Biomedical Engineering Reference
In-Depth Information
streptococci
[2,3]
. Moreover, Staphylococcus aureus (S. aureus), giving rise to pharyngeal and respi-
ratory infections, has been isolated from dentures and the oral cavity in elderly patients with
decreased immunological activity
[4,5]
. Therefore, the maintenance of tissue conditioner and the
prevention of the accumulation of microorganisms on such materials are of great importance. Tissue
conditioners could be kept clean by mechanical and chemical methods. However, it is also known
that these methods can cause considerable damage to tissue conditioner
[6,7]
and to some geriatric
or hospitalized patients, even denture cleansing might be compromised owing to cognitive
impairment, reduced motor dexterity, and memory loss. Though systemic or local antibiotic agents
have been prescribed for eliminating the microbial population, considering the microbial resistance
and the increase in health-care cost, the research on latent antimicrobial material may be needed
[8,9]
. Several in vitro and in vivo studies have shown the beneficial effects of antimicrobial agents
combined in tissue conditioners
[10
12]
. However, bacteria may induce stomatitis
[13,14]
and no
potentially effective and persistent antimicrobial agent that can be incorporated in tissue conditioners
has yet been developed. Silver (Ag) has been well known for its antimicrobial properties and has a
long history of application in medicine with well-tolerated tissue response and low toxicity profile
[15]
. Ag is more toxic than many other metals against a broad spectrum of sessile bacteria and fungi
which colonize on plastic surfaces
[16,17]
. Such antibacterial characteristics of Ag has drawn atten-
tion recently due to the emergence of antibiotic resistant bacteria as a result of overuse of antibiotics
and far lower propensity to induce microbial resistance than antibiotics. Ag-contained materials have
been already used in various medical fields, such as in vascular graft, central venous catheter, and
wound dressing
[18,19]
. Particularly, silver nanoparticles (Ag
), the nanosized (nm) inorganic parti-
cle form of Ag, with its rapid and broad-spectrum efficacy and sustained release of silver cation
(Ag
1
)
[18,19]
appear to be more effective means of prophylaxis than microsized (
m) Ag powder
ยต
which shows lower antimicrobial activity owing to its limited surface
[19,20]
.
Evaluating the biocompatibility of an antimicrobial material is an essential step toward the clini-
cal application of the material in addition to testing its physical properties. Through minute elution
of Ag
1
, the cations may accumulate in oral epithelial cells or when large areas of oral mucosa are
exposed to Ag
compounds over an extended period, it can possibly cause argyria or disruption of
normal microflora
[21,22]
.
The following sections of this chapter discuss the in vitro (i) synthesis of Ag
dental acrylic gel
polymer and (ii) the antimicrobial effect and cytocompatibility of the modified acrylic tissue condi-
tioner containing Ag
.
14.2
Preparation and identification of silver nanoparticles
Ag
was prepared using the following procedure. Aqueous silver sol was prepared with 10.0 mM of
analytical grade AgNO
3
in distilled water and 2.0% polyvinyl pyrrolidon was used as stabilizer. All
solutions were deaerated by bubbling with argon gas for 1 h and then were irradiated in the field of
20KGy
60
Co Gamma-ray sources. The transmission electron microscope (TEM) image of prepared
Ag
nanoparticles shows that the average size of the Ag
is about 50
80 nm (
Figure 14.3
). The
UV-vis spectrum of the Ag
is shown in
Figure 14.4
, the peak at 409.7 nm is the surface plasmon
band of the Ag
synthesized by the gamma irradiation reduction.
