Biomedical Engineering Reference
In-Depth Information
Table 4.5
XRD patterns of crystals on different enamel surfaces
HA 01-074-0566
Original
Eroded
Remineralized
Sample
crystal
plane
Relative
intensity/% 2
Relative
intensity/% 2
Relative
intensity/% 2
Relative
intensity/%
2
θ
/°
θ
/°
θ
/°
θ
/°
(211)
31.766
100.0
/
/
/
/
31.688
100.0
(112)
32.195
51.5
32.164
100.0
32.180
100.0
32.256
60.6
(002)
25.883
35.7
25.865
24.0
25.893
28.5
25.984
8.5
Source
: From Zheng et al. [
63
]
Table 4.6
Nanoindentation hardness and Young's modulus of the original, eroded, and
remineralized enamel surfaces
Tooth number
Surface
1
2
3
Overall
Hardness/GPa
Original
5.93 ± 0.30
5.72 ± 0.16
5.60 ± 0.20
5.75 ± 0.16
Eroded
1.80 ± 0.30
1.61 ± 0.23
1.40 ± 0.16
1.60 ± 0.20
Remineralized
3.48 ± 0.33
2.66 ± 0.23
2.20 ± 0.19
2.78 ± 0.65
F
222.47
524.31
775.45
84.16
P
<0.001
Young's
modulus/GPa
Original
99.74 ± 10.03
99.71 ± 3.33
94.47 ± 5.03
97.97 ± 3.03
Eroded
71.09 ± 4.28
62.96 ± 6.02
60.62 ± 8.88
64.89 ± 5.50
Remineralized
81.39 ± 8.27
75.16 ± 7.60
70.95 ± 7.31
75.83 ± 5.25
F
16.86
50.00
25.72
38.16
P
<0.001
Source
: From Zheng et al. [
63
]
a specifi c preferred orientation because its XRD pattern had a sharp and well-
defi ned peak corresponding to the (002) crystal plane of HA. However, no well-
defi ned peak at 2
= 25.9° was observed for the remineralized surface. Hence, it
could be inferred that the crystals on the remineralized surface had no obvious pre-
ferred orientation. Moreover, the intensity of the peak at 2
θ
= 31.7° was decreased
for the remineralized surface. That is to say, the crystallinity on the remineralized
surface was lower than that on the original surface.
The hardness and Young's modulus of the indentations on the original, eroded,
and remineralized surfaces are listed in Table
4.6
. The hardness and Young's modu-
lus of the enamel surface decreased by 72 % and 34 %, respectively, after 10 min of
erosion in 0.001 M citric acid. After 12 h of remineralization in artifi cial saliva, the
hardness and Young's modulus increased signifi cantly, from 1.60 and 64.89 GPa to
2.78 and 75.83 GPa, respectively. However, both the hardness and Young's modulus
of the remineralized surface were still lower than those of the original surface. One-
way ANOVA revealed signifi cant differences in mechanical properties on these
surfaces of enamel (
P
< 0.001).
The relationship of the friction coeffi cient versus normal load is shown in
Fig.
4.34
. Figure
4.35
gives the typical friction curves of the friction coeffi cient
versus displacement at the normal load of 20 mN. The coeffi cient of friction
θ
