The effect of sorbitol on the microbiology of the dental plaque in monkeys (Macaca irus)

Health potential of polyols as sugar replacers, with emphasis on low glycaemic properties

Abstract Polyols are hydrogenated carbohydrates used as sugar replacers. Interest now arises because of their multiple potential health benefits. They are non-cariogenic (sugar-free tooth-friendly), low-glycaemic (potentially helpful in diabetes and cardiovascular disease), low-energy and low-insulinaemic (potentially helpful in obesity), low-digestible (potentially helpful in the colon), osmotic (colon-hydrating, laxative and purifying) carbohydrates. Such potential health benefits are reviewed. A major focus here is the glycaemic index (GI) of polyols as regards the health implications of low-GI foods. The literature on glycaemia and insulinaemia after polyol ingestion was analysed and expressed in the GI and insulinaemic index (II) modes, which yielded the values: erythritol 0, 2; xylitol 13, 11; sorbitol 9, 11; mannitol 0, 0; maltitol 35, 27; isomalt 9, 6; lactitol 6, 4; polyglycitol 39, 23. These values are all much lower than sucrose 65, 43 or glucose 100, 100. GI values on replacing sucrose were independent of both intake (up to 50 g) and the state of carbohydrate metabolism (normal, type 1 with artificial pancreas and type 2 diabetes mellitus). The assignment of foods and polyols to GI bands is considered, these being: high (> 70), intermediate (> 55–70), low (> 40–55), and very low (< 40) including non-glycaemic; the last aims to target particularly low-GI-carbohydrate-based foods. Polyols ranged from low to very low GI. An examination was made of the dietary factors affecting the GI of polyols and foods. Polyol and other food GI values could be used to estimate the GI of food mixtures containing polyols without underestimation. Among foods and polyols a departure of II from GI was observed due to fat elevating II and reducing GI. Fat exerted an additional negative influence on GI, presumed due to reduced rates of gastric emptying. Among the foods examined, the interaction was prominent with snack foods; this potentially damaging insulinaemia could be reduced using polyols. Improved glycated haemoglobin as a marker of glycaemic control was found in a 12-week study of type 2 diabetes mellitus patients consuming polyol, adding to other studies showing improved glucose control on ingestion of low-GI carbohydrate. In general some improvement in long-term glycaemic control was discernible on reducing the glycaemic load via GI by as little as 15–20 g daily. Similar amounts of polyols are normally acceptable. Although polyols are not essential nutrients, they contribute to clinically recognised maintenance of a healthy colonic environment and function. A role for polyols and polyol foods to hydrate the colonic contents and aid laxation is now recognised by physicians. Polyols favour saccharolytic anaerobes and aciduric organisms in the colon, purifying the colon of endotoxic, putrefying and pathological organisms, which has clinical relevance. Polyols also contribute towards short-chain organic acid formation for a healthy colonic epithelium. Polyol tooth-friendliness and reduced energy values are affirmed and add to the potential benefits. In regard to gastrointestinal tolerance, food scientists and nutritionists, physicians, and dentists have in their independent professional capacities each now described sensible approaches to the use and consumption of polyols.

Food components and caries

For many decades, sugars have been the dietary constituents receiving the most attention in relation to their effects on dental caries. Frequently, however, there is little relationship between the amount of sugar in a food and its ability to induce caries. Therefore, it is clear that constituents in the diet can influence the ability of plaque to lower the pH of sugar solutions. For instance, replacing sugar in foods with xylitol, sorbitol, saccharin, or aspartame may lead to a reduction in the incidence of dental caries. All these sugar substitutes are non-cariogenic, and some may possess cariostatic properties. The presence of arginine-rich proteins in the diet may provide a ready source of this amino acid, which is the substrate for the arginine deiminase pathway which can result in a rapid elevation of plaque pH values. Proline can act as an acceptor for protons from lactate in the Stickland reaction. This is a major but much-neglected metabolic pathway in dental plaque. The presence of fat in experimental diets has been shown to affect their cariogenicity. The effects have been ascribed to enhanced clearance of sugars from the mouth. It is also conceivable that several fatty acids express a potent antibacterial effect. The presence of calcium and phosphorus has been shown to influence the cariogenicity of foods; the effect, however, is restricted to the food containing the minerals. Evidence suggests that pyridoxine (vitamin B6) may exert a cariostatic effect by enhancing decarboxylation activity in dental plaque. It is clear that sugar alone is not the sole determinant of whether food is cariogenic. Furthermore, myriad substances may hinder or enhance the caries-promoting properties of sugars in the diet.

Distribution and isolation frequency of eight streptococcal species in saliva from predentate and dentate children and adults

The isolation frequency and distribution of eight recently defined streptococcal species have been investigated in the saliva of adults and that of both predentate and dentate children. The effects of frequency of sugar intake and tooth presence on the distribution of streptococcal species were also analyzed. Saliva samples were collected from 121 subjects divided into three study groups: (a) 56 predentate children (predentate group), (b) 37 dentate children (dentate group), and (c) 28 adults (adult group). Up to 17 biochemical and enzymatic tests were used to categorize streptococcal isolates into S. mitis, S. oralis, S. salivarius, S. anginosus, S. sanguis, S. vestibularis, S. mutans, and S. gordonii. The mean total and streptococcal salivary colony-forming units (CFU) were lowest in the predentate group and highest in the adult group. Streptococci were found in all the study subjects, and there was no obvious relationship between the total or streptococcal CFU and the number of teeth or the frequency of sugar intake. There was a wide variation in the isolation frequency of streptococcal species in the three study groups. S. mitis, S. oralis, and S. salivarius were the most frequent species isolated, and together they comprised 83% of the total streptococcal isolates. In contrast to studies using older classifications, S. sanguis was a minor species in the saliva though found more often in adults than in children (p < 0.04). S. anginosus was a minor species found in about 10% of adults and children. S. gordonii was detected rarely and only in dentate subjects. S. mutans was detected only in dentate subjects, significantly greater in adults (57.1%) than in children (5.4%, p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Can the oral flora adapt to sorbitol?

The number of non-sugar sweeteners that are approved for use in foods and drinks is increasing and manufacturers are using these as alternatives to cariogenic sugar. These non-sugar sweeteners are generally classed as non-cariogenic. The most frequently used non-sugar sweetener is sorbitol, and concern has been expressed that the oral flora may adapt to sorbitol so that it looses its 'safe for teeth' property. The purpose of this review is to describe the mechanisms whereby oral microorganisms, and mutans streptococci in particular, might metabolize sorbitol and to summarize published research into changes in plaque acid production and changes in plaque flora after exposure to sorbitol. Finally, the possibility that some groups of people may be especially 'at-risk' from adaptation of oral microorganisms to sorbitol is considered. It is concluded that frequent or long-term use of sorbitol is unlikely to present any increased risk of dental caries in normal people, but that frequent use of sorbitol may present a small cariogenic risk in people with low salivary flow.

Influence of sweetening agents in solution on dental caries in desalivated rats

Sucralose (trichlorogalactosucrose), sorbitol and aspartame in drinking water induced little or no caries in desalivated rats infected with Streptococcus sobrinus and Actinomyces viscosus and receiving their essential nutrition by gastric gavage. In contrast, sucrose and fructose induced extensive decay. Only sucrose could sustain implantation of Strep. sobrinus in these animals. The populations of A. viscosus were sparse (0.3-0.5%) in the animals given fructose and sucrose. Large populations of A. viscosus occurred in the controls and in those given sucralose, sorbitol and aspartame. In a second experiment, where animals were also desalivated and receive diet 2000 ad libitum, sucrose in solution promoted caries whereas sucralose, aspartame and saccharin were without effect. Addition of 10 parts/10(6) F overcame the caries-promoting effect of sucrose in solution. There was no interaction between fluoride and other sweetening agents that affected the incidence of caries.

Effect of sorbitol- and xylitol-containing chewing gum on salivary microflora, saliva, and oral sugar clearance

The effect of frequent use of a sorbitol-containing nicotine chewing gum on saliva secretion rate and buffer capacity and some oral bacteria was studied in 27 patients at a smoking cessation clinic. The effect was compared with that obtained after frequent use of a chewing gum containing xylitol in a second study in 14 subjects. The results showed that sorbitol-containing nicotine chewing gum had no significant effect on salivary numbers of oral streptococci and lactobacilli during a 3-month period of active chewing five times a day. Chewing on xylitol-containing gum caused a significant decrease in salivary S. mutans after 2 months but not after 3 months. No change in secretion rate or buffer capacity was observed in the two studies. Oral sugar clearance time was reduced after 3 months with a statistically significant difference to baseline values in subjects consuming the sorbitol-containing nicotine chewing gum.

Solid state adsorption of antibiotics onto sorbitol

The ability of two types of sorbitol, instant and crystalline, to hold antibiotics permanently after mixing has been assessed by an air sieving technique. Sorbitol instant was found to have a greater adsorption capacity and binding strength than crystalline sorbitol. The six antibiotics studied were found to fall roughly into two groups of different adsorption capacities: (1) pivampicillin, cephalexin monohydrate and erythromycin ethylsuccinate, and (2) ampicillin trihydrate, amoxycillin trihydrate and cloxacillin sodium. The former have slightly higher levels of adsorption than the latter. A negative linear relationship was found between the amount of antibiotic adsorbed onto dry sorbitol and that originally added to sorbitol. When adsorption is expressed as the weight of drug adsorbed per unit weight of sorbitol, an 'apparent' Langmuir isotherm results. This suggests that there are a number of adsorption sites available for holding drug particles, these sites being different for the different antibiotics.

In vivo measurements of sulcal plaque pH after topical applications of sorbitol and sucrose in rats fed sorbitol or sucrose

To test whether adaptation to sorbitol could be observed in rat plaque, we made pH measurements of rat sulcal plaque in vivo, following topical application of 10% sorbitol solution. Rat pups were inoculated orally with S. mutans 6715 and fed diet MIT 305 (5% sucrose) for 16 days. Baseline sulcal plaque pH response of these rats to topical application of 10% sorbitol solution was measured. One group of 16 rats was then fed 20% sucrose in the diet, and a second group 20% sorbitol. After 13 days' feeding of the experimental diets (four days were used for accommodation to dose, and nine days at the 20% level for sorbitol), there was a significantly greater (p less than 0.01) drop in pH following topical application of 10% sorbitol in this group than in the sucrose-fed group. There was no difference in the pH response of the two groups to topical application of a 10% sucrose solution when tested six days later. The sulcal enamel caries score was significantly higher (p less than 0.001) in the sucrose group, but buccal enamel scores were similar in both groups. Adaptation in rat plaque took place, and could be measured in vivo as an increased drop in sulcal plaque pH following topical application of sorbitol. It is not clear whether this adaptation was primarily due to selection of sorbitol-fermenting micro-organisms, or, more likely, by induction of sorbitol-specific enzymes. Relative to the sucrose-containing diet, the sorbitol diet was hypocariogenic, even under experimental conditions.

Agar media that indicate acid production from sorbitol by oral microorganisms

Two varieties of agar medium (Trypticase [BBL Microbiology Systems]-serum-sorbitol-bromcresol purple agar [TSSB] and Trypticase-blood-sorbitol-CaCO3 agar [TBSCa]) indicating microbial acid production from sorbitol were tested. The media were devised for use in studies on the prevalence of sorbitol-fermenting human oral microorganisms incubated in an anaerobic or microaerophilic atmosphere containing 5 to 6% CO2. TSSB contains bromcresol purple as the pH indicator and NaHCO3 as the main buffering salt. TBSCa contains CaCO3 as both the buffering salt and the indicator of acid production. The growth yield of pure cultures of oral microorganisms on TBSCa was shown to equal that on blood agar incubated under similar conditions. TSSB inhibited the growth of several bacteria to various extents. The recovery of sorbitol-fermenting microorganisms from oral specimens was the greatest when the specimens were assayed with TBSCa. The poorer results obtained with TSSB were mainly due to the decoloration of the pH indicator in this medium and the presence of greater numbers of sorbitol false-positive colonies.

The repressible metabolism of sorbitol (D-glucitol) by intact cells of the oral plaque-forming bacterium Streptococcus mutans

Sorbitol metabolism of Streptococcus mutans was studied. Cocci adapted to growth in sorbitol, glucose or both were challenged to grow on and to ferment those carbohydrates in pH-controlled defined media with intact cells capable of metabolic inductions and regulations. Glucose degradation when in high concentration did not depend upon induction of glucose-specific phosphoenolpyruvate-dependent phosphotransferase activity, as it did at low glucose concentrations. Sorbitol utilization was signalled by the induction of sorbitol-specific phosphoenolpyruvate-dependent phosphotransferase and sorbitol-6-phosphate dehydrogenase activities which persisted throughout the growth cycle. However, when even low levels of glucose were present, sorbitol transport and catabolic activities were rapidly repressed and they were not de-repressed until essentially all glucose had been utilized. Metabolism of sorbitol thus relies on the sorbitol phosphotransferase/sorbitol-6-phosphate dehydrogenase pathway whose activity is sensitively repressed in the presence of glucose.

Streptococcus mutans in plaque and saliva after mouthrinsing with SnF2

Mouthrinses with SnF2 in 11 subjects significantly reduced (P less than 0.01) the total colony forming units (CFU) count and the numbers of Streptococcus mutans and Streptococcus sanguis in plaque. The numbers of S. mutans and S. sanguis were significantly more reduced than was the total CFU count. After rinsing with SnF2S. sanguis was present in 97% and S. mutans in only 42% of plaque samples from tooth surfaces where they were detected after rinsing with water. SnF2 also significantly reduced (P less than 0.01) the number of S. mutans in saliva. Mouthrinses with NaF did not markedly affect the number of S. mutans either in plaque or in saliva.

The streptococcal flora of the tongue of the monkey Macaca fascicularis

The major streptococcal biotypes in the 8 monkeys investigated resembled Streptococcus sanguis and Streptococcus mitior with Streptococcus salivarius forming only 5 to 6 per cent of the total colony count and being isolated from only 4 monkeys. The predominant tongue streptococci were not isolated from the dental plaque. Similarly, Streptococcus mutans, present in large numbers in the plaque of monkeys fed sucrose-rich diets, was isolated from the tongue of only 2 animals and formed only 2.4 per cent of the total colony count. Changing from a starch-based maintenance diet to sucrose-rich diets did not significantly alter the tongue flora except that the proportion of typical Strep. sanguis was significantly reduced. The oral streptococcal flora of monkeys is similar in distribution to that found in the human mouth.

Colonization and cariogenic potential in hamsters of the bacterium Streptococcus sanguis isolated from human dental plaque

Strains of Strep. sanguis, freshly isolated from human dental plaque, were successfully implanted into albino hamsters. Transmission of the organisms from infected to uninfected animals occurred naturally. The transfer was as effective between unrelated hamsters as between dams and their offspring. Three of the strains tested did not cause caries in hamsters. Laboratory strains of Strep. sanguis did not colonize the hamsters. Two morphological variants of Strep. sanguis with different abilities to adhere to whale dentine in vitro, could infect hamsters; the more adhering phenotype was detected earlier and more frequently.

Effect of the antibacterial agents octenidine and chlorhexidine on the plaque flora in primates

The effect of the antibacterial substance octenidine on plaque formation and on oral microflora in eight monkeys fed a sucrose diet was studied. Plaque was obtained from buccal tooth surfaces of premolars and first molars in two quadrants using a swab and a dental carver and examined using culture and fluorescent antibody procedures. A significant reduction in plaque score was observed on the buccal tooth surfaces after daily topical application of 1% solutions of octenidine and chlorhexidine for 7 d; octenidine was more effective than chlorhexidine. Placebo treatment with water was without significant effect. Octenidine and chlorahexidine affected the plaque flora in a similar manner; the proportion of S sanguis increased in relation to baseline levels while the population of Actinomyces, especially the group A. viscous and A. naeslundii, was markedly reduced. S. sanguis showed an inverse relationship to members of actinomyces in response to the action of the antimicrobial agents. Both plaque sampling methods revealed similar changes in bacterial composition as a result of treatment. The data show that octenidine is an effective inhibitor of dental plaque and its antimicrobial and antiplaque properties make it worthy of further studies.

Effect of aqueous solutions of sorbitol-xylitol on plaque metabolism and on growth of Streptococcus mutans

The present study showed that the growth of Streptococcus mutans strain GS5 was inhibited by xylitol, and this indicates together with previous reports that this is a common phenomenon in this species. Sorbitol was found to increase the growth of S. mutans strains OMZ 176 and GS5 slightly compared with cultures with no external carbon source. Addition of small amounts of xylitol to the sorbitol cultures gave a growth below that of cultures with no extra carbon. Dental plaque challenged with sorbitol gave a small pH drop whereas xylitol caused a negligible decrease in pH. Sorbitol-xylitol challenges gave less acid production than sorbitol challenges alone.

Effect of chlorhexidine on the relative proportions of Streptococcus mutans and Streptococcus sanguis in hamster plaque

The effect of chlorhexidine on the proportions of Streptococcus mutans and Streptococcus sanguis in plaque was studied in hamsters fed a diet containing 28% sucrose. In animals given chlorhexidine in their drinking water for 10 d a decrease in the population of S. mutans and an increase of S. sanguis occurred in the plaque. Following the removal of chlorhexidine the population of S. mutans increased again in the presence of sucrose and the number of S. sanguis returned to initial values. When animals were given a sucrose-free diet the low proportion of S. mutans observed following the short-term chlorhexidine period persisted. These data indicate that there is an inverse relationship between the number of S. sanguis and S. mutans in plaque and that the sensitivity in vivo of S. mutans to chlorheximide can be used to suppress the population of S. mutans with a concomitant rise in the proportion of S. sanguis.

Effects of 3 months frequent consumption of hydrogenated starch hydrolysate (Lycasin), maltitol, sorbitol and xylitol on human dental plaque

Lozenges containing hydrogenated starch hydrolysate (Lycasin), maltitol, sorbitol or xylitol were consumed 4 times daily during 3 months by 4 groups of persons (in all 85 subjects). In the maltitol-, sorbitol- and xylitol-group the plque wet weights were of the same magnitude before and after the test period. In the Lycasin-group, a higher value was found after than before the 3-month period (p less than 0.01). The acid production in suspensions of dental plaque material from Lycasin, maltitol and sorbitol expressed as per cent of that from glucose was approximately the same before and after the test period. From xylitol no acid production could be demonstrated either before or after the 3-month period. There were no statistically significant differences between the plaque pH-changes induced by rinsing with 50% solutions of Lycasin, maltitol, sorbitol or xylitol before and after the test period. However, there was a tendency (p less than 0.05) towards lower pH-values induced by the maltitrol and sorbitol rinse after the 3-month period compared with before. No difference in the relative numbers of facultative anaerobic streptococci. Streptococcus mutans or facultative anaerobic lactobacilli before and after the test period was found.

Initial colonization of teeth in monkeys as related to diet

The initial phases of plaque development on nonretentive tooth surfaces were studied bacteriologically in Macaca irus monkeys fed by stomach tube and provided with various oral supplements. Except for the oral implantation of Streptococcus mutans in some of the animals, the oral flora was not changed prior to the studies. Dental plaque was allowed to develop on initially cleaned tooth surfaces for 3 to 5 h. Plaque samples were collected and cultured on a number of selective and nonselective agar media, and several hundred isolates from each sample were isolated and identified. The numerically predominant organisms in initial plaque were S. mutans, Streptococcus sanguis, and Actinomyces viscosus. Additional organisms regularly found, but usually in smaller numbers, were Streptococcus mitior and a group of fastidious gram-negative rods including Haemophilus species, Eikenella corrodens, and Actinobacillus actinomycetem-comitans. The colonization of S. mutans was dependent on sucrose and occurred at the expense of S. sanguis. In these experiments S. mutans accounted for 25 to 65% of the primary plaque formers. All other species encountered colonized the teeth irrespective of the diet. It is postulated that the early sucrose-dependent establishment of S. mutans directly on the enamel pellicle plays a key role in the development of a cariogenic plaque.

Inability of low levels of sorbitol and mannitol to support caries activity in rats

Under the environmental conditions of these experiments, neither 5 nor 10% sorbitol or mannitol in diets containing 62 or 57% corn starch, respectively, was capable of increasing the caries activity in rats above the level supported by a 67% starch diet. In contrast, 5% sucrose in the presence of 62% corn starch caused a slight increase and 10% sucrose in the presence of 57% starch caused a significant increase in caries activity beyond that observed when the diet containing 67% starch as the only carbohydrate was fed.

Role of sucrose in colonization of Streptococcus mutans in conventional Sprague-Dawley rats

The role of sucrose in the colonization of S mutans strain 6715 in conventional Sprague-Dawley rats was studied. A diet with 56% sucrose favored the oral colonization of the test strain compared to diets with 56% glucose or fructose or to laboratory chow as determined by recoveries from extracted teeth ground in tissue grinders. S mutans strain 6715 cells became well established in all rats fed a high sucrose diet with cell inoculums ranging from 10(8) to the lowest effective dose of 10(5) CFU once orally administered; in rats on nonsucrose diets, inoculation with even the highest dose only infrequently resulted in the establishment of S mutans strain 6715. Sucrose- and glucose- grown cells appeared to behave similarly. Colonization of S mutans strain 6715 occurred in all rats fed diets with a sucrose content ranging from 56 to as low as 1%. The establishment of S mutans strain 6715 on the teeth of rats fed diets with a sucrose concentration of 0.1 or 0.01% was impaired and comparable to the diet containing 56% glucose. In rats fed a high glucose diet, uniform establishment and persistence of the test strain occurred after frequent inoculations with about 5 X 10(8) CFU. The colonization under these conditions appeared to be independent of the intestinal canal as a bacterial cell source. These data suggest the possibility that S mutans can establish itself in the human mouth in the absence of dietary sucrose. In rats fed a high glucose diet and inoculated with 10(7) CFU or less, the cells gradually disappeared from the teeth; in contrast, the test strain implanted well in rats fed the sucrose favors firmer attachment of initially weakly attached cells via in situ new glucan synthesis. S mutans strain 6715 also appeared to have some affinity for teeth in the absence of dietary sucrose that may be of ecological significance. Once firmly established in rats fed a high sucrose diet, S mutans strain 6715 maintained itself in high numbers on the teeth after a switch to a high glucose diet during a 14-week period.

Effect of a fluoride-containing chlorhexidine gel on bacteria in human plaque

The effect on the plaque flora of a fluoride-containing chlorhexidine gel in mouthpieces was studied in seven subjects. Use of the gel during a 3-month period resulted in a change in the pattern of sensitivity to cholorhexidine in the plaque flora as displayed by determination of the minimal inhibitory amount (MIA) of the drug in agar diffusion assays. Three months after the use of gel was discontinued, the MIA value for plaque bacteria had returned to its original level. The relative proportions of S. mutans and S. sanguis in plaque changed during the chlorhexidine period. Thus S. mutans could not be detected in plaque samples after 3-month use of the gel, and the frequency of S. sanguis was altered.