Estimates of fluorosis prevalence in the Cochrane Oral Health Group review (2015)

In 2015 the Cochrane Oral Health Group (COHG) published a systematic review of studies of the dental benefits of water fluoridation.  In addition, the COHG reviewed studies of the prevalence of dental fluorosis in both artificially and naturally fluoridated areas of the world. (1)

The review contained two analyses of dental fluorosis studies – one to calculate prevalence of all levels of fluorosis, and one to calculate the prevalence of fluorosis of potential aesthetic concern.  In both cases the proportion of studies of artificially fluoridated areas was small – 26 out of 90 studies in the first group and only 10 out of 42 studies in the second.

From the data collected in these studies – mainly of naturally fluoridated areas – the COHG review estimates a prevalence of dental fluorosis of aesthetic concern of 8% at 0.1 ppm of fluoride in the water supply, 12% at 0.7 ppm and 15% at 1 ppm.

These figures are much higher than those suggested by the Medical Research Council in its 2002 review, which estimated a 1% prevalence in non-fluoridated areas of the UK and Ireland and a 3% to 4% prevalence in fluoridated areas. (2)

The Cochrane estimates are also much higher than those reported by a 2012 study comparing fluoridated Newcastle upon Tyne and non-fluoridated Manchester, which found a prevalence of 7.1% among Newcastle chidren (less than half the Cochrane figure for areas with 1 ppm of fluoride in their water) and a prevalence of 1.2% among those from Manchester (again, significantly below the Cochrane figure). (3)

The discrepancies may possibly be explained by the fact that the COHG team included many studies of naturally fluoridated areas outside Europe and North America, often in hot climates with very different social conditions and water fluoride concentrations of up to 5 ppm and, in some instances, as high as 7 ppm.

The COHG authors stress that, in its mildest form, fluorosis is visible only to trained examiners under controlled examination conditions.  In addition, they acknowledge that moderate dental fluorosis, where a larger area of the total tooth surface is affected, could be considered to be an ‘unwanted’, rather than adverse, effect.

In their report they say that they have limited confidence in their estimates of the prevalence of fluorosis, both because of variations in the way the studies they reviewed were carried out and because of the quality of those studies.

  1. Iheozor-Ejiofor Z, Worthington HV, Walsh T, O’Malley L, Clarkson JE, Macey R, Alam R, Tugwell P, Welch V, Glenny A-M. Water fluoridation for the prevention of dental caries. Cochrane Database of Systematic Reviews 2015, Issue 6.

  2. Medical Research Council (2002): Working group report: Water fluoridation and health.

  3. McGrady MG, Ellwood RP, Maguire A, Goodwin M, Boothman N (2012): The association between social deprivation and the prevalence and severity of dental caries and fluorosis in populations with and without water fluoridation.  BMC Public Health 12:1122.

COCHRANE REVIEW DESCRIPTION OF MILDEST FORM OF DENTAL FLUOROSIS

“Clinically, the appearance of teeth with fluorosis depends on the severity of the condition.  In its mildest form, there are faint white lines or streaks visible only to trained examiners under controlled examination conditions.”  

COCHRANE REVIEW COMMENT ON MODERATE DENTAL FLUOROSIS AS AN ‘UNWANTED EFFECT’ AND MILD FLUOROSIS NOT EVEN THAT

“It should be acknowledged that moderate fluorosis may be considered an ‘unwanted effect’ rather than an adverse effect. In addition, mild fluorosis may not even be considered an unwanted effect.”

COCHRANE COMMENT ON VARIATIONS IN THE STUDIES REVIEWED

“With regard to dental fluorosis, all studies were observational and we downgraded the quality of the evidence due to an overall high risk of bias and inconsistency due to substantial between-study variation. Our confidence in the effect estimate is limited.”