A new paper, published in the September 2005 issue of the Journal of Evidence Based Dental Practice, provides some interesting insight on the relationship between dental fluorosis and tooth decay (1).

The focus of the paper is a study published last year (2), which found that tooth decay increased with the increasing severity of dental fluorosis. As the authors of the current review note:

“Severe fluorosis was associated with a 200% increased odds of having dental caries after controlling for age, gender, socioeconomic status, and area of residence.”

Very mild and mild fluorosis did not, however, appear to increase the risk of cavities. Instead, the increased risk for cavities began to appear when the severity of fluorosis reached a rating of 3 on the Thylstrup-Fejerskov (TF) scale. A rating of 3 on the TF scale is roughly the equivalent of a light case of “moderate” fluorosis on the Dean scale (3).

After discussing these previously published findings, the authors of the review do what others in the dental community have not done: they discuss the potential implications to water fluoridation. To quote:

“The reviewed study contributes useful information in the debate on the role of systemic fluorides, particularly water fluoridation, when the prevalence of dental caries is low, the exposure to topical fluorides is high, and the prevalence of dental fluorosis is increasing worldwide.”

As the authors note, whereas dental fluorosis is caused by ingestion of fluoride, fluoride’s primary benefits come from topical contact, not ingestion. Hence, evidence that excess ingestion of fluoride is not only ineffective, but detrimental to oral health, should be borne in mind when considering water fluoridation and other systemic fluorides. To quote:

“Current evidence suggests that the predominant cariostatic effect of fluoride occurs through daily low-dose exposure easily obtained through fluoridated toothpaste. The findings of this study suggest that dental fluorosis, a marker for systemic fluoride exposure, might be detrimental to oral health. Such evidence, if confirmed in better-controlled and larger studies, should be considered in the debate on the current benefits of water fluoridation in caries prevention.”

In light of this review, it bears mentioning that the CDC’s 1999-2002 national survey of dental fluorosis in the US, found that 3 to 4% of children and adolescents now have moderate or severe dental fluorosis (4). Thus, upwards of 1 in 25 American children may be at increased risk of developing cavities as a direct result of their fluoride exposure.

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For further information on the relationship between fluorosis and tooth decay, see: http://www.fluoridealert.org/studies/dental_fluorosis04/

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References:

(1) Cunha-Cruz J, Nadanovsky P. (2005). Dental fluorosis increases caries risk. Journal of Evidence Based Dental Practice 5: 170-171.

(2) Wondwossen F, et al. (2004). The relationship between dental caries and dental fluorosis in areas with moderate- and high-fluoride drinking water in Ethiopia. Community Dentistry and Oral Epidemiology 32: 337-44.

(3) Comparison of Dean Index with TF index based on: Fejerskov O, Richards A, DenBesten P. (1996). The Effect of Fluoride on Tooth Mineralization. In: Fejerskov O, Ekstrand J, Burt B, Eds. Fluoride in Dentistry. Munksgaard, Denmark. pp. 112-146.

(4) See Table 23 at: http://www.cdc.gov/mmwr/preview/mmwrhtml/ss5403a1.htm. See also CDC’s press release at: http://www.cdc.gov/od/oc/media/pressrel/r050825.htm