Biomedical Engineering Reference
In-Depth Information
(A)
(B)
O
O
Si
R
O
R
Si
SiO
2
SiO
2
OH
OH
+
Where R groups are -NH
2
, -PEG, -N(CH
3
)
4
, -SH, -Halogen (Cl, Br, I)...
FIGURE 4.5
The silica surface (A) has silanol groups. To modify the surface, the modified ligand, organosilane, will have a
silane group necessary for chemical bonding and a functional group (R), which can alter the surface charge
or be used for an additional coupling reaction (B).
altering their biological effects. Surface modification might also increase adherence to external sur-
faces as well as within composite resins (
Figure 4.7
).
Once again, the rather unique mechanical intent of dental applications suggests that the funda-
mentals which are often applied to biomedical purposes may be different. For example, a common
modification used in dentistry is addition of
-MPS) to
silica-based nanomaterials used to improve adhesion of the nanoparticles within the resin matrix, as
well as to reduce agglomeration, discussed in more detail below. This adhesive property may be
beneficial in dentistry; however, these types of particles would not be very useful for systemic
applications required in the development of a therapeutic for cancer, for example. For such sys-
temic applications, particles are often surface modified with polyethylene glycol (PEG or
PEGylation) which decreases phagocyte system uptake and increases in vivo half-life
[46,47]
.To
date, attempts to use biological active modifications of silica-based nanomaterials in dentistry have
not been reported.
γ
-methacryloxypropyltrimethoxysilane (
γ
4.5
Dental applications of silica-based nanomaterials
The structured matrix and physical properties of dentition and the skeleton are very well suited for
the application of silica-based nanomaterials. Studies investigating the use of controlling the physi-
cochemical properties of silica nanomaterials for dental applications have only begun to be realized
(summarized in
Table 4.2
).
4.5.1
Composite resins
Composite resins generally consist of a resin polymer matrix, inorganic filler, coupling reagent, col-
oring agent, and initiator
[59]
. Three key properties of composite resins used in dental applications
are mechanical, physical, and esthetic qualities all of which can be enhanced by silica. Although
silica has long been used as the reinforcing filler, the potential novel properties introduced by the
