Topical Fluoride as a Cause of Dental Fluorosis in Children

Is the use of topical fluoride during early childhood linked to the development of fluorosis in permanent teeth?

Children aged 1 to 2 years who begin using toothpaste with higher fluoride concentrations (1,000 ppm or more vs less than 1,000 ppm) are at increased risk of developing dental fluorosis (mottling or discoloration) in permanent teeth.¹ (Strength of Recommendation: B, inconsistent or limited-quality patient-oriented evidence.)

Fluoride in toothpaste and varnish is known to reduce the risk of tooth decay. Although not defined in this review, several health risk assessments and longitudinal studies indicate that a fluoride intake threshold of approximately 0.06 mg/kg body weight per day is associated with increased risk of dental fluorosis. The US Environmental Protection Agency's reference dose for fluoride is 0.06 mg/kg per day to protect against adverse effects in children, and observational studies have shown fluorosis prevalence rises significantly above this intake level.^2–4 In more severe cases of dental fluorosis, the enamel may become pitted and mottled with dark yellow or brown stains.⁵ The prevalence of dental fluorosis is approximately 11.3% in children aged 8 to 13 years.⁶ This Cochrane review examined the potential connection between early childhood use of topical fluoride and the development of dental fluorosis.

This review included three randomized controlled trials, four cohort studies, 10 case-control studies, and 26 cross-sectional surveys published from 1988 to 2022 and involving 32,181 children aged 6 to 18 years.¹ Most of the studies were conducted in the United States with some performed in the United Kingdom, Canada, and Brazil. These studies explored various factors (eg, when children started brushing their teeth, how often they brushed, the fluoride concentration in the toothpaste used) that related to the risk of developing fluorosis. The prevalence of fluorosis was measured by its presence in permanent teeth between ages 6 and 18 years.

Most of the studies were observational.¹ Reporting of the amount of fluoride exposure was inconsistent among these studies, making findings less reliable and generalizable. In addition, assessment of the outcomes was not consistent among studies.

The included studies primarily reported an association between topical fluoride use in children younger than 6 years and an increased risk of dental fluorosis in permanent teeth, particularly when exposure exceeded recommended levels.¹ However, the strength of this evidence is limited. According to the GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) approach, the overall quality of evidence was rated as low to very low.

The review authors found very uncertain evidence on the association between the age at which fluoride toothpaste was introduced to children and the risk of developing dental fluorosis.¹ Comparisons of initiating toothbrushing before or after age 12 months, before or after age 24 months, and before or after age 4 years showed no consistent or reliable association with fluorosis risk. Similarly, evidence on the frequency of toothbrushing (less than twice daily vs twice or more daily) and the amount of toothpaste used (less than half a brush vs half a brush or more) was also very uncertain and inconclusive. For fluoride varnish, one small randomized controlled trial found little to no difference in fluorosis development when varnish was applied before age 4 years. However, low-certainty evidence from observational studies suggested a potential increase in risk. Overall, these findings reflect a low level of certainty and highlight the need for more rigorous research in this area.