Biomedical Engineering Reference
In-Depth Information
often have different dimensions, morphologies, and orientations
from the natural ones, which result in a poor adhesion and
mechanical strength during dental restoration. Recent advances in
biomineralization also indicate that features of smaller particles of
nano-sized HA might approximate features of biological apatite more
closely than features of the larger HA particles that are conventionally
used [13]. For example, it has been demonstrated that nano-sized
HA can be self-assembled to form enamel-like structures in the
laboratory [193]. Therefore, a biomimetic technique is suggested as
follows: the localized repair of the enamel surface can be improved
by nano-sized HA (dimension of ~20 nm), analogues to the basic
building blocks of enamel rods. Furthermore, it is found that nano-
sized HA can adsorb onto the enamel surface strongly and can even
be integrated into the natural enamel structure [597].
It is surprising but nano-sized HA of ~20 nm can inhibit
significantly a mineral loss from the enamel surface [196]. Without
any treatment, the demineralization of the natural enamel surface
was remarkable in acidic solution (pH ~4.5 ± 0.1, experimental
period of 2 days) and damaged sites were observed. The mass loss
rate was about 0.12 ± 0.04 mg/mm
2
per day. In contrast, a layer of
nano-sized HA on the treated enamel surface was almost unchanged
in acidic solution. The rate of mass loss of enamel coated by nano-
sized HA approached zero (< 0.02 mg/mm
per day), which was
beyond the sensitivity of the detection methods. Since the coating
by nano-sized HA appeared to be insensitive to dissolution, the
underlying enamel surface was well protected under slightly acidic
conditions. Furthermore, the enamel surface coated by ~20 nm-
sized HA had a hardness of 4.6 ± 0.4 GPa and an elastic modulus
of 95.6 ± 8.4 GPa. These data appeared to be very similar to those
of natural enamel samples, which are 4.2 ± 0.2 and 94.1 ± 5.4 GPa,
respectively [196].
The similarity between ~20 nm-sized HA and building blocks
of dental enamel results in a good fixation of artificial biomaterials
to natural tissues. Moreover, the enamel structure appears to be
reinforced by nano-sized HA since secondary caries formation is
suppressed and hardness is retained [589, 598, 599]. This strategy
may have prospective applications in dentistry as it offers an easy
but effective method to reconstruct tooth enamel that is suffering
from mineral losses. Generally, these studies also suggest that
2
Search WWH ::
Custom Search