Biomedical Engineering Reference
In-Depth Information
5.4
Comparison of the Wear Behavior of Enamel
Rod and Interrod Enamel
It is well known that the protein-rich interrod enamel plays an important role in the
wear behavior of tooth enamel. To compare the tribological behavior of enamel rods
and interrod enamel, we performed the scratches perpendicularly to the axis of the
enamel rod on the longitudinal section of the tooth sample. The variations in friction
forces with the sliding distance are plotted in Fig.
5.19
and the AFM images of the
scratches are shown Fig.
5.20
.
When the scratching load was 5 mN, the friction force almost kept constant dur-
ing the scratching process, as shown in Fig.
5.19
. The corresponding AFM image
(Fig.
5.20a
) reveals that no obvious difference was found from the scratch on the
enamel rods and that on the interrod enamel. When the load reached 20 mN, the
friction force began to fluctuate while the tip moved across the enamel rods and
interrod enamel. At the same time, the scratching damage revealed large differences
between enamel rods and the interrod enamel (Fig.
5.20b
). The scratch-induced
damage on a typical location of interrod enamel is magnified in Fig.
5.20d
, and the
cross-sectional profile is plotted in Fig.
5.20e
. Compared to the adjacent enamel
rods, a hole that is ≈1.7 μm in diameter and ≈30 nm in depth was formed at the
location of the interrod enamel. The diameter of the hole can be called the “func-
tional width” of the interrod enamel, which is a little wider than the width of the
interrod enamel (≈1 μm) [
23
]. Clearly, the interrod enamel showed a much weaker
wear resistance than the enamel rods. The reason may be mainly attributed to the
relatively lower hardness in the interrod enamel [
5
]. However, when the load was
further increased to 50 mN, no obvious variation was detected from the scratch-
induced damage on the enamel rods and interrod enamel (Fig.
5.20c
), which may be
due to the enamel collapsing from the applied pressure.
9
6
50 mN
3
20 mN
Fig. 5.19
Friction force
versus sliding distance curves
obtained from the scratching
tests along the direction
vertical to the enamel rod's
axis
0
5 mN
0
10
20
30
Distance (
µ
m)
