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Definitions of terms

This page explains the more common terms and acronyms used in fluoridation discussion.

TermMeaning and commentary
Fluoride, fluorides This is a generic term for a range of compounds containing the fluoride ion. Scientifically it is inaccurate, as “fluoride” does not exist in isolation.
The fluoride compounds used in water fluoridation are:
  • Hydrofluorosilicic acid (often abbreviated to "HFA"
    Chemical formula: H2SiF6
    Classification: Schedule 7 (dangerous poison)
    Hazchem Class 6 (acutely toxic ) & 8 (corrosive)
  • Sodium hexafluorosilicate (often called Sodium silicofluorides)
    Chemical formula: Na2SiF6
    Classification; schedule 6 (poison)
    Hazchem Class 6 (acutely toxic) & 9 (ecotoxic to vertebrates)
  • Sodium Fluoride. This is rarely used today in water fluoridation, but is commonly used in fluoride tablets.
    Chemical formula: NaF
    Classification: T (toxic)
    Hazchem Class 6 (acutely toxic) & 9 (ecotoxic to vertebrates)
  • (Calcium fluoride). This is not used in artificial fluoridation. It is the type of fluoride naturally in water, at varying levels.
    Chemical formula: CaF2
    It is considered non-toxic, having a similar toxicity to common table salt.
FluoridationThe addition of fluoride compounds to the public water supply
GradeThe purity of a chemical. There are 3 grades relevant to the fluoridation issue:
  1. Pharmaceutical Grade: very high purity, used in medication. It is used in fluoride tablets, fluoride toothpaste, and was used for early experiments with fluoride.
  2. Food Grade: lower than pharmaceutical grade, but free of impurities that would make it potentially dangerous to consume regularly. At this time, there is no such thing as Food Grade fluoride, as it is illegal to add fluoride to food.
  3. Water Treatment Grade: a grade specified only for use in water treatment, allowing significant levels of toxic contaminants. In NZ it is specified by a private organisation, not the Government. No testing appears to be done to ensure compliance with this standard.
Research terms
Original researchScientific research, sometimes called a study. To be accepted as part of the fluoridation debate, the Ministry of Health specifies that it must be published in an internationally recognised peer-reviewed journal. Neither the Ministry nor DHBs adhere to this standard. It is important to know how objective the researcher(s) are, and, particularly, whether the research was funded by an organisation with a political position on fluoridation. Note: only original research can prove or disprove a claim about fluoridation.
Peer reviewThis is a standard method of assessing scientific research. The research data is provided to scientists with expertise in the subject. Those scientists assess the methods used and the validity of conclusions drawn. Journals have peer review panels that assess research articles submitted for publication. The system is not perfect. Once a powerful group in the scientific community adopts a theory, it often rejects opposing research on a biased basis. This is a serious shortfall with medical and dental journals regarding fluoride research. Those peer reviewers are typically pro-fluoridation. Consequently, much research on adverse health effects of fluoride appears in other more specialist journals because the main medical and dental journals misuse the peer review process to deny publication.
ReviewA review of, and report on, original research, but may include non-research material. Typically reviews are conducted on behalf of a decision-maker, such as a Government or government agency. Examples are the National Research Council review, 2006, commissioned by the US Environmental Protection Association. It is important to know how objective the reviewer, or members of a review board, are when assessing the reliability of a review. Note: a review CANNOT prove or disprove a claim about fluoridation.
Confounding factor

Factors other than water fluoridation that can influence the level of tooth decay. Unless these confounding factors are determined accurately it is not possible to say that a difference in tooth decay rates is, or is not, due to water fluoridation.

A list of typical confounding factors is provided by the 1999 Review for the Australian National Health and Medical Research Council "Review of Water Fluoridation and Fluoride Intake from Discretionary Fluoride Supplements":

  1. Most studies have been ‘ecological’ in nature, in that they have compared populations with differing exposure to fluoride in drinking water rather than individuals with differing exposure. Ecological studies do not guarantee similar associations as studies of individuals and generally provide weak evidence for reasons described in various epidemiology texts (Rothman & Greenland, 1998).
  2. Amongst fluoridated areas are some with high and some with low caries rates. A similar spectrum exists amongst non-fluoridated areas. Under these circumstances the validity of ecological comparisons can be distorted by manipulation of the areas compared.
  3. Many studies of populations exposed to differing levels of fluoride in potable water report target fluoride levels rather that actual levels. It has been demonstrated that water fluoride levels achieved may differ considerably from the target.
  4. Fluoridated and non-fluoridated areas often differ in other aspects important to dental health. For example they may differ in respect to socio-economic status, the degree of access to dental services, dental procedures and the typical diet. These differences must be taken into account when comparing caries rates.
  5. Several important sources of fluoride exposures are available besides fluoridated water and differences in their use between fluoridated and nonfluoridated areas must also be considered when comparing caries rates. These include toothpastes containing various concentrations of fluoride and use of fluoride supplements. Use of bottled water may also influence fluoride exposure.
  6. A ‘diffusion’ effect from fluoridated beverages and foods prepared in fluoridated areas may contribute to the fluoride intake of individuals in the non-fluoridated areas that they are distributed.
  7. A ‘dilution’ effect from non-fluoridated beverages and foods prepared in nonfluoridated areas and the use of reverse osmosis water filters that remove fluoride either in the home or by some beverage manufacturers may contribute to a decreased fluoride exposure in fluoridated communities.
  8. Some evidence exists that tooth eruption is delayed in fluoridated areas. It has been suggested that a proper comparison of caries rates should involve children one year older in fluoridated areas than in non-fluoridated areas.

Teeth and decay
HydroxyapatiteThe chemical structure of tooth enamel (and bone)
FluorapatiteWhen the fluoride ion is incorporated into hydroxyapatite it becomes fluorapatite.
RemineralisationThe re-incorporation of minerals back into partially demineralised tooth enamel. This happens naturally. Fluoride may assist in this process, but a view also exists that too much fluoride might block re-absorption of other minerals
FluorosisDamage to the teeth or bone structure caused by excessive fluoride exposure. In relation to teeth, it is caused only during tooth formation – in the first six years of life. It is graded according to the "Dean index" formulated by H Trendley Dean in his initial studies during the 1930s. The grades are:
Criteria for Dean's Fluorosis Index
Score Criteria
Normal The enamel represents the usual translucent semivitriform type of structure. The surface is smooth, glossy, and usually of a pale creamy white colour.
Questionable The enamel discloses slight aberrations from the translucency of normal enamel, ranging from a few white flecks to occasional white spots. This classification is utilized in those instances where a definite diagnosis of the mildest form of fluorosis is not warranted and a classification of "normal" is not justified.
Very Mild Small opaque, paper white areas scattered irregularly over the tooth but not involving as much as 25% of the tooth surface. Frequently included in this classification are teeth showing no more than about 1-2 mm of white opacity at the tip of the summit of the cusps of the bicuspids or second molars.
Mild The white opaque areas in the enamel of the teeth are more extensive but do not involve as much as 50% of the tooth.
Moderate All enamel surfaces of the teeth are affected, and the surfaces subject to attrition show wear. Brown stain is frequently a disfiguring feature.
Severe Includes teeth formerly classified as "moderately severe and severe." All enamel surfaces are affected and hypoplasia is so marked that the general form of the tooth may be affected. The major diagnostic sign of this classification is discrete or confluent pitting. Brown stains are widespread and teeth often present a corroded-like appearance.
Source: Dean, 1942. As Reproduced in "Health Effects of Ingested Fluoride" National Academy of Sciences, 1993. pp. 169.
Lesion, carious lesionThe formation of cavities in the teeth by the action of bacteria; tooth decay
SystemicBeing taken into the body and blood stream. Early fluoride researchers believed fluoride had to be taken systemically (i.e. swallowed) and incorporated into tooth enamel while it was forming. This is now known to be incorrect. This was the basis for fluoridation.
TopicalSurface application or effect. For example brushing with fluoride toothpaste, or applying sun block to your skin
Measures used in dental research
Tooth surfaceTeeth have either 4 surfaces (front 6 teeth of the upper and lower jaw) or 5 surfaces (grinding teeth (molars)). Statistics on surfaces affected by tooth decay give a more sensitive measure than statistics on whole teeth. There are 128 tooth surfaces in an adult with all their teeth, not counting the wisdom teeth.
For example a tooth with a filling on one surface only and a tooth fillings on 3 surfaces would both count as count as 1 dmft/DMFT. But they would counts as 1 dmfs/DMFS and 3 dmfs/DMFS respectively.
dmfs Decayed (d), missing(m), or filled (f) surfaces of the first teeth.
DMFS Decayed (d), missing(m), or filled (f) surfaces of the permanent (adult) teeth
dmft Decayed (d), missing(m), or filled (f) first teeth.
DMFT Decayed (d), missing(m), or filled (f) permanent (adult) teeth
Percent caries-freeThe percentage of people with NO tooth decay (i.e. zero dmfs, DMFS, dmft, or DMFT). It is a cruder measure than the other measures, as a person with 1 filling counts the same as a person with 10 missing teeth.
CariesTooth decay. It includes decay that has yet to be filled, filled cavities, and teeth missing due to decay.
Deciduous teeth First teeth, baby teeth, or milk teeth. These begin falling out at around age 4 or 5, and are replaced by the permanent teeth. The process is complete at some point during the teenage years.
EruptionThe tooth breaking through the gum and into the mouth. For children, this is “teething”. The teeth are formed in the jaw, below the gums. Eventually they break through the gum and into the mouth. The first 3 years after eruption is the period when teeth are most susceptible to decay.
Delayed eruptionThere is some evidence that fluoridation causes teeth to erupt about a year later than they would without fluoridation. This is called delayed eruption. If proven, it would invalidate every study based on children of the same age. The most reliable study to date is Komarek, 2005. This study confirmed the delay, and that teeth examined the same time after eruption showed no difference in tooth decay between fluoridated and unfluoridated children. At this point, delayed eruption is not conclusively proven, but the evidence is substantial.
Exposure measures
Dosethe total amount of a fluoride consumed in a day from all sources. This is different from concentration. For example, if water has a concentration of 1ppm fluoride (1 mg/litre) a person drinking 1 litre will get a 1 mg dose of fluoride. A person drinking two litres will get a 2 mg dose of fluoride. Promoters of fluoridation often confuse dose and concentration, claiming a concentration of 1ppm (for example is safe). Such a statement is scientific nonsense. Only dose is relevant to determining levels related to health risks.
Reference Daily Intake (RDI) This is the minimum level of a nutrient required, below which medical symptoms appear. Examples are iodine, calcium, and iron. There is no bodily requirement for fluoride, hence there is no RDI for fluoride. This is because fluoride is not a nutrient.
Adequate intake (AI)This does not mean what it seems. It means that there is no scientifically determined need for the substance at all, but people generally consume the stated amount with no apparent side effects. Since fluoridating countries do not monitor side effects of fluoride, it is impossible to state an adequate dose of fluoride. However, New Zealand and Australia cite 3 mg/day as an AI. This used to be cited as the maximum safe intake (Upper Limit, UL)
LOAELLowest Observed Adverse Effect Level
The lowest daily dose at which adverse effects are observed. Typically in toxicology, a safe level is considered to be one tenth of the LOEAL, to allow for variations within a whole population
NOAELNo Observed Adverse Effect Level.The highest dose at which no adverse effects are observed.
Margin of safety (factor)In toxicology it is usual to use the LOAEL from a study and apply a safety factor to protect all members of society. This is because people have differing sensitivities to toxins (like fluoride). The iusual sasfty factor is 10. For fluoridation there is no margin of sasfety applied. The claim by promoters is that this is because the only harm is dental fluorosis (which is incorrect) and dnetal fluorosis is only cosmetic (which is incorrect)
Upper Limit (UL)The safe upper limit of daily intake. No UL has ever been scientifically determined for infants, but NZFSA quotes the UL as 0.7 mg/day. It is calculated on the claimed safe intake of .05 mg/kg bwt/day for adults, adjusted for body weight. The UL for adults is 10 mg/day. This has apparently been set for political reasons, as it is within the range identified as potentially causing skeletal fluorosis in the long term (Hodge). The authors cite out of date studies from the 1950’s as showing no skeletal fluorosis at this intake (in contradiction to Hodge). Harm has been demonstrated below this level (NRC 2006). Moreover, no margin of safety was allowed. The excuse was that the only harm was dental fluorosis, that this is only cosmetic (which is false) and therefore no safety margin was necessary.