in Fig.
4.3
.
One of the effects of the saliva is lubrication. Human teeth are effectively
protected due to saliva lubrication during masticatory motion in the mouth. This is
why rapid wear at the teeth surface will occur in the absence of saliva, such as xero-
stomia, saliva gland tumor, and irradiation therapy. The burned appearance of the
