A team of European researchers have put fluoride to the test – and fluoride (devoid of anecdotal ‘evidence’ from enthusiastic dentists) appears to have flunked. This according to a new study published in the January 2005 issue of the journal Biostatistics (1).

The research team, comprised of scientists from Belgium and Finland, sought to answer the question: “Does fluoride-intake at a young age have a protective effect on caries in permanent teeth?” To answer the question, they utilized data from one of the most detailed studies (“the Signal Tandmobiel study”) of dental health currently available (2). According to the authors, “to our knowledge, the Signal Tandmobiel trial is possibly the largest longitudinal study executed with such great detail on dental aspects.”

For their analysis (a “Bayesian survival analysis”), the authors utilized dental fluorosis as the measure of the children’s fluoride ingestion (3). The authors also took into account something that most dental studies ignore: namely, a possible fluoride-induced delay in tooth eruption (4).

The result?

Whereas in an earlier analysis (5) the authors found a positive effect of fluoride on primary teeth, in this analysis, the authors failed to find a significant effect on 3 of the 4 groupings of permanent teeth which they analyzed. To quote:

“Our analysis shows no convincing effect of fluoride-intake on caries development… This agrees with current guidelines for the use of fluoride in caries prevention, where only the topical application (e.g. fluoride in tooth paste) is considered to be essential.”

The results of this new study are consistent with a recent, widely-publicized study from Australia which found that fluoride ingestion had beneficial effects on the primary, but not the permanent, teeth (6).


(1) Komarek A, Lesaffre E, Harkanen T, Declerck D, Virtanen JI. (2005). A Bayesian analysis of multivariate doubly-interval-censored dental data. Biostatistics 6:145-55

(2) For more information on the Signal Tandmobiel trial, see: http://www.stat.ucl.ac.be/ISpersonnel/lambert/biostat2000/lesaffre.html

(3) The authors’ rationale for using dental fluorosis as the index for fluoride intake was described as follows:

“Unfortunately, fluoride-intake in children cannot be measured accurately. Indeed, fluoride-intake can come from: (1) fluoride supplements (systemic), (2) accidental ingestion of toothpaste or (3) tap water. Further, the intake from these sources can be recorded only crudely. Therefore, it was decided to measure fluoride-intake by the degree of fluorosis on some reference teeth.”

(4) The authors’ rationale for controlling for the date of tooth eruption was described as follows:

“since the emergence of permanent teeth might be delayed by fluoride-intake, evaluating the impact of fluoride-intake should take into account the time at risk for caries. Hence, in our analysis, the response will be the time between emergence and the onset of caries development.”

(5) Vanobbergen J, Martens L, Lesaffre E, Bogaerts K, Declerck D. (2001). Assessing risk indicators for dental caries in the primary dentition. Community Dentistry and Oral Epidemiology 29: 424-34.

(6) Armfield JM, Spencer AJ. (2004). Consumption of nonpublic water: implications for children’s caries experience. Community Dentistry and Oral Epidemiology 32:283-96.