Biomedical Engineering Reference
In-Depth Information
Fig. 3.22
Profi les of wear
marks [
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
Table 3.3
Hardness and wear depth of occlusal surfaces of human teeth and one-way ANOVA
result
Primary
teeth
Permanent teeth
of young age
Permanent teeth
of middle age
Permanent
teeth of old age F
Sample
P
Hardness/HV
50g
313.4 ± 18.4 341.2 ± 11.7
360.0 ± 12.9
317.8 ± 15.4
21.51 <0.001
Wear depth/
μ
m
26.42 ± 1.94 18.34 ± 1.46
16.38 ± 1.31
23.12 ± 1.85
75.16 <0.001
Source
: From Zheng and Zhou [
42
]
types of teeth is less than 8 %. One-way ANOVA revealed signifi cant differences not
only between the hardness values, but also between the wear depths of the occlusal
surface for human teeth at different ages (
P
< 0.001). We also noted that the hardness
of the primary teeth was lower than that of the permanent teeth. Additionally, the
permanent teeth at the young and middle ages showed higher microhardness values
on their occlusal surfaces than those of the old age, and even harder than primary
teeth. Moreover, the wear depth was bigger for the primary teeth and for the perma-
nent teeth of the 55-year-old than that of the permanent teeth at the young and mid-
dle ages. Therefore, it could be inferred that wear resistance is weaker for the
primary teeth and permanent teeth of the old age than that of the permanent teeth at
the young and middle ages. As a result, an obvious fl uctuation in the friction coef-
fi cient at the later friction stage (Fig.
3.20
) and an uneven wear surface (Figs.
3.21
and
3.22
) are observed for the primary teeth and for the permanent teeth of the
55-year-old.
Figure
3.23
gives the relationship between the hardness-depth of the wear scar
and tooth ages. The wear depth decreased with increasing hardness, and the
