Authors: Rolla G, Scheie AA, Ciardi JE.

Summary: Results are presented which support the concept that the bacterial enzyme glucosyltransferase (GTF) plays a crucial role in sucrose induced plaque formation. GTF was shown to adhere strongly to anionic, hydrophobic and polysaccharide solid materials, and to be able to produce glucans in the adsorbed state.

It appears conceivable that GTF adsorb to teeth and produce glucans. Glucan chains on the surface of the bacteria and glucans on the tooth surfaces interact (pack) and form a strong binding mechanism. The rigid alpha 1,3 linked glucans produced by Streptococcus mutans are particularly suited for interaction of this kind. This mechanism could account for sucrose-induced binding of bacteria to enamel, pellicle covered enamel and preformed plaque. S. mutans would adhere particularly strongly to tooth surfaces in the presence of sucrose, according to this model.

Study link: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=3159073&query_hl=28

Authors: Hartemink R, Quataert MC, van Laere KM, Nout MJ, Rombouts FM.

Institution: Department of Food Science, Wageningen Agricultural University, The Netherlands.

Summary: Fructo-oligosaccharides (FOS) are claimed to have a positive effect on the intestinal flora. They are being used in functional foods in Japan and Europe. This group have tested the degradation of two commercial FOS preparations by oral streptococci in order to predict the cariogenicity of these products. Both preparations could be fermented to some extent by the species of oral streptococci tested.

The enzymes necessary for the degradation of FOS were inducible. Each strain showed a specific degradation pattern. All strains, particularly Streptococcus mutans rapidly produced acid, mainly lactic acid. Streptococcus mitis also produced high concentrations of acetic acid. Plaque formation by Strep. mutans was similar to the sucrose control. It is concluded that FOS are cariogenic to a similar extent as sucrose.

Study link: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=8567492&query_hl=21

Authors: Minah GE, Loesche WJ.

Summary: Sucrose metabolism by resting-cell suspensions of pure cultures of representative members of the predominant cultivable flora isolated from cariogenic and non-cariogenic dental plaque was investigated by means of radiochemical techniques. Streptocococcus mutans utilized sucrose at a considerably faster rate than S. sanguis, S. mitis, Actinomyces viscosus, A. naeslundii, or Lactobacillus casei, forming lactic acid, intracellular polysaccharide, insoluble extracellular glucan, and lactic acid from intracellular polysaccharide catabolism at faster rates than the other bacteria.

The Actinomyces formed more volatile acids than the streptococci, mostly acetic, and S. sanguis formed more soluble extracellular polysaccharide than the other bacteria. The metabolic activity of S. mutans resembled the pattern of sucrose metabolism of cariogenic plaque, whereas the metabolic activity of the Actinomyces species, the predominant members of non-cariogenic plaque flora, resembled the sucrose metabolism of non-cariogenic plaques.

Study link: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=407163&query_hl=21

Authors: Kalfas S, Maki Y, Birkhed D, Edwardsson S.

Institution: Department of Oral Microbiology, School of Dentistry, University of Lund, Malmo, Sweden.

Summary: The acid production from sorbitol and glucose was studied under anaerobic conditions in resting cell suspensions of bacteria from the predominant sorbitol-fermenting human dental plaque flora, belonging to the genera Streptococcus, Lactobacillus and Actinomyces.

The acid production activity of the bacterial cells was followed by titration with alkali, at environmental pH 7.0, 6.0 and 5.0 after addition of carbohydrate solution. The metabolic end products formed in the suspensions were analyzed thereafter by isotachophoretic and enzymatic methods. The results showed that sorbitol was fermented at a slower rate than glucose.

Lowering the environmental pH decreased the acid production activity from the two carbohydrates. Compared with glucose, the catabolism of sorbitol was affected to greater extent by the pH conditions. The total amount of acids formed from sorbitol was considerably less than from glucose. Lactic acid, which was the major end product in glucose-challenged suspensions, was produced only in low concentrations from sorbitol by all strains tested.

The ratio strong (formic + lactic)/weak acids was moreover lower for sorbitol than for glucose. The present results further illustrate some of the mechanisms behind the low cariogenic potential of this sugar substitute.

Study link: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=2111221&query_hl=19

Authors: Birkhed D, Imfeld T, Edwardsson S.

Institution: Department of Cardiology, Faculty of Odontology, University of Goteborg, Sweden.

Summary: pH changes in human dental plaque in vivo from lactose and milk have been studied in four separate mouthrinse experiments. (1) pH was measured in plaque samples of 12 subjects before and after 6 weeks of frequent daily mouthrinsing with 10% lactose.

The pH decreases were significantly more pronounced after the adaptation period than before (p < 0.001), 4 of the 12 subjects showing about the same low plaque pH from lactose as from glucose. (2) Similar to the previous experiment, frequent daily mouthrinsing with low-fat bovine milk in 10 subjects resulted in more pronounced pH decreases in plaque after an adaptation period of 4 weeks (p < 0.001). (3) Single mouthrinses, without any prior adaptation, with bovine standard milk, human breast milk, lactose-hydrolysed bovine standard milk, 5% lactose and 5% sucrose were compared regarding the effect on plaque pH in 7 subjects.

All solutions resulted in pH falls. The most pronounced were found with sucrose, followed by the lactose-hydrolysed milk. (4) Bovine standard milk, 5% lactose and 10% sucrose were compared after a single mouthrinse in 5 subjects using interdental plaque pH wire telemetry.

Lactose and milk were fermented more slowly than sucrose. In a separate study, acid production from lactose was also measured in two oral strains each of Streptococcus mutans, Streptococcus salivarius and Streptococcus sanguis. The results from these experiments indicated that at least part of the lactose transport and catabolism in all studied streptococcus strains seems to be regulated by inducible enzymes.

Study link: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=8448773&query_hl=17