Biomedical Engineering Reference
In-Depth Information
400
40
Hardness
Depth
300
30
200
20
100
10
0
0
a
b
c
d
Fig. 3.23
Variations in the wear depth and hardness of teeth at four ages [
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 3.4
Comparison of the hardness and wear depth of human teeth by paired
t
-test (
P
< 0.005)
Permanent teeth
of young age
Permanent teeth
of middle age
Permanent
teeth of old age
Primary teeth
Sample
Hardness depth
Hardness depth
Hardness depth
Hardness depth
Primary teeth
−4.045
a
10.50
a
−6.578
a
13.56
a
−0.587
b
3.882
a
Permanent teeth
of young age
−4.045
a
10.50
a
−3.407
a
3.164
b
3.827
a
−6.411
a
Permanent teeth
of middle age
−6.578
a
13.56
a
−3.407
a
3.164
b
6.649
a
−9.421
a
Permanent teeth
of old age
−0.587
b
3.882
a
3.827
a
−6.411
a
6.649
a
−9.421
a
Source
: From Zheng and Zhou [
42
]
a
Signifi cant difference
b
Nonsignifi cant difference
permanent teeth at the young and middle ages had better wear resistance than teeth
of the old age. We also found that throughout their life, all permanent teeth showed
a better wear resistance than primary teeth.
Table
3.4
compares the hardness and wear depth of human teeth at different ages
by paired Tukey's test (
t
-test) analysis. Paired
t
-test analysis revealed signifi cant
differences between the hardness and no signifi cant differences between the wear
depth of permanent teeth at the young and middle ages (
P
< 0.005). This would
imply that microhardness is not the only infl uencing factor on the friction and wear
behavior of human teeth.
