Biomedical Engineering Reference
In-Depth Information
enamel-like structure under physiological conditions. Importantly, the mechanical characteristics of
the repaired enamel are well maintained by using this feasible enamel remodel. These successful
approaches of enamel regeneration implies a potential of material-inspired strategy of nano
assembling in biomedical application and opens the possibility that in the future dental practice
might drastically change, allowing the manufacturing of teeth in the dental practice office.
20.4.2
Nanomaterial in enamel and dentine remineralization
The prevention of tooth decay and the treatment of lesions and cavities are ongoing challenges in
dentistry. In recent years, biomimetic approaches have been used to develop nanomaterials for the
remineralization of early enamel lesions
[55]
. Nowadays, nano-HA is widely studied as a biomi-
metic material for the reconstruction of tooth enamel suffering from mineral loss and as an effec-
tive anticaries agent because of its unique potential for remineralization
[56
63]
. Our previous
studies demonstrated that nano-HA has the potential to remineralize initial enamel caries lesions
under dynamic pH cycling conditions. In addition, a concentration of 10% nano-HA may be opti-
mal for remineralization of early enamel caries in vitro
[64]
. In further research, however we found
that nano-HA helped mineral deposition predominantly in the outer layer of the lesion and only had
a limited capacity to reduce lesion depth. Nevertheless, the remineralization effect of nano-HA
increased significantly when the pH was less than 7.0
[65]
. Further, our research showed that there
was a significant synergistic effect of combined GCE and nano-HA treatment on promoting the
remineralization of initial enamel lesion
[66]
. When GCE was added with nano-HA, significant
higher volume percent mineral was present in the body of lesion, it would not completely inhibit
the deposition of nano-HA on the out layer of lesion in the remineralization process, so full remi-
neralization on the initial enamel lesion was obtained. The SEM images showed that the crystals of
surface layer in the GCE
nano-HA group were arranged regularly and densely uniform structure
was formed (
Figure 20.4E
), whereas, irregularly arranged crystals were present in the nano-HA
group (
Figure 20.4C
).
Accumulated evidence has demonstrated that the average size of the calcium phosphate crystals
play an essential role in the formation of hard tissues and has a significant influence on its intrinsic
properties, including solubility and biocompatibility
[67,68]
. An in vitro study demonstrated that
evenly sized nano-apatite particles (20-nm-sized HA and building blocks of biological apatite of
dental enamel) could simultaneously repair and prevent initial erosive lesions in enamel compared
with conventional HA crystals that are hundreds of nanometers in length
[62]
. Our in vitro study
also demonstrated that nano-HA provides better remineralization than micro-HA. Generally, these
studies suggest that analogs of nanobuilding blocks of biominerals should be highlighted in the
entire subject of biomineralization.
In summary, the remineralization effect of nano-HA on caries lesions is clear, but the mecha-
nism of action is still open to debate. A number of researchers have proposed that nano-HA pro-
motes remineralization through excellent deposition onto etched enamel
[62]
or by depositing
apatite nanoparticles in the defects on demineralized enamel. Other researchers, however, have sug-
gested that nano-HA acts to deliver a calcium source to the mouth, which can increase oral calcium
levels, and has the potential to limit acid challenges by reducing enamel demineralization while
promoting enamel remineralization
[56
1
58]
. Based on these theories combined with our current
results, we propose that the mechanism of remineralization is that HA acts as a calcium phosphate
