Is the use of topical fluoride during early childhood associated with mottling of teeth?
Key messages
There is some evidence that higher levels of fluoride (1000 parts per million (ppm) or more) in toothpaste given to children from 1 to 2 years of age are associated with an increased risk of dental fluorosis (mottling/discolouration) in permanent teeth.
There is inconclusive evidence on the risk of having dental fluorosis in permanent teeth with regard to when children should start toothbrushing, the amount of toothpaste used, and the frequency of toothbrushing.
What is dental fluorosis (mottling)?
Previous research has indicated that the use of toothpaste containing fluoride can prevent tooth decay. However, young children exposed to too much fluoride while their teeth are developing may end up with dental fluorosis in the permanent teeth. Fluorosis can be seen as white stripes, streaks, larger opaque patches, brownish discolouration, pitting, or rupture on permanent teeth.
What did we want to find out?
In this updated review, we wanted to know if more well-designed studies have been published recently to determine if the use of topical fluoride during early childhood is associated with the mottling of permanent teeth.
What did we do?
We searched for studies that explored the association between various topical fluoride exposures in young children (such as the age at which they started toothbrushing, frequency of brushing, and concentration of fluoride toothpaste used) and their risk of having fluorosis in their permanent teeth. We compared and summarized the results of the studies and rated our confidence in the evidence, based on factors such as study methods and sizes.
What did we find?
We found a total of 43 studies published between 1988 and 2022, involving 32,181 children. The age range of the children at the time of the assessment of fluorosis was 6 to 18 years. The studies varied in how they were conducted: 3 were experimental studies and 40 were observational studies. The studies were conducted in Australia, Belgium, Brazil, Canada, Colombia, Germany, India, Ireland, Mexico, Norway, Poland, Sweden, Thailand, the UK, and the USA.
Main results
The fluorosis identified in most of the studies was considered to be mild fluorosis.
We could not tell if the risk of having fluorosis in the permanent teeth is associated with when a child starts receiving topical fluoride varnish applications and toothbrushing with fluoride toothpaste, the amount of toothpaste used by the child, or the frequency of toothbrushing.
Toothbrushing with toothpaste with a fluoride concentration of 1000 ppm or more from 1 to 2 years of age is likely to be associated with an increased chance of developing dental fluorosis in permanent teeth.
What are the limitations of the evidence?
Often, we had little confidence in the evidence due to the methods used within the included studies.
Sometimes the studies' reporting of the type of fluoride, the frequency of toothbrushing, and the amount of toothpaste used was poor, and we were unable to determine if the exposure to fluoride occurred before the children were 6 years old. We did not include these studies in the analysis, so some evidence may have been missed out.
How up to date is this evidence?
This review updates our previous review. The evidence is current to July 2022.
Most evidence identified mild fluorosis as a potential adverse outcome of using topical fluoride at an early age. There is low- to very low-certainty and inconclusive evidence on the risk of having fluorosis in permanent teeth for: when a child starts receiving topical fluoride varnish application; toothbrushing with fluoride toothpaste; the amount of toothpaste used by the child; and the frequency of toothbrushing. Moderate-certainty evidence from RCTs showed that children who brushed with 1000 ppm or more fluoride toothpaste from one to two years of age until five to six years of age probably had an increased chance of developing dental fluorosis in permanent teeth.
It is unethical to propose new RCTs to assess the development of dental fluorosis. However, future RCTs focusing on dental caries prevention could record children's exposure to topical fluoride sources in early life and evaluate the dental fluorosis in their permanent teeth as a long-term outcome. In the absence of these studies and methods, further research in this area will come from observational studies. Attention needs to be given to the choice of study design, bearing in mind that prospective controlled studies will be less susceptible to bias than retrospective and uncontrolled studies.
This is an update of a review first published in 2010. Use of topical fluoride has become more common over time. Excessive fluoride consumption from topical fluorides in young children could potentially lead to dental fluorosis in permanent teeth.
To describe the relationship between the use of topical fluorides in young children and the risk of developing dental fluorosis in permanent teeth.
We carried out electronic searches of the Cochrane Oral Health Trials Register, CENTRAL, MEDLINE, Embase, three other databases, and two trials registers. We searched the reference lists of relevant articles. The latest search date was 28 July 2022.
We included randomized controlled trials (RCTs), quasi-RCTs, cohort studies, case-control studies, and cross-sectional surveys comparing fluoride toothpaste, mouth rinses, gels, foams, paint-on solutions, and varnishes to a different fluoride therapy, placebo, or no intervention. Upon the introduction of topical fluorides, the target population was children under six years of age.
We used standard methodological procedures expected by Cochrane and used GRADE to assess the certainty of the evidence. The primary outcome measure was the percentage prevalence of fluorosis in the permanent teeth. Two authors extracted data from all included studies. In cases where both adjusted and unadjusted risk ratios or odds ratios were reported, we used the adjusted value in the meta-analysis.
We included 43 studies: three RCTs, four cohort studies, 10 case-control studies, and 26 cross-sectional surveys. We judged all three RCTs, one cohort study, one case-control study, and six cross-sectional studies to have some concerns for risk of bias. We judged all other observational studies to be at high risk of bias. We grouped the studies into five comparisons.
Comparison 1. Age at which children started toothbrushing with fluoride toothpaste
Two cohort studies (260 children) provided very uncertain evidence regarding the association between children starting to use fluoride toothpaste for brushing at or before 12 months versus after 12 months and the development of fluorosis (risk ratio (RR) 0.98, 95% confidence interval (CI) 0.81 to 1.18; very low-certainty evidence).
Similarly, evidence from one cohort study (3939 children) and two cross-sectional studies (1484 children) provided very uncertain evidence regarding the association between children starting to use fluoride toothpaste for brushing before or after the age of 24 months (RR 0.83, 95% CI 0.61 to 1.13; very low-certainty evidence) or before or after four years (odds ratio (OR) 1.60, 95% CI 0.77 to 3.35; very low-certainty evidence), respectively.
Comparison 2. Frequency of toothbrushing with fluoride toothpaste
Two case-control studies (258 children) provided very uncertain evidence regarding the association between children brushing less than twice per day versus twice or more per day and the development of fluorosis (OR 1.63, 95% CI 0.81 to 3.28; very low-certainty evidence).
Two cross-sectional surveys (1693 children) demonstrated that brushing less than once per day versus once or more per day may be associated with a decrease in the development of fluorosis in children (OR 0.62, 95% CI 0.53 to 0.74; low-certainty evidence).
Comparison 3. Amount of fluoride toothpaste used for toothbrushing
Two case-control studies (258 children) provided very uncertain evidence regarding the association between children using less than half a brush of toothpaste, versus half or more of the brush, and the development of fluorosis (OR 0.77, 95% CI 0.41 to 1.46; very low-certainty evidence). The evidence from cross-sectional surveys was also very uncertain (OR 0.92, 95% CI 0.66 to 1.28; 3 studies, 2037 children; very low-certainty evidence).
Comparison 4. Fluoride concentration in toothpaste
There was evidence from two RCTs (1968 children) that lower fluoride concentration in the toothpaste used by children under six years of age likely reduces the risk of developing fluorosis: 550 parts per million (ppm) fluoride versus 1000 ppm (RR 0.75, 95% CI 0.57 to 0.99; moderate-certainty evidence); 440 ppm fluoride versus 1450 ppm (RR 0.72, 95% CI 0.58 to 0.89; moderate-certainty evidence). The age at which the toothbrushing commenced was 24 months and 12 months, respectively. Two case-control studies (258 children) provided very uncertain evidence regarding the association between fluoride concentrations under 1000 ppm, versus concentrations of 1000 ppm or above, and the development of fluorosis (OR 0.89, 95% CI 0.52 to 1.52; very low-certainty evidence).
Comparison 5. Age at which topical fluoride varnish was applied
There was evidence from one RCT (123 children) that there may be little to no difference between a fluoride varnish application before four years, versus no application, and the development of fluorosis (RR 0.77, 95% CI 0.45 to 1.31; low-certainty evidence). There was low-certainty evidence from two cross-sectional surveys (982 children) that the application of topical fluoride varnish before four years of age may be associated with the development of fluorosis in children (OR 2.18, 95% CI 1.46 to 3.25).