Biomedical Engineering Reference
In-Depth Information
a
b
600
Control
Eroded
Pla
stic
Outer
400
Intermediate
200
Interior
0
2.00
1.50
1.00
0.50
0.00
200nm
0.5 mm
Distance from DEJ/mm
Surface profile
Variation of erosion depth as a
function of the distance from DEJ
Fig. 4.25
Surface profi le and erosion depth of the enamel at different depths [
56
]
8.0
Control
Eroded
6.0
4.0
2.0
0.0
Outer
Intermediate
Interior
Fig. 4.26
Nanoindentation hardness of the enamel at different depths [
56
]
within the interior enamel than within the outer enamel. In addition, a decrease in
fl uorine content and an increase in magnesium were found from the natural surface
to the DEJ [
51
], which could cause an increase in the solubility of enamel to some
extent [
62
]. As a result, the erosion resistance decreased from the outer to the interior
enamel. Hence, a more severe erosive lesion was observed in the interior enamel
than in the outer enamel (Figures
4.24
and
4.25
). Our fi nding was consistent with the
results of Anderson and Elliott [
60
]. They used acetic acid (pH = 4.00) as the demin-
eralizing solution and measured the rates of in vitro mineral loss of human tooth
enamel in the cross section (perpendicular to the occlusal surface). They found that
the rate of enamel demineralization increased from the natural surface to the DEJ.
The hardness of the enamel at different depths was examined using nanoindenta-
tion on both the control and the eroded surfaces, and the results are shown in
Fig.
4.26
. Each value of hardness was the average of 10 indentations under the same
