You can read the part 3 of most common disease that causes loss of teeth, before reading the 4th part.
Sucrose as a Plaque Substrate
Direct measurement of pH changes in the mouth shows that there is intermittent acid production on the surface of the teeth and this follows the pattern shown earlier in the Stephan curves. Ingestion of sucrose leads to a burst of activity in the plaque so that the pH may fall low enough to attack enamel before slowly returning to the resting level. The frequency with which substrate is made available to the plaque is therefore important. When sucrose is taken as a sweet drink, any surplus, beyond the capacity of the organisms in the plaque to metabolize at the time, is washed away. If sucrose-containing drinks are taken repeatedly at short intervals, the supply of substrate to the bacteria can be sufficiently frequently renewed to cause acid in the plaque to remain persistently at a destructive level.
A similar effect may be caused by carbohydrate in sticky form, such as a caramel, which clings to the teeth and is slowly dissolved, releasing substrate over a long period. The effects of maintaining plaque activity by repeated administration of small quantities of sucrose have been demonstrated by the use of animal feeding devices to dispense metered quantities of sucrose in diets at fixed intervals. These show that a given amount of sucrose is more cariogenic when fed in small increments, but at intervals to maintain maximal plaque activity, than the same amount fed as a single dose.
Effects of Sucrose on Plaque Polysaccharide Production
As discussed earlier, the cariogenicity of plaque depends on its ability to adhere to the teeth, to resist dissolution by saliva and its protection of bacterial acids from salivary buffering. These properties depend on the formation of insoluble polysaccharides produced particularly by cariogenic strains of S. mutans.
Effects of Sucrose on the Oral Microbial Flora
Colonization by cariogenic bacteria, especially S. mutans, is highly dependent on the sucrose content of the diet. In the absence of sucrose, S. mutans cannot usually be made to colonize the mouths of experimental animals. In humans, the plaque counts of S. mutans also appear to depend on the sucrose content of the diet. Severe reduction in dietary sucrose causes S. mutans to decline in numbers or disappear from plaque.
Dental caries has been most prevalent in well-nourished, Westernized communities, such as Britain, the USA and others with similar lifestyles where large quantities of sucrose, particularly in the form of sweets or snack bars, are eaten. In the past particularly, there have been many studies of poor communities living on traditional diets with little or no sucrose content. A low prevalence of caries has been shown in parts of China and of Africa, the Seychelles, Tristan da Cunha, Alaska and Greenland. Many studies were carried out on Eskimo races who were caries-free when consuming their traditional diet of seal or whale meat, and fish. Similarly in South African races, despite a high-starch carbohydrate diet, caries was found in fewer than 9% of those examined, but greatly increased when there was access to a modern diet.
In such studies no association has been found between malnutrition and caries. Generally the reverse is true, and, when nutrition is poor, caries is infrequent. These diets also vary widely in content, from rice as the staple in China or coarsely ground cereals in Africa to a mainly meat and fish diet among Eskimos. The common feature of these diets, and one differentiating them sharply from Westernized diets, is low or negligible consumption of sucrose.