Biomedical Engineering Reference
In-Depth Information
After an incubation period of 24 h and extended 72 h, suspension (100
L) was withdrawn, viable
cells colony forming unit (CFU) in the suspension was determined by using the spread plate
method at a level of detection within 500 CFU per plate through serial dilution. As no standard of
the antimicrobial effect on dental material has been established so far, the concept of minimum
bactericidal concentration of antibiotics was adopted as the antimicrobial concentration at more
than 99.9% elimination of the microbes [30,31] .
The antimicrobial effects of Ag -tissue conditioner against S. aureus, S. mutans, and C. albicans
were demonstrated as the mean viable cells after 24 and 72 h of incubation ( Table 14.1 ). When
compared to initial CFU at 0 h, control group (0% Ag ) did not exhibit any microbial inhibitory
effect against all of the strains, though the tissue conditioner itself possesses antimicrobial effects
due to ingredients such as plasticizers and ethanol [32] . Some studies have shown that the antimi-
crobial effect of these ingredients was at variance and has little antimicrobial effect [1,33] . For two
bacterial strains, S. aureus and S. mutans,Ag incorporated samples showed the minimal bacteri-
cidal effects at the dose above 0.1% and no viable cells were detected from the conditions of 1.0%
above. For fungal strain C. albicans, the minimal fungicidal concentration was shown at the dose
of above 0.5% and no CFU was detected in 2.0%. It is reported that Ag and Ag-based compounds
are highly toxic to prokaryotic cells showing strong biocidal effects on bacterial species [17] , while
Ag showed less effect on eukaryotic cells such as mold and yeasts [34] . The mechanism of antimi-
crobial effect of silver supported compound has not been fully explained yet. It was suggested that
as a result of catalytic action of Ag, oxygen is converted into active oxygen (including hydroxyl
ยต
Table 14.1 Antimicrobial Effect of Ag -Tissue Conditioner Samples (02.0%) Against S. aureus,
S. mutans, and C. albicans at 24 and 72 h of Incubation Periods
Ag Dose (Vol%)
Incubation
Period (h)
Strain a
0 (Control)
0.1
0.5
1.0
2.0
8
3
24
5.4 3 10
7.1 3 10
48 6 (66)
0
0
7
)
2
S. aureus
6 (6 3 10
6 (5 3 10
)
12 6 (4)
0
0
7
7
2
(10
)
72
8.7 3 10
9.7 3 10
6
)
2
6 (2 3 10
6 (5 3 10
)
1.2 3 10 7
3.6 3 10 3
24
30 6 (75)
0
0
6 (3 3 10 6 )
6 (6 3 10 2 )
S. mutans
7 6 (11)
0
0
(10 7 )
3.5 3 10 6
5.4 3 10 2
72
6 (4 3 10 5 )
6 (4 3 10 2 )
4.3 3 10 7
2.6 3 10 5
2.2 3 10 2
24
10 6 (25)
0
6
)
4
)
2
C. albicans
6 (9 3 10
6 (9 3 10
6 (3 3 10
)
20 6 (34)
0
7
7
4
2
(10
)
72
5.2 3 10
5.5 3 10
1.2 3 10
6
)
3
)
6 (9 3 10
6 (9 3 10
6 (75)
Results are expressed in mean CFU with standard deviation (sd). Data in bold represent values statistically different from
control (
P , 0.01).
a Starting inoculums: 10 7 CFU.
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