Biomedical Engineering Reference
In-Depth Information
Fig. 3.21
Wear mark observation subjected to 5,000 cycles [
42
]: (
a
) primary tooth; (
b
) permanent
tooth of the young age; (
c
) permanent tooth of the middle age; (
d
) permanent tooth of the old age
effect on wear behavior. As seen in Fig.
3.21d
, some bigger pits and more ploughing
traces appeared on the worn surface of the permanent teeth of the 55-year-old in
comparison with the permanent teeth of the young and middle ages (Fig.
3.21b, c
).
More detailed changes in the wear behavior could be seen under higher magnifi ca-
tion (see the inserts). The enamel rods on the worn surfaces were relatively intact for
the permanent teeth at both the young and middle ages, while the enamel rods on the
worn surfaces showed severe plastic deformation both for the primary teeth and for
the permanent teeth of the 55-year-old. Further profi le measurements on the wear
marks of each group showed that rougher profi les of the wear scar with an average
maximum wear depth of 27 and 23
m for the primary teeth and the permanent teeth
of the 55-year-old, respectively, occurred, which were deeper than those of the per-
manent teeth of the young and middle ages (18 and 16
μ
m). Typical wear profi les
for each group are shown in Fig.
3.22
. Some fl uctuations corresponding to an
uneven wear surface were noticed in the profi le lines of the primary teeth and the
permanent teeth of the 55-year-old.
The mean values of microhardness (
H
) and wear depth of the occlusal surface for
human teeth at different ages with their standard deviations and one-way analysis of
variance (ANOVA) result are shown in Table
3.3
. The standard deviation for the four
μ
