By Dr Senani Wijesena 29/07/2016
It is important to note that while fluoride contributes to the remineralisation process in the enamel of the tooth surface this is not dependent on fluoride, and that fluoride’s anti-caries effect is critically dependent on calcium and magnesium content of teeth enamel. Among young individuals with low calcium and magnesium in teeth enamel (usually due to under-nutrition), fluoride ingestion and contact with teeth present as hypo-calcification and/or hypoplasia (under development), which may paradoxically make such individuals more vulnerable to dental caries.
Caries is caused by the dissolution of the teeth by acid produced by the metabolism of dietary carbohydrates by oral bacteria. These bacteria are primarily Streptococcus Mutans and Lactobacilli. Fluoride, in addition to forming erosion resistant fluoroapatite in teeth, has been shown to inhibit bacteria that cause dental caries. This is thought to occur mainly through inhibition of energy metabolism (glycolysis) in caries causing microorganisms such as Streptococcus mutans.
Many factors, however, contribute to the development of dental caries including quantity of saliva, oral hygiene, nutritional status, and immune function. If these factors are compromised, adding fluoride has limited effect on preventing dental caries. Salivary secretions help neutralise caries-causing acids and contains calcium and phosphate that facilitate teeth remineralisation. Individuals with low salivary secretions have higher risk of dental caries.
Acid producing normal flora of the oral cavity such as Lactobacillus acidophilus thrive and may become cariogenic in the presence of high sugar intake as well as fermentable carbohydrates on the enamel as from carbonated soft drinks, lollies and starchy, refined carbohydrates (e.g. bread) respectively which are metabolized to acids by plaque bacteria. High carbohydrate diets therefore are a major factor in the development of caries. This is also due to the presence of the digestive enzyme, salivary amylase which breakdown starches (carbohydrates) in the mouth into smaller sugars that can then act on eroding teeth enamel.
In addition, low anti-oxidant levels (low vitamin C, A), low vitamin D, niacin (vitamin B3) and inflammation increase risk of gingivitis, poor tooth formation and associated teeth problems. Vitamin D, for example, increases calcium deposition in teeth and bones and induces cathelicidin, an antimicrobial peptide, which attacks oral bacteria linked to dental caries. Hence, deficiency of these nutrients may contribute to the development of dental caries.
Thus, the multiple pathways to the development of dental caries make it difficult to accurately ascertain the contribution of fluoride ingestion to dental caries prevention. Given that the action of fluoride on dental caries prevention is topical, only topical fluoride products are likely to provide optimal benefits claimed for this chemical. Improvements in oral hygiene, nutrition and public health over the last 60 years has been the primary reason dental caries rates has decreased world-wide and not due to water fluoridation.
