Here is classic study that fluoride advocates point to as “proof” that water fluoridation is good for everyone. The results of the study show that there are indeed differences between these areas. Whether the differences in dental health can be attributed to the fluoride concentration is another question altogether. There are several difficulties with relying on this study and those like it of the past to make the attributions claimed by the authors. “Pro-fluoride” advocates have convinced themselves that fluoridation is good by interpreting and applying study results inappropriately Here are a few thoughts to consider:
1. The study design itself is hypothesis generating. A causal attribution to fluoride for the differences between these areas is unsupported simply because of the methodology.
2. Children and people are not statistical categories. Application of statistical categories masks negative effects on any particular individual.
3. Studies such as this that have found contrary results (no significant differences) are typically not publishable. This is a well-known reality — publication bias. Yet negative studies are equally as important as this study. Further, there is a very large literature base of toxicity studies on fluoride that should inform the interpretation of any study.
4. A single metric is applied to characterize “dental health”. Confidence limits for the analysis of the raw observations are not reported. A single number metric masks any underlying variability in raw data. What are the 95% confidence intervals on these observations? A particular statistical test may or may not indicate significance depending upon how the raw data are “cut” or “homogenized.” This is simply a basic question that should be asked of any study.
5. Not withstanding the competence of the professionals involved, quality control of the dental examinations as reported is very limited if not inadequate. An objective measure or test of consistency between observers was need at the time of the study. Even very good professionals will disagree on an observation and/or a diagnosis. This is simply a fact and is not intended to be a criticism of anyone involved in the study. Such inevitable differences are not addressed in the article beyond citing “credentials” and experience. “Credentials” and experience are indeed very important. But even as impressive as they are in this case they do not substitute for objective quality control measures to demonstrate observational consistency between observers.
We’ve simply repeated the cycle of the past. Inappropriate attributions are made to promote the addition of fluoride to drinking water. Those who advocate fluoride are usually mystified that anyone would oppose addition of fluoride to drinking water. Yet the study is inadequate to make the attributions argued by pro-fluoride advocates. In the end, fluoride advocate interpretations and attributions are simply a reflection of what has been assumed from the beginning. The study provides no new objective evidence nor any new compelling arguments to support intentional addition of fluoride to a person’s drinking water.
Blinkhorn AS, Byun R, Johnson G, Metha P, Kay M, Lewis P. The Dental Health of primary school children living in fluoridated, pre-fluoridated and non-fluoridated communities in New South Wales, Australia. BMC Oral Health. 2015 Jan 21;15(1):9.
BACKGROUND: The Local Government Area of Gosford implemented a water fluoridation scheme in 2008. Therefore the opportunity was taken to record the dental health of primary school children aged 5-7 years prior to the fluoridation and compare the results with other communities in NSW with different access to fluoridated water. The aim was to compare the oral health of New South Wales (Australia)s 5-7 year olds living in fluoridated, and non- fluoridated communities. One of the areas was due to implement water fluoridation and is termed the pre-fluoridation site.
METHODS: Pupils in the first year of Public and Catholic Schools in three areas of NSW were recruited. Class lists were used to draw a sample of approximately 900 per area. This number allowed for a non-response rate of up to 30 per cent and would give a sample sufficient numbers to allow statistical inferences to be drawn. Children whose parents consented received a dental examination and the clinical data was collected on mark sense cards.
RESULTS: In the 3 areas the proportion of children who received a dental examination varied; 77.5% (n = 825) for the fluoridated area, 80.1% (n = 781) for the pre-fluoridated area and 55.3% (n = 523) for the non-fluoridated area. The mean dmft was 1.40 for the fluoridated area, 2.02 for the pre-fluoridated area and 2.09 for the non-fluoridated area. These differences were statistically significant (p < 0.01). Differences were also noted in the proportion of children who were caries free, 62.6% fluoridated area, 50.8% for the pre-fluoride area and 48.6% for the non-fluoride location.
CONCLUSION: The children living in the well-established fluoridated area had less dental caries and a higher proportion free from disease when compared with the other two areas which were not fluoridated. Fluoridation demonstrated a clear benefit in terms of better oral health for young children.
Click here for paper (Open Access).