Relationship between a Fermented Milk Beverage and Factors Involved in Dental Caries Formation

Abstract

1) After administration of a fermented milk beverage, the behavior of antibiotic-labeled Lactobacillus casei subsp. casei PSR 3001, with which the beverage was produced, was examined in the mouth under various conditions, using human subjects, male and female, at ages from in their twenties to in their thirties.
In the control group, the bacteria was found to be at 10^5-7 per cc in saliva and at 10^3-5per cc in dental plaque immediately after administration. The bacterial population sharply reduced to the level of 10² per cc in saliva and was virtually eliminated in dental plaque after 24 hours.
In groups with treatment of either tooth brushing before administration or mouth rinsing after administration, no difference could be detected in the pattern of the bacterial behavior. And also, giving sugar-rich foohdstuffs at intervals during the test period did not affect the behavior of the bacteria.
Regardless of the presence or not of dental caries no difference was observed in the behavior of the bacteria following the administration.
In control group, mouth rinsing group, and tooth brushing group, the correlation coefficients for the declining numbers of the bacteria between saliva and dental plaque were calculated to be 0.65, 0.91, and 0.67, respectively, showing a signigcant relationship (P<0.01).
2) Productivity of extracellular polysaccharides and characteristics of sugar fermentation by Lactobacillus casei subsp. casei, a strain used for the production of a fermented milk beverage, was examined in comparison with those of Str. mutans BHT and Str. mutans OMZ 176-1 as control.
When grown in Rogosa's medium containing sucrose, L. casei did not produce any significant amount of either water-soluble or water-insoluble polysaccharides in the culture broth, while large amounts of both polysaccharides could be recovered from Str. mutans culture broth (1, 043mg and 417mg per liter for water-soluble and water-insoluble polysaccharides, respectively).
In ability to ferment polysaccharides, Str. mutans was shown to be able to utilize the watersoluble polysaccharide produced by itself, but not a commercially available dextran. L. casei, on the other hand, could not ferment either type of polysaccharide.
Regarding the acid production from sugars, L. casei consumed glucose effectively to produce acid, the concentration of which reached its maximum after 48 hours, whereas, when grown on sucrose, no acid production was observed until 48 hours, with active production thereafter. With Str. mutans, acid production from both glucose and sucrose proceeded rapidly, and its concentration reached the maximum level within 24 hours.
In a mixed culture of L. casei and Str. mutans, the amount of water-insoluble polysaccharide produced was less than that synthesized by a single culture of Str. mutans.