Dental caries is a multifactorial disorder, the initiation and progression of which are affected by factors related to host susceptibility, oral microflora, and diet. Interlocking triple rings are frequently employed to demonstrate that microorganisms, fermentable carbohydrates, and a susceptible tooth surface are all requisite in the caries process. It is well established that lesions do not develop in gnotobiotic animals and that dietary modification such as carbohydrate restriction significantly restricts caries activity. There is a paucity of knowledge on the effect of specific environmental factors on caries incidence.In an earlier study (1 ) it was found that lighting significantly affected caries incidence in the golden hamster. These animals were fed a diet containing 61% sucrose over a 15-week period. Under these conditions carious breakdown was very extensive and in many cases the crowns were virtually destroyed. The authors pointed out that this overwhelming involvement may have caused a loss of masticatory ability resulting in reduced chewing, ingestion, and absorption of food.There was thus a need for the testing of the effects of light on caries incidence in a more sensitive model with a much less advanced state of destruction induced. Such a model has been developed for caries evaluation in which the cotton rat (Sigmodon hispidus) is weaned at 12 days of age and placed on a cariogenic diet (2). With a dietary sucrose level of approximately 6%,

While studying natural diets which were cariogenic to the cotton rat, Constant, Sievert, Phillips, and Elvehjem1 found that the degree of dental caries produced by an oatmeal diet was sharply decreased by the inclusion of finely ground oat hulls in the diet. The protective effect was greater at the 25 per cent level than at the 12.5 per cent level. Later work by Taketa and Phillips2 demonstrated that oat hulls were also protective in a semipurified diet at both 25 and 10 per cent levels. These workers furnished evidence suggesting that the protective effect was due neither to a brushing or abrasive action by the hulls nor to a dilution of the cariogenic diet by the hulls. They also verified an earlier observation by Constant et al.1 that the ash portion of the hulls was not anticariogenic. Jenkins and Phillips3 showed that the crude fiber, hemicellulose, and lignin fractions of the hulls were devoid of anticariogenic activity. Taketa and Phillips2 found that the greatest activity was located in an ethanol-soluble fraction of the hulls, which comprised less than 5 per cent of their weight. Some activity remained in the residue; however, later studies4 showed that extraction with ammoniacal ethanol removed activity that was not removed by ethanol alone.The activity in the ethanol extract not only was effective in the inhibition of dental caries but was also capable of inhibiting the growth of organisms isolated from the carious cotton rat tooth.5 This observation, coupled with the fact that a pure culture of Lactobacillus acidophilus var. Farr was inhibited by the extracted solids, indicated that the anticariogenic activity of oat hulls was related to an alteration in the oral flora of the cotton rat. Using L. acidophilus as an assay organism for oat-hull anticariogenic factors, Taketa and Phillips5 found the active factors to be acidic in nature and perhaps to be certain phenolic acids and palmitic acid.Madsen4 assayed other seed hulls for their anticariogenic activity by feeding them in an oatmeal diet at the 25 per cent level. It was found that, in addition to oat hulls, the hulls of rice and peanuts were also effective and reduced the incidence of caries by about 75 per cent; the hulls of cottonseed and barley reduced the incidence by about 35 per cent. Madsen also demonstrated that the acidic fraction prepared from ethanol extracts of these hulls was effective as a growth inhibitor of L. acidophilus var. Farr.Subsequent studies demonstrated that oat hulls were also anticariogenic in the diet of the albino rat. Madsen4 found them to be anticariogenic when fed in a semipurified diet to the Harvard strain of caries-susceptible rats. Buttner and Muhler6 demonstrated

The effects of nutritive losses incurred by heating certain milk proteins have been comprehensively reviewed by Griswold.' Subsequently, Fairbanks and Mitchell2 have found that the biological value of skim-milk proteins decreased according to the severity of heat treatment during processing and that supplemental lysine and cystine improved the value of the heat-damaged protein. More recently, Kraft and Morgan3 have demonstrated that the loss in growth-promoting efficiency for rats of autoclaved skim-milk powder could be restored to nearly normal levels by lysine supplementation. McClure and Folk4 have shown that the loss of nutritive value resulting from autoclaving the skim-milk powder used in a cariogenic diet was accompanied by a striking increase in smooth-surface dental caries in rats. Supplementation of the autoclaved milk with L-lysine enhanced growth and decreased caries (McClure and Folk5). Their findings have suggested that the cariostatic effect of L-lysine was related to its deficiency in the diet. The relationship of lysine to growth and caries has appeared to be an indirect one, since a diet containing non-autoclaved skim-milk powder, presumably adequate in lysine, produced caries not clearly inhibited by additional L-lysine.McClure6 has studied the mechanism whereby lysine inhibited caries and found that supplemental lysine in the diet, in the water, or by stomach intubation decreased caries. Intraperitoneal injections of lysine increased growth but were not clearly effective against caries. These observations have suggested that lysine acted extraorally in the digestive tract. Wasserman, Comar, and NoldT have shown that lysine and lactose, both known to be affected by autoclaving skim-milk powders, increased the gastrointestinal absorption of Ca45. Observations by Haldi, Wynn, JBentley, and Law8 and McClure, Folk, and Rust9 have shown that caries was inhibited by increasing either the calcium or the phosphorus content in the diet8 and that the incidence of caries was affected by the levels of calcium in the autoclaved skim-milk-powder diet.9 All these observations have suggested the possibility that calcium and phosphorus may be involved in the anticariogenic action of lysine.A preliminary study in our laboratory of the effects of autoclaved milk powder and lysine on rats indicated that the relationship of lysine to growth and dental caries would be more apparent if the sexes were studied separately. An objective of the present study, therefore, was to determine the effects of supplemental lysine on growth and

The ability to wean cotton rats satisfactorily at 12 days of age (K. 0. Madsen and E. J. Edmonds, J. dent. Res., 42:867-73, 1963) has provided a convenient means for studying the influence of dietary factors on dental caries when they are provided at various stages of molar tooth development. Sodium fluoride, incorporated in an oatmeal cariogenic diet and fed for only 2-3 days immediately after the eruption of the respective molars, has been found to reduce dental caries significantly (K. 0. Madsen and E. J. Edmonds, Fed. Proc., 22:553, 1963). Fluoride, fed at 45 ppm in the diet from the twelfth through the fourteenth day, significantly protected first molars, which erupt from 7 to 12 days of age, but had no effect on second molars, which erupt from 12 to 20 days of age. With an ad libitum feeding regimen, it is difficult to determine accurately the amount of fluoride ingested by the rats during the 3-day experimental period. The purpose of the present study was to determine whether fluoride administered in controlled amounts of 0.1 per cent solution for short periods would reduce dental caries as it does when incorporated in the diet fed ad libitum.The rats were weaned at 12 days of age, and littermates were divided into 2 groups. Both groups were housed in individual wire cages and provided with water and the oatmeal cariogenic diet ad libitum. The control group was supplemented with 2 drops of distilled water every hour 8 times daily for 3 days after weaning. The experimental group was supplemented in the same manner with 2 drops (0.1 ml.) of 0.1 per cent NaF. This amount of NaF solution provided a measured amount of fluoride about equal to that estimated to be normally consumed daily in a diet containing 45 ppm fluoride. The rats were sacrificed at 40 days of age and the teeth scored for fissure caries (

In a recent review of caries-inhibiting agents, Shawl has described and evaluated the procedures developed for experimental caries research. In general, it is useful to evaluate the anticariogenicity of a substance by incorporating it into a cariogenic diet that is fed to weanling caries-susceptible rodents. After a sufficient time for caries development in the control group, the caries inhibition by the test substance is measured.A compilation by Hein2 of a large number of assays for anticariogenic agents has indicated that, in most cases, the test substance was fed for the entire experimental period of about 100 days or more. In other studies animals were fed the test substance for a prolonged period, although for less than the experimental period. McClure3 has found a prolonged reduction in caries when he fed 100 ppm of fluoride to 40-, 100-, and 200-day-old rats for 85, 60, and 40 days, respectively, and followed this procedure by a cariogenic diet for 100 days. Keyes4 has recently described a new method for assaying caries-inhibiting agents. In his procedure, caries was developed in weanling hamsters until they were 39 days of age. They were then fed penicillin in the diet for 54 days. Penicillin was then removed, and the cariogenic diet was fed for an additional 50 days. Since the third molars had erupted between 35 and 40 days of age, all three molars received a prolonged treatment with the test substance.