Biomedical Engineering Reference
In-Depth Information
14.3
Acrylic tissue conditioner combined with silver nanoparticles
14.3.1
Fabrication of Ag
-tissue conditioner composites
The acrylic tissue conditioner selected for this study was Soft-Liner
s
supplied as powder and
liquid. Colloidal Ag
was preliminary combined and homogenized with the conditioner liquid in a
sterile glass beaker at concentrations ranging from 0 (control), 0.1, 0.5, 1.0, and 2.0% (vol/vol%:
colloidal Ag
/conditioner liquid), respectively. The conditioner powder was immediately added and
mixed for 30 s at designated powder/liquid ratio by manufacturer's instruction. In order to fabricate
samples into uniform shape with regular surface, the mixed paste of conditioner was poured onto a
custom-made brass mold with dimensions of 20 mm diameter
3.0 mm depth. The mixed paste
was sandwiched between glass slides until it was solidified under humid condition. Before micro-
bial assay, all samples were sterilized with ethylene oxide gas for 24 h to ensure their initial
sterility.
3
14.3.2
In vitro antimicrobial effects on
S. aureus, Streptococcus mutans
,
and
C. albicans
Three standard strains of microorganisms were used: S. aureus (ATCC 6538), S. mutans (ATCC
10449), and C. albicans (ATCC 14053). These microbial species tested are currently recommended
to test the efficacy of antiseptic drugs
[23]
. S. aureus, a pathogen causing respiratory infections,
has often been isolated from dentures and the oral cavity
[4,24]
, and dentures have recently been
reported to be a carriage of this pathogen
[25]
. S. mutans has been associated closely with the
pathogenesis of dental caries, which is of limited clinical significance for denture wearers
[26]
.
However, extensive plaque formation on denture might also contribute to the decay of residual
natural teeth and can cause inflammation of gingival tissue adjacent to the denture
[26]
. C. albicans
has been regularly isolated, suggesting a pathogenic association between bacteria and fungi related
with denture-induced stomatitis.
Microbial suspensions were obtained from single colony isolated on agar plates and inoculated
in appropriate broth for overnight cultures. Bacterial strains were grown in brain
heart infusion
(BHI) broth and plated on agar plates at 37
C while C. albicans strain was grown in Schaedler
broth and plated on agar plates at 30
C. After incubating microbial cells at 37
C overnight, optical
density (OD) of the microbial suspension at 600 nm was adjusted to 1.0 using a spectrophoto-
meter. The suspension was diluted with phosphate-buffered saline (pH 7.4) to 1:100 and suspended
to final concentration of 1.0
10
7
cells/mL
[14,27]
. Each disc sample of Ag
-tissue conditioner
and control were placed on multiwell culture plate with 22.1 mm diameter. Initial microbial
suspensions (100
3
L) in 1.0 mL of Sabouraud broth were inoculated to each well and incubated
at 37
C. A small volume of microbial suspension (100
µ
L) was used and the microbes were
adjusted to the stationary phase to be suspended in broth. The oral microbe would appear to be in
a stationary phase rather than in growing phase, when the nutrition is limited in the presence of
antibodies and antimicrobial enzymes in the oral cavity
[28]
. The assays with samples immersed
in large suspension volume could not reproduce in vivo tissue conditioner which is closely in con-
tact with the gingival mucosa
[11]
. Microbes in suspension (planktonic phase) are sensitive to
lower antiseptic concentrations than microbes colonizing surfaces protected by a biofilm
[29]
.
µ
