Biomedical Engineering Reference
In-Depth Information
Table 8-4. Nanoindentation elastic modulus and hardness of cementum.
25
Elastic
Modulus
(GPa)
Tooth
Sample
Sample Site and
Sectioning
Hardness
(GPa)
Authors
outer surface of
cementum
#
:
- cervical third
- middle third
- apical third
orthodontic-
treated
premolars
0.25
±
0.09
4.4
±
2.4
Srivicharnkul
et al
.
78
0.24
±
0.07
3.4
±
2.0
0.18
±
0.06
2.4
±
1.8
transversal section:
- ultrasectioned
- polished
0.48 - 1.09
*
0.79 - 0.89
*
14.2 - 25.9
*
18.2 - 20.8
*
mandibular
third molars
Ho
et al
.
79
outer surface of
cementum
#
Malek
et al
.
75
premolars
0.41
±
0.14
5.68
±
2.65
Longitudinal
section:
- middle third
- apical third
Poolthong
36
premolars
0.63
±
0.06
11.95
±
1.24
0.57
±
0.48
8.55
±
0.84
*
Range
#
Spherical indenter, others used a Berkovich indenter.
from an ultra-sectioned cementum, which clearly represent local
variations. Purified water was reported to be a better storage media,
compared to alcohol or desiccation, in which the mechanical properties
of cementum were noted to be stable for up to nine months.
80
Nanoindentation has also been applied to investigating the impact of
orthodontic treatments on tooth root. Ideally an orthodontic force should
be able to generate tooth movement without any pathological symptoms.
It is believed that excessively large applied forces may initiate resorption
in cementum. However, nano-indentations on the cementum of premolar
teeth, which had been subjected to 25 g and 250 g orthodontic loads for
four weeks showed no significant difference in their hardness and elastic
modulus.
78
The latter authors consider that this is possibly due to short
treatment period and large inter-individual variations between teeth. The
reported values are however, lower than those previously reported by
necessary to more critically evaluate spatial variations and the role of
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