Biomedical Engineering Reference
In-Depth Information
studied. Based on the given test conditions, the main conclusions can be summa-
rized as follows:
1. Artifi cial saliva can play both a cooling and lubricant effect during the wear pro-
cess. The risk of burning the tooth texture may be greatly reduced in the artifi cial
saliva condition in comparison with the dry condition.
2. Due to the lubrication and the stress decentralization of food slurry on the con-
tact surface, human teeth had a better wear resistance in a food slurry medium
than in an artifi cial saliva medium. Therefore, both a low friction coeffi cient and
a small wear depth were observed in a food slurry medium. In addition, increas-
ing the load could result in more wear of teeth, and the effect of the normal load
was more signifi cant in an artifi cial saliva medium than in a food slurry medium.
3. A competitive mechanism existed between the mechanical action and the chemi-
cal action when enamel wear occurred in the citric acid solution. Under a low
normal loading level, the surface softening of enamel caused by erosion dissolu-
tion played a signifi cant role in its wear behavior, and the wear mechanism of
enamel was dominant by adhesion delamination. Hence, enamel wear in the cit-
ric acid solution was signifi cantly higher than in the artifi cial saliva. With the
load increasing, brittle fracture by loading force was intensifi ed, and enamel
wear was gradually characterized by mechanical removal because of its inherent
brittleness. The wear morphology and loss of enamel in the citric acid solution
were similar to those in the artifi cial saliva.
4. At the early stage of erosion, the surface lesion of enamel was characterized
mainly by partial demineralization and decreased microhardness without obvi-
ous substance loss. As the erosion time increased, a honeycomb-like structure
appeared on the enamel surface as a result of severe dissolution of the enamel
rods. Then substantial erosive substance loss happened. The loss increased
almost linearly with the erosion time. Furthermore, the erosion properties of
enamel were closely associated with its location. Erosive substance loss increased
from the outer to the interior enamel. Additionally, enamel erosion had a signifi -
cant infl uence on its friction and wear behaviors. Both the friction coeffi cient and
wear loss of eroded enamel showed a strong dependence on erosion time.
Compared with the outer enamel, the infl uence of erosion on subsequent friction
and wear behavior appeared more signifi cant in the interior enamel.
5. Remineralization in artifi cial saliva could improve the antiwear properties of
acid-eroded enamel. A layer of mineral deposits was formed on the acid-eroded
enamel surface after in vitro remineralization. Compared with the original
enamel surface, this layer had a similar chemical composition but a signifi cantly
different crystal orientation. The nanomechanical and microtribological proper-
ties of the acid-eroded enamel surface were signifi cantly enhanced by remineral-
ization. However, the loss of hardness and Young's modulus of enamel surface
by acid erosion could not be totally recovered after in vitro remineralization. The
wear volume of acid-eroded enamel decreased obviously after remineralization,
but it was still much higher than that of the original enamel.
