Caries activity induced by frequency--controlled feeding of diets containing sucrose or bread to Osborne-Mendel rats

Rodent model in caries research

The rodent model of dental caries has made fundamental contributions to the understanding of the etiology, pathogenesis, and prevention of this disease. In conducting animal-based investigations, important details considered essential for successful outcome are occasionally overlooked. Adequate number of animals of appropriate age should always be included to ensure sufficient statistical power to draw valid conclusions. Attention should be paid to litter source as it is clear that litter origin may have a profound effect on the outcome. Inclusion of additive in diet may also affect eating pattern. A range of special techniques are available which can expand the role of animals in exploring the pathogenesis of dental caries. The arrival of genetically altered microorganisms along with availability of knock-out rodents offers exciting challenges to further explore the pathogenesis of this still too common disease.

Demineralization of dentin by Streptococcus mutans biofilms grown in the constant depth film fermentor

To develop a bacterial demineralization model, we grew Streptococcus mutans biofilms in a constant depth film fermentor (CDFF) and studied the effects of sucrose pulsing frequency (SPF) in time on dentin demineralization. S. mutans biofilms were grown in dentin specimens with grooves and on dentin surface specimens for 20 days. During the experiments, 2% sucrose was pulsed either 4 or 8 times per day for periods of 30 min. Diluted brain-heart infusion medium containing 25 mM PIPES buffer and 1.5 mM CaCl2 was pulsed as the alternative growth medium. Specimens with intact biofilms were taken out on days 5, 12 and 20. The model was assessed by viable counts of the biofilm, mineral loss and lesion depth in the dentin specimens (by transversal microradiography) and pH measurements in the groove (by pH microelectrode). The results showed that biofilms formed on the dentin surface specimens were constant in viable counts for the low SPF, while this parameter tended to increase with time under the high SPF. Lesions with intact surfaces were formed and the lesion size increased significantly over time and increased significantly with increasing SPF. Typical Stephan curves were found after sucrose pulsing. The pH inside the groove returned to neutral under low SPF, but remained below 6.5 under high SPF. With the CDFF S. mutans biofilm model, lesions can be created in dentin within reasonable experimental time periods, as a result of the presence of a biofilm and in response to carbohydrate challenges.

Dental considerations for dietary counselling

A decline in the prevalence of dental caries over three decades has occurred without a significant change in the consumption of fermentable carbohydrates, indicating that good dental health is achievable with the presence of cariogenic factors in the diet. Since, in many countries 80% of the caries is present in only 20% of the population, 'targeted intervention' would seem a better preventive option, stressing the judicious use of fluoride, plaque control, fissure sealants and a sensible diet. Dietary modification is notoriously difficult to achieve, being incumbent upon the subject's willingness to effect a change in behaviour. Many texts refer to the frequency of consumption of carbohydrates as being all-important, recommending a reduction in the frequency. However, recent evidence suggests it is the frequency of toothbrushing with a fluoride containing dentifrice which is of fundamental importance in promoting remineralisation of enamel. Dietary advice should be formulated which is both realistic and positive. Trying to dissuade children from consuming products, which they perceive to be tasty and pleasurable is counter productive and more emphasis should be given to tooth brushing using a fluoride toothpaste. Also, a fundamental shift away from the idea of 'good foods versus bad foods' is required and more emphasis laid on good diets as opposed to bad diets. Children should be able to enjoy foods traditionally considered 'bad' from a dental viewpoint, as long as they brush their teeth with a fluoride containing dentifrice and have a sensible approach to their consumption.

Enamel demineralization in situ with various frequencies of carbohydrate consumption with and without fluoride toothpaste

There is little information in the literature on the relationship among the frequency of carbohydrate consumption, the use of fluoride toothpaste, and enamel demineralization. The aim of this investigation was to compare the extent of demineralization of enamel slabs in situ, with a sugar-based solution, consumed in constant amounts but with various frequencies in subjects both with and without the use of fluoride (F) toothpaste. Eight subjects wore removable mandibular appliances carrying an enamel slab cut from white-spot lesions. The subjects were required to drink 500 mL of a 120-gm/L sugar solution either once, 3, 5, 7, or 10 times/day for 30 sec on each occasion, for a period of 5 days while brushing their teeth twice daily with either a F (1450 ppm NaF) or a F-free toothpaste. Mineral analysis revealed that when the subjects used a F toothpaste, net demineralization was evident only with the seven- and 10-times/day regime (ns). When F-free toothpaste was used, statistically significant demineralization was observed when the frequency exceeded 3 times/day. This study demonstrates the importance of F-containing toothpaste in enamel re-/demineralization by varying the frequency of carbohydrate challenge

Effects of dietary sucrose levels on pH fall and acid-anion profile in human dental plaque after a starch mouth-rinse

The effects on the metabolism of starch by plaques formed in human subjects during periods of dietary sucrose limitation or supplementation were studied. High sucrose (HS) plaques showed lower resting pH and pH minima, and higher concentrations of lactate ion after the starch mouth-rinse than low sucrose (LS) plaques. Plaque samples incubated with starch solutions in vitro showed no differences in final pH or acid-anion concentrations between HS and LS diets. Plaque-amylase activity was higher on HS than LS diets. Thus starch was more acidogenic when consumed as part of a diet already rich in sucrose, but it is unclear whether this was a specific or non-specific effect of starch on plaque metabolism.

The establishment of the bacterium Streptococcus mutans in dental plaque and the induction of caries in macaque monkeys (Macaca fascicularis) fed a diet containing cooked-wheat flour

A diet containing 50.7 per cent cooked wheat flour (78 per cent starches and dextrin) was fed to 82 monkeys from weaning for up to 407 days. Streptococcus mutans became established naturally and remained at a high level (25-40 per cent of the total anaerobic colony count) in the dental plaque of the majority of animals but in only 2 were carious lesions detected. The predominant Strep. mutans serotypes isolated from plaque were c, e and h, which produced acid when incubated with the diet in vitro. Twenty-five monkeys were switched to a cariogenic high sucrose diet, and 6 months later 72 per cent of them had carious lesions (mean +/- SD = 6.5 +/- 6.6 carious lesions per monkey). The failure of the starch diet to promote tooth decay in monkeys supports the general conclusion that starch and starch products are virtually non-cariogenic for man.

Duration of response and stimulus sequence in the interpretation of plaque pH data

Evaluation of cariogenicity from evidence provided by plaque pH data may be assisted if the duration as well as the extent of the pH fall is examined. Consumption of foods in sequence may alter the pH response to individual items.

Human interdental plaque-pH data and rat caries tests: results with the same substances

Interdental plaque-pH telemetry measures, in vivo, H-ion concentration at the level of the enamel surface under an undisturbed layer of plaque. It is better suited to test non- or hypo-acidogenic products than are rat caries tests. These products can, with a very high probability, be considered non- or hypocariogenic ("safe, or friendly, for teeth"), no matter how frequently they are consumed. Plaque-pH telemetry is poorly suited for judging the effectiveness of agents directed at enamel - e.g., topical fluoride, remineralizing solutions, etc. - or agents which may have long-term effects on plaque composition. Plaque-pH telemetry is able to demonstrate the effects of different meal patterns and the form and texture of foods on oral clearance and plaque pH.

The cariogenicity of snack foods and confections

A survey of the relationship between caries prevalence and the consumption of sugar and other foods by man has been interpreted to show that snack foods share importance with sucrose in caries causation. Support for this conclusion is found in animal experiments and some in vitro and in vivo tests.

Dental caries: prospects for prevention

Combined utilization of measures now available or imminent could reduce caries of the crowns of the teeth to the point of negligibility as a public health problem, if public desire were great enough to motivate changes in some of our habits (64). Universal optimum application of fluoride and substitution of starchy foods for sugary ones (or even simply judicious consumption of sugar) would alone do most of the job. Sealing of susceptible occlusal areas with adhesive polymers promises to protect the sites where fluoride evidently cannot be maximally effective. It seems unlikely that any single measure will be found sufficient to control this multifactorial disease. Consequently, we must continue the search for new means to increase the caries resistance of teeth, to reduce the cariogenicity of foodstuffs, and to check the deleterious activities of cariogenic bacteria. Anticaries food additives and antibacterial agents for intraoral use seem to be approaching practicability. Past performance warrants expectation that ongoing fundamental investigations will produce leads for future development and application.