(Dr. Limeback was one of the 12 scientists who served on the National Academy of Sciences panel that issued the 2006 report, “Fluoride in Drinking Water: A Scientific Review of the EPA’s Standards.” Dr. Limeback is an associate professor of dentistry and head of the preventive dentistry program at the University of Toronto)

My Familiarity with South Island and NZ:

In 2003 I attended and presented a paper at the multi-day International Conference on Fluoridation held in Dunedin. I have also toured much of your beautiful South Island. As head of the preventative dentistry program at Toronto I maintain a close watch on all matters related to fluoridation which of course includes New Zealand.

Dental Decay in Ashburton and New Zealand:

A current question is whether or not Ashburton should re-fluoridate its water supply. I understand that the Canterbury District Health Board (CDHB) has stated that dental decay for Ashburton 6 year-olds has increased by 25% since fluoridation ceased in 2002. The basic data behind this claim does not seem to be publicly available and thus I doubt that it has been independently assessed. My graduate student has searched all modern published literature on this topic and his results clearly show that there is no increase in dental decay rates after the cessation of fluoridation. Any change in the decay rates in this group of children in such a short time is simply statistical ‘noise’.

Statistics for dental decay throughout NZ are publicly available via the NZ Ministry of Health (MoH) website. The latest available statistics for decayed, missing, filled teeth (DMFT) are for 2004. In accordance with the WHO guidelines I focus on decay statistics for 12 year old children as being the relevant indicator.

The MoH statistics reveal that, for the indicator age group, dental decay per child is slightly lower in un-fluoridated Canterbury than for fluoridated Otago and Southland. Dental decay is actually much higher in the fluoridated parts of Canterbury (i.e. Methven and Burnham military camp) but the size of Methven/Burnham’s statistical sample is unreliably small. Dental decay is generally lower in the non-fluoridated areas of the South Island than for the fluoridated areas. However, until those statistics are corrected for socioeconomic status and tested for statistical significance, it is impossible to reach any firm conclusion on the fluoridation effect.

For NZ as a whole any socioeconomic differences would tend to even out. For NZ in total there is a difference in favour of fluoridation equivalent to half a tooth surface (out of a total of 128 tooth surfaces). Not only is this ‘benefit’ clinically irrelevant, it still needs to be corrected for delay in tooth eruption caused by fluoridation. It should also be noted that this supposed benefit is after the children have been exposed to fluoridation for 12 years. That’s an exceedingly expensive way to achieve such a minimal and doubtful benefit.

Misleading Measures of Benefit:

When the fluoridation ‘benefit’ is expressed in the absolute terms of a half tooth surface (out of 128 tooth surfaces) it is obviously insignificant. But the same relationship (of 1.32 to 1.82) can be touted as a 27 percent ‘reduction in decay”. Although mathematically correct, the expression is actually quite misleading and is often used with an intention to mislead. I have noted that NZ health authorities commonly use this percentage method for exaggerated effect. A comment in the Canadian Dental Journal (Vol 67, page 579) is that “Currently the benefits of water fluoridation are exaggerated by the use of misleading measures of effect such as percentage reductions”.

Socioeconomic Differences:

Clearly fluoridation, at least in your South Island, is not effective. I understand that your health officials explain this apparent lack of effectiveness as being caused by socioeconomic differences. That explanation is a contradiction when fluoridation is touted as being a solution for those same socioeconomic differences. Quite obviously fluoridation is not a solution to socioeconomic differences.

Delay in tooth eruption caused by the presence of fluoride:

The presence of fluoride causes a delay in tooth eruption and maturation. This delay is apparent in both deciduous and permanent teeth. It is therefore quite inappropriate for your health officials to use statistics for 5 or 6 year olds to compare dental decay, before and after fluoridation, without allowing for the effect of eruptive delay caused by the presence of fluoride.

Your CDHB uses decay statistics for Ashburton 6 year olds as “evidence” of an increase in dental decay since fluoridation ceased in Ashburton in 2002. But, unless they adjust those statistics to take into account the eruptive delay caused by fluoridation, the comparison is meaningless. Quite apart from that such unchecked observations would contradict current literature on the fluoridation cessation, as mentioned before. A more appropriate comparison might be the decay statistics for Timaru 12 year olds. Timaru ceased fluoridation in 1985 and yet their 12 year olds, who have never experienced the ‘benefit’ of fluoridation, have less decay than for any fluoridated area in the South Island.

I am aware that your CDHB official claims that there is no proof of eruptive delay caused by fluoridation. That claim is incorrect. Upon request I am willing to supply references to a large number of studies that do in fact evidence such a delay.

Adverse Health Effects of Fluoridation:

The subject of fluoridation is not just about teeth. There are numerous peer-reviewed studies detailing a wide range of adverse health effects associated with the long term ingestion of fluoride.

How then can your health officials claim that there is no credible evidence of adverse health effects? I can only suggest that they are in a state of denial. I do have empathy for their position for, after examining the evidence, I too had to swallow my pride and do an about face from what I had been taught, and from what I had also taught. But that is what scientific enquiry is all about.

In the above context I did note that not a single NZ Health official, nor any representative from the Otago School of Dentistry, attended the 2003 International Conference on Fluoridation held in Dunedin, NZ. That was a lost opportunity for them to engage with eminent scientists from throughout the world. Paradoxically I noted that an Ashburton accountant did attend this international conference in order to familiarise with the latest fluoridation issues and to examine the research displays. It is therefore possible that this accountant may be better informed on fluoridation health issues than those who refuse to examine the latest research information.

In my opinion the evidence that fluoridation is more harmful than beneficial  is now overwhelming. My advice is that Ashburton should not re-fluoridate its water supplies.

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