Beyond the classical Hopewood and Vipeholm studies, data on cariogenicity of foods in humans are sparse. It is not practical to subject the myriads of foods developed by new technological processes to clinical trials. We have to rely upon epidemiological studies, laboratory data, dental plaque studies, nutritional and dietary surveys and other relevant data in order to define cariogenic determinants of food. We shall now synthesize a large volume of information, often inadequate, in order to determine the main dietary constituent(s), dietary properties and patterns of food consumption that are associated with dental caries.
The four carbohydrates starch, sucrose, fructose and glucose comprise the greatest proportion of foods consumed by man. The main polysaccharide (starch) is not highly cariogenic in animals or man at least in some circumstances. Populations in countries such as Japan and ltaly are known to consume large amounts of starch in the form of rice, macaroni and spaghetti, but their caries rates are relatively low. On the other hand, controled studies in experimental animals and in humans have confirmed that excessive and frequent use of highly fermentable mono- and disaccharides is correlated with high caries rates. While glucose, fructose, lactose and mannose have been shown to be cariogenic in animal experiments they are usually minor constituents of human foods as they are present only in dried fruits, honey and milk. Sucrose is by far the commonest dietary sugar. In North America this single dietary item contributes to more than one half of the total carbohydrate consumed and because sucrose dominates dietary sugar, it is the carbohydrate most related to caries. Because of the significance of carbohydrates in caries this topic is devoted to a discussion of the patterns of consumption of carbohydrates in American diets and to the role of sucrose.
We know little about the significance of physical properties of foods and their effects on cariogenicity, since few studies involving human subject have been conducted to explore this relationship. Some important physical properties that determine food texture are. (1) Mechanical properties- hardness, cohesiveness, viscosity, adhesiveness, (2) geometric properties- particle size and shape, (3) others- moisture and fat content.
Texture of food and the subjective description of food items by the use of terms as soft – hard, crumble- brattle, tender- tough, sticky – gooey, gritty- coarse, dry- moist arise from their physical properties.
From a dental standpoint the physical properties of food may have significance by affecting food retention, food clearance, solubility and oral hygiene ( plaque reduction). The incorporation of dyes into toffee demonstrated the tenacious retention of candy on enamel surfaces. Adhesive properties of food have been measured and correlated with their retention in the mouth after ingestion.
The high fibrous, cellulose content of plant food exerts a mechanical cleansing action on teeth and eating of raw fruits and vegetables has long been recommended as an aid to oral hygiene and also as a caries preventive measures. Clinical studies have not confirmed that physical parameters are as important as the frequency of eating, in determining cariogenicity of foods. A study on the effect of apples and dental health gave indication of caries reduction, but initial differences in caries score of the ‘control’ and ‘apple’ group made comparisons more difficult . Other fibrous vegetables as raw carrots and celery also expert mechanical cleaning effects, and are not as strongly acidic as apples. A clinical study in which carrots were eaten after the midday meal did not result in a significant reduction in caries in schoolchildren. On the other hand, addition of water to an experimental animals diet, or modification of particle size of a diet, is known to induce significant effects on caries in animals.
The physical texture and chemical composition of food is known to effect salivary flow rates. Saliva that is rapidly flowing is more alkaline than resting saliva and more supersaturated with calcium and phosphate, and thus may be more caries- inhibitory.
Physical properties of food, particularly those that improve the cleaning action and reduce the retention of food within the oral cavity and increase saliva flow, are to be encouraged in everyday diets. However, clinical evidence that consumption of these food items will significantly reduce caries incidence is lacking.
The concept that natural, unrefined foods contain protective factors against dental caries has long been expounded. The idea originated with experiments which indicated that saliva incubated with refined foods caused a greater dissolution of tooth enamel than when incubated with unrefined foods mixtures that included bran wheat germ and unrefined treacle and cane juice contained protective factors. The protective substance in the studies with cereals was identified as phytate- a polyphosphate. Phytate when applied to tooth enamel reduces its solubility and has caries- inhibiting effects when added to animals diets but its effects on caries in man has not been tested.
Some dietary items are highly acidic and therefore affect, usually in a transient manner, the pH in plaque and saliva. Natural foods, such as lemons, apples, fruit juices and carbonated beverages, are sufficiently acidic as to cause demineralization of enamel that is in prolonged contract with them. These items, under normal dietary use, are of no consequence in the dental caries process. However, excessive (habitual) use of these foods and beverages may causes etching of enamel with cavitation. Reports of excessive frequency of consumption of carbonated beverages, having a low pH, and continuous chewing or habitual sucking of lemons as a cause of dental erosion are well documented. Thus, habitual use of highly acidic foods should be discouraged.
Distinction should be made between destruction of teeth be a carious process and dissolution of enamel by chemical erosion. In the former process, the production of acids by bacteria acting on a substrate is essential, in the latter, enamel is dissolved by excessive and frequent contact with ingested fluids of low pH ( usually below 4)
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