You can read part 5 of most common disease before reading part 6.
Susceptibility Of Teeth To Caries
Teeth may be resistant to decay because of factors affecting the structure of the tooth during formation. Serious efforts were made in the past to confirm the misguided belief that dental caries was due to hypocalcification of the teeth and was essentially a vitamin deficiency disease. This simplistic view of course ignored the extensive epidemiological findings that the best-nourished populations had the worst record for dental disease while poverty-stricken communities on deficient diets had a low caries prevalence, as discussed earlier.
Hereditary hypoplasia or hypocalcification of the teeth in which there are severe disturbances of structure are also not particularly susceptible to caries and there is no evidence that the degree of calcification of the teeth affects their resistance to caries. However, newly erupted teeth are generally caries susceptible, apparently because of a hypomineralized enamel structure which is made progressively less vulnerable by deposition of materials from saliva.
Factors Determining The Cariogenicity of Sucrose
- Sucrose forms up to a third of the carbohydrate content of many persons’ diets
- It promotes colonization of teeth by Streptococcus mutans
- Its disaccharide bond alone contains enough energy to react with bacterial enzymes to form extracellular dextran matrix
- Its small molecule allows it to diffuse readily into plaque
- Bacterial metabolism of sucrose is rapid
Effects of Fluorides
Fluorides from drinking water and other sources, are taken up by calcifying tissues during development. When the fluoride content of the water is 1 ppm or more the incidence of caries declines substantially. Fluoride may affect caries activity by a variety of mechanisms. Exposure to fluoride during dental development affects the structure of the developing teeth. This is shown by mottling of the enamel produced by excessive levels of fluoride. However, it is believed that the lower incidence of dental caries where water is fluoridated is due to its continued environmental effect on the teeth to reduce solubility of the enamel and promote remineralization. These effects may be more important than the effect of fluoride on structure.
Actions of Fluoride on Dental Caries
- Fluoride is incorporated into the teeth during development
- Fluoride acts mainly after eruption in early lesions by reducing enamel solubility and favoring remineralization
- A constant supply of small amounts of fluoride is most effective in reducing dental caries
- Floride may reduce acid generation in plaque
Fluoride is the only nutrient which has been proved to have this protective action. Despite the difficulties in distinguishing the degree of resistance of the teeth from the virulence of their cariogenic environment, it has become clear that fluorides have had a major impact on caries prevalence. There has undoubtedly been a significant decline in the prevalence of dental caries in countries where drinking water has been fluoridated. In Britain, as a result of widespread use of fluoridized dentifrices, there has also been so great a decrease in the disease as significantly to affect the nature of dental practice. These changes cannot be related to any comparable decline in sucrose consumption.