Heather Hill DDS, MBI
Water fluoridation, milk fluoridation, single agent topical fluoride and combination topical fluoride effectively prevent/reduce caries.
There is ample evidence that water, milk, and topical fluoride interventions are beneficial in preventing/reducing caries, and limited evidence that they do not result in adverse aesthetic, fracture or cancer outcomes.
What are the efficacy outcomes (measured by caries reduction) and harms (dental fluorosis, fracture, cancer and “other adverse effects”) of a) water fluoridation b) milk fluoridation, c) salt fluoridation, d) topical fluorides (including chewable tablets, chewing gum tables, drops, gel, mouthrinse, toothpaste and varnish) and e) combinations of topical fluorides?
The authors searched 4 databases for articles published between 1996 and December 2006. A total of 5418 titles and abstracts were identified. The intent was to update the organization’s previous clinical question/evidence summaries of the findings with information from existing systematic reviews. After the abstracts were evaluated by 3 reviewers (1/3 each) full-text analysis was performed (1/3 each) on 408 articles resulting in 77 citations that met the criteria. The inclusion and exclusion criteria were explicit. For each clinical question the “highest available level of evidence” was assessed. Outcome measures included attributable risk, dmfs/t, DMFS/T, incidence of fluorosis of aesthetic concern and other adverse events.
The updated review presented good evidence that water fluoridation increases the proportion of caries-free children [adjusted pooled mean difference, 14.3, 95% CI 6.7, 2.1)], and decreasing dmft/DMFT scores [adjusted pooled mean difference, 2.61, 95% CI, 2.31, 2.91]. There is good evidence that milk fluoridation plays a significant role in the prevention/reduction of caries. No studies addressing salt fluoridation met the inclusion criteria. There is good evidence that topical fluorides effectively reduce caries incidence. There is good evidence “some combination of topical agents may be more effective at preventing/reducing caries than single agents.” There is limited evidence that water fluoridation does not result in the development of fluorosis of ‘aesthetic concern.’ There is good evidence optimal water fluoridation has little protective or deleterious effect on fracture risk. The review offered a summary of limited evidence that no statistically significant relationship exists between water fluoridation and the risk of cancer. There is poor evidence to reach a conclusion about other possible “negative effects of water fluoridation.” There is poor evidence to determine any impact of milk fluoridation, salt fluoridation, or topical fluoridation on fluorosis, cancer risk, osteoporosis or impact fracture risk, or other harms.
The benefits of water fluoridation, and to a lesser extent milk fluoridation, are well supported by the evidence. The benefits of single and combination topical fluoride supplementation are clear but which combination is most beneficial is unclear from the studies. There is only limited evidence evaluating potential harms of fluoride interventions, none of which identifies any concerns.
Source of Funding:
Australian National Health and Medical Research Council.
Importance and Context:
The Centers for Disease Control and Prevention has identified community water fluoridation as one of the 10 great public health achievements of the 20th century. Because of the wide variety of different individual and public fluoride interventions, dental professionals should remain informed about fluoride efficacy and safety research.
Strengths and Weaknesses of the Systematic Review:
The search was limited to English-language publications, which may bias the findings. Safety and efficacy outcomes were not defined. It is not clear whether study selection or data extraction were carried out independently or in duplicate. Some selection methods were incompletely described and posthoc limitations were made. For included studies brief descriptive data and a global quality rating were provided. The authors did not adhere to their explicit methodology “[w]here a higher level of evidence was available, lower levels would not be assessed.” As a result, studies with “lower levels” of evidence or those that did not meet the inclusion criteria were used to answer research questions (e.g. milk fluoridation in the prevention of caries, salt fluoridation in the prevention of caries, and dental fluorosis, etc.). The clinical question summaries did not provide the level of evidence of their included studies, nor the quantity of studies. Consequently, to learn this information, one must access additional tables and text. Fluoride supplementation such as bottled water, drops, chewable tablets, chewing gum, and food products processed in fluoridated communities, were not addressed.
Strengths and Weaknesses of the Evidence:
The main comparison for each question was made between fluoride versus no fluoride, except for the single versus combination topical fluoride intervention. Only the data from water fluoridation studies were pooled. Evidence of the benefit of milk fluoridation is emerging. Although there is wide heterogeneity in the combinations of topical fluoride interventions studies, the results show that combinations are more effective than single agents. There is a lack of good evidence regarding adverse outcomes because relevant studies are lacking. Also, there is no standardized definition of harm and control over confounding factors. Greater standardization of study design, outcomes and reporting would benefit both future trials and meta-analyses. There are no consistent good quality studies that compare the benefits and risks of different fluoride delivery systems.
Implications for Dental Practice:
Several fluoride interventions are available to clinicians and public health professionals. Community water fluoridation remains the most well studied and effective method of delivering fluoride. Combined topical fluoride interventions are more effective than a single agent topical fluoride. However, what combination of multiple interventions that provides the most effective benefit is unknown.