-Abstract-
A number of antiplaque agents have been available in dentifrices to decrease the
bacterial number of dental plaque. S. mutans and L. casei were most closely associated
with caries in humans. We have previously studied the in vitro mono-cultured microbial
model. This study was performed to advance this model to the di-cultured microbial
model into be suitable for testing the effect of dentifrices containing antiplaque agents,
and to evaluate the efficacy of the di-cultured microbial model.
S. mutans and L. casei were cultured in tryptic soy broth medium for 14 hours at 37℃,
5％ CO2. These bacteria were at the exponential phase for 12 hours. After
culturing for 12 hours, the density was 7.57Log10CFU/ml for S. mutans,
7.51Log10CFU/ml for L. casei, and the optical density at 540nm was 0.359,
0.258, respectively.
These bacteria were cultured in TS-MRS broth medium with 5％ sucrose according to
the mixed ratio of 1:1, 1:1/100, and 1/100:1 for each bacterium. The growth of S. mutans
and L. casei was not disturbed each other in the mixed culture, being the same growth
rate as mono-cultures. Therefore, we selected the same density of bacteria in the mixed
culture.
Incipient caries lesion was created by the solutin containing 0.1M lactic acid, 0.2％
carbopol, and 50％ saturated HAP for 44 hours at 37℃. Specimen was selected in the
range of 25VHN-45VHN. Salivary pellicle was formed by immerging in human whole
saliva for 24 hours. Plaque was formed on the enamel surface by the mixed culture in
TS-MRS with 5％ sucrose for 3 days. This medium contained the salivary salt or not,
and the interval of medium change was 8 hours or 12 hours. Specimen hardness did not
significantly changed and the density of bacteria adhered to enamel surface was 6.30±
0.19Log10CFU/㎟ for S. mutans, 5.04±0.55Log10CFU/㎟ for
L. casei when medium with the salivary salt was changed at 8 hours interval for 3
days.
Salivary pellicle was formed on the enamel specimens at the above condition. Treatment
regimens were a placebo, 1,100ppm F NaF/silica dentifrice, and 1,100ppm F NaF/silica
plus 0.3％ triclosan dentifrice. Artificial saliva contained gastric mucin(0.22％), NaCl(0.03
8％), CaCl2·2H2O(0.0213％),
KH2PO4(0.0738％), and KCI(0.1114％). The specimens were
treated with the arificial saliva, mixed whole saliva and dentifrice, and TS-MRS broth
with 5％ sucrose sequentially according to the microbial cyclic sequence for 15 days.
The delta VHNs of specimens treated with 1,100ppm F NaF/silica plus 0.3％ trclosan
were statistically higher than those treated with 1,100ppm F Naf/silica dentifrice or
placebo dentifrice. And S. mutans was fewer adhered to those treated with 1,100ppm F
NaF/silica dentifrice plus 0.3％ triclosan than those treated with placebo dentifrice plus
0.3％ triclosan than those treated with 1,100ppm F NaF/silica dentifrice or placebo
denfirice.
In conclusion, it is suggested that the in vitro di-cultured microbial pH cycling model
used in this study may be suitable for testing the effect of the dentifrices containing
antiplaque agents.
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