5. What Role Does Fluoride Play In Preventing Tooth Decay?

Question Suivante

5. What role does fluoride play in preventing tooth decay?

The SCHER opinion states:

Mechanism of fluoride action in caries prevention

Fluoride treatment regimens have been developed to prevent dental caries. Systemic fluoride is easily absorbed and is taken up into the enamel during the period of pre- eruptive tooth formation. The predominant beneficial cariostatic effects of fluoride in erupted teeth occur locally at the tooth surface. This could be achieved by fluoridated toothpaste, fluoride-containing water, fluoridated salt, etc. maintaining elevated intra- oral fluoride levels of the teeth, dental biofilm and saliva throughout the day.

Dental health and fluoridation

Figure 2 indicates that independent of the fluoridation policies across the EU Member States, there has been a consistent decline over time in tooth decay in 12 year old children from the mid-1970s, regardless of whether drinking water, milk or salt are fluoridated.

Figure 2 – Trends in tooth decay in 12 year olds in European Union countries (from Cheng et al. 2007).

It should be noted that there is a probable error regarding the figures from Germany because the data were collected during the unification period. Moreover water fluoridation was not practised in West Germany, and in East Germany only in certain regions and intermittently. Therefore, Germany should be placed under “no water- fluoridation”.

A vast number of clinical studies have confirmed that topical fluoride treatment in the form of fluoridated toothpaste has a significant cariostatic effect. Other preventive regimens include fluoride supplement and fluoridated salt given during the period of tooth formation. In the 1970s, fluoridation of community drinking water, aimed at a particular section of the population, namely children, was a crude but useful public health measure of systemic fluoride treatment. However, the caries preventive effect of systemic fluoride treatment is rather poor (Ismael and Hasson 2008).

In countries not using water fluoridation, improved dental health can be interpreted as the result of the introduction of topical fluoride preventive treatment (fluoridated toothpaste or mouth rinse, or fluoride treatments within the dental clinic). Other preventive regimens include fluoride supplements, fluoridated salt, improved oral hygiene, changes in nutrition or care system practices, or any change that may result from improved wealth and education in these countries. This suggests that water fluoridation plays a relatively minor role in the improvement of dental health.

The role of fluoride on dental health has been demonstrated by comparing the efficiency of naturally occurring low and high fluoride concentrations in tap water to prevent dental caries. A recent study showed an inverse association between fluoride concentration in non-fluoridated drinking water and dental caries in both primary and permanent teeth in Denmark. The risk was reduced by approximately 20% at the lowest level of fluoride exposure (0.125-0.25 mg/L) compared to less than 0.125 mg, and the reduction was approximately 50% at the highest level of fluoride exposure (more than 1.0 mg/L) (Kirkeskov et al. 2010). The data were adjusted for socio-economic factors.

Water fluoridation

Water fluoridation was considered likely to have a beneficial effect, but the range could be anywhere from a substantial benefit to a slight risk to children's teeth with a narrow margin between achieving the maximal beneficial effects of fluoride in caries prevention and the adverse effects of dental fluorosis (McDonagh et al. 2000).

The available evidence suggests that fluoridation of drinking water reduces caries prevalence, both as measured by the proportion of children who are caries free and by the mean change in dmft/DMFT score (decayed, missing and filled deciduous –dfmt– or permanent –DFMT– teeth)1. The studies were of moderate quality (UK-CRD 2003), supported by a Canadian review (Locker 1999), with the addition that the effect tends to be more pronounced in the deciduous dentition. The few studies of water fluoridation discontinuation do not suggest significant increases in dental caries.

The effect of water fluoridation tends to be maximized among children from the lower socio-economic groups, so that this section of the population may be the prime beneficiary. There appears to be some evidence that water fluoridation reduces the inequalities in dental health across social classes in 5 and 12 year-olds, using the dmft/DMFT measure. This effect was not seen in the proportion of caries-free children among 5 year-olds (McDonagh et al. 2000). In a recent review, Health Canada has concluded that the optimal concentration of fluoride in drinking water for dental health was 0.7 mg/L (http://www.hc-sc.gc.ca/ewh-semt/alt_formats/hecs- sesc/pdf/consult/_2009/fluoride-fluorure/consult_fluor_water-eau-eng.pdf).

In a study of students (16-year olds) living on the border between the Republic of Ireland (fluoridated water) and Northern Ireland (non-fluoridated water) it was found that some of the variance in decay experience among the adolescents was explained by parental employment status. The higher decay experience in lower socio-economic groups was more evident within the non-fluoridated group, suggesting that water fluoridation had reduced oral health disparities (CAWT 2008). Similarly, Truman et al. (2002) and Parnell et al. (2009) concluded that water fluoridation is effective in reducing the cumulative experience of dental caries within communities, and that the effect of water fluoridation tends to be maximized among children from the lower socio-economic groups. Furthermore water fluoridation offers additional benefits over alternative topical methods because its effect does not depend on individual compliance.

The benefits of water fluoridation for adult and elderly populations in terms of reductions in coronal and root decay are limited (Seppä et al. 2000a, Seppä et al. 2000b).

Fluoridated foods and dietary supplements

There is no consistent information on the efficiency of fluoridated milk compared with non-fluoridated milk on dental health. For permanent teeth, after 3 years there was a significant reduction in the prevalence of DMFT (78.4%, p