The possible qualitative and/or quantitative alterations in the proportions of cultivable groups of oral microorganisms were analysed during a clinical trial involving the consumption of fructose (F) or xylitol (X) in comparison to sucrose (S). Supragingival plaque samples and paraffin-stimulated saliva were collected from 115 subjects. The samples were dispersed by sonication, diluted stepwise, plated on blood sugar, Mac Leod agar, Mac Concey agar, Rogosa S.L. agar, and Sabouraud agar plates and incubated anerobically and/or aerobically. The number of the total colony forming units (CFU) on blood agar plates in anaerobic incubation was about 1-3 X 10(9)/ml saliva and 1-4 X 10(8)/mg plaque and in aerobic respectively 5-18 X 10(8)/ml saliva and 10(8)/mg plaque. The total CFU on Mac Leod agar was of a similar order of magnitude. The variation between subjects and consecutive determinations was of a similar order of magnitude. The variation between subjects and consecutive determinations was relatively large. The arithmetic mean of the total CFU on Mac Concey agar was about 1-5 X 10(5)/ml saliva, on Rogosa S.L. agar 6-130 X 10(3)/ml saliva and on Sabouraud about 1-2 X 10(3)ml saliva, all in aerobic incubations. Replacement of dietary sucrose with xylitol did not affect the proportion of major microbial categories in saliva or dental plaque. The percentage of typical streptococcal colonies on blood agar was of a similar order of magnitude (about 60-70%) during the diets. The arithmetic and geometric means of the total CFU values on Rogosa and Sabouraud agar plates were significantly lower in the X-group than in the S- or F-groups after a diet period of some months. It was thought that the reason for the reduction of acidogenic and aciduric oral flora in the X-group was partly due to the fact that xylitol is generally not metabolized by these microorganisms.

Agar↗

PubMed1976

Turku sugar studies X. Occurrence of polysaccharide-forming streptococci and ability of the mixed plaque microbiota to ferment various carbohydrates.

Dental plaque samples collected from the subjects during the last 20 months of the 2 year trial were subjected to quantitative and qualitative analysis of the occurrence of S. mutans, S. sanguis, S. salivarius and the total growth on phenol red agar. Lyophilized plaque samples were homogenized and incubated on a sucrose containing medium under anaerobic conditions. In addition, the pH-values were measured after incubation of the mixed plaque flora in media containing 1% respectively xylitol(X), sorbitol, sucrose (S), fructose (F) or no carbohydrates. The results show a significantly lower incidence of S. mutans in the X-group relative to the S- and F-groups. The corresponding difference could not be observed between the S- and F-groups. The logarithmic means and standard deviations of the colony counts of S. sanguis, S. salivarius and total bacteria yielded no significant differences between the 3 sugar groups during the test period. Repeated pH-measurements, carried out at the 4, 12, 18 and 24 month phases, showed that, except in the presence of X, the mean values all fell below the pH-limit of 5.5. In the course of the study, no evidence was obtained of adaption of mutation enabling acidogenic decomposition of X. These findings emphasize the importance of low acidogenic potential in dental plaque, generally paralleled by a low incidence of dental caries.

Bacteriological Techniques↗

PubMed1976

Turku sugar studies XX. Microbiological findings and plaque index values in relation to 1-year use of xylitol chewing gum.

The aim was to study possible alterations in the microbial flora of plaque and saliva in relation to partial substitution of dietary sucrose with xylitol. The development of plaque index values was observed simultaneously. These observations were carried out during a 1-year clinical trial, the effects of sucrose (S) and xylitol (X) chewing gum on the incidence of dental caries being observed in 100 young adults. Paraffin-stimulated saliva samples were diluted stepwise and cultivated on Rogosa S.L. agar and Sabouraud agar aerobically. Lyophilized dental plaque samples were cultivated on phenol red agar under anaerobic and aerobic conditions. The pH-values were measured after incubating the mixed plaque flora for 1 and 7 days in the presence of various sugars. Both the arithmetic and geometric means of the total CFU values on Rogosa S.L. agar decreased in the S-group at the 6-month phase but returned to the starting level after one year, whereas in the X-group they decreased or remained on the starting level. At the 6-month phase the difference between the groups was significant (U-test, p = 0.0013) and almost significant (U-test, p = 0.0569) at the end of the study. No significant differences or changes could be seen between or within the groups on Sabouraud agar. The geometric mean values of S. sanguis and S. mutans as well as the total CFU values on phenol red agar decreased considerably in both the S- and X-groups, but no significant differences could be detected in any of the streptococcal counts between the groups. The pH of the carbohydrate-containing culture media infected with mixed dental plaque significantly decreased, with the exception of the xylitol containing ones in which the pH values were not lowered even after 7 days' incubation. A significant decrease in plaque formation in relation of chewing per se was demonstrable. The difference in the plaque index values equalling or exceeding 2 was significant between the S- and X-groups. No bacterial adaptation to utilize xylitol occurred during the trial.

Chewing Gum↗

PubMed1975