Objectives:
This study was designed to identify potential probiotic candidate strains for
prevention of dental caries. Methods: Suspensions of Lactobacillus
gasseri YIT 12321, Lactobacillus fermentus YIT 12320, Lactobacillus
crispatus YIT 12319 and Lactobacillus crispatus LBS 17-11 were prepared in PBS from 16 hrs fresh
cultures in Lactobacilli MRS (MRS) broth. Similarly, suspensions of Streptococcus
mitis YIT 12322 and Streptococcus sobrinus were prepared in PBS from 16 hrs fresh
cultures in Tryptic Soy (TS) broth. Square-shaped bovine
enamel coupons were divided into three groups and placed on
the Teflon holder around a flat-bulb pH
electrode inside three chambers of an oral biofilm reactor. Artificial biofilms were grown on the
coupons using above suspensions, TS and MRS mixed broth with sucrose and PBS for
16 hrs at 37°C in all chambers. S.
sobrinus suspension was used in chamber-I (control group), a mixed
suspension of S. sobrinus & one of the above test bacteria was used in
chamber-II and the same test bacteria was used in chamber-III in
an individual experiment and all test bacteria were examined similarly in separate
experiments. In all experiments, pH on the electrode was
recorded continuously. Turbidity and water-insoluble
glucan of the biofilms were measured separately.
Surface microhardness of the enamel surfaces was measured before and after
biofilm formation. Results: The fall of pH beneath the biofilm
formed by S. sobrinus and L. gasseri YIT 12321 or L. crispatus YIT 12319 was unusually slow keeping the pH level above 5.0 for 12 hrs. The
amounts of the mixed biofilms were significantly less than the control group. The
reduction of enamel microhardness induced by the mixed
biofilms appeared to be less than the control group. Conclusions: L. crispatus YIT
12319 and L. gasseri YIT 12321 appear to have the probiotic potential in preventing dental caries.