Bacillus subtilis Var. Natto Can Contribute to the Treatment of Dental Caries

Objectives: Natto is a popular, traditional Japanese fermented food. Bacillus subtilis var. natto, which belongs to the Bacillus genus, is used to produce natto. As B. subtilis is nonpathogenic to humans and produces a number of useful substances, this bacterium is used as a probiotic. Mineral trioxide aggregate (MTA) cement is a highly alkaline endodontic material and due to its high alkalinity, MTA cement exhibits antibacterial properties.
Clinical experiments have shown that indirect pulp capping with a mixture of MTA cement and B. subtilis spore powder is extremely effective in avoiding pulpectomy or tooth extraction [personal communication]. This research aimed to provide a scientific basis for the hypothesis that a combination of B subtilis and MTA cement would be clinically useful for dental caries treatment.
Methods: Bacillus subtilis var. natto Takahashi strain (Yuzo Takahashi Laboratory, Yamagata, Japan) and NEX MTA cement (GC corporation, Tokyo, Japan,) were used.
The experiments focused on whether usefulness of B. subtilis can be demonstrated in a severe environment, such as high alkaline, low oxygen, and exposure to antibacterial property possessed by MTA cement.
Results: The experiments showed the following results: (1) B. subtilis did not proliferate in liquid-culture media with a pH of ≥10. (2) B. subtilis proliferated from mixtures with MTA cement. (3) No significant differences in the proliferation of B. subtilis were noted under aerobic and microaerobic conditions. (4) B. subtilis exhibited antibacterial effects on Staphylococcus aureus and Lactobacillus casei. (5) MTA cement exhibited antibacterial effects on Staphylococcus aureus and Streptococcus mutans, but not B. subtilis. (6) The liquid culture containing B. subtilis decreased the adhesion of S. mutans.
Conclusions: These results support the hypothesis that a combination of B subtilis and MTA cement is clinically useful for dental caries treatment.