Why is this question important?
Tooth decay (also called a cavity or caries) is when a small hole develops in a tooth. This happens because bacteria (tiny living organisms) that live in the mouth feed on sugar in the food we eat. As they feed, the bacteria produce acid that attacks teeth. If teeth are not cleaned regularly after eating, or if someone consumes a lot of sugary foods and drinks, the repeated acid attacks can create holes in the hard outer surface of the teeth (enamel). If untreated, these holes can deepen and damage the layer of tooth underneath the surface (dentine).
Many people around the world develop tooth decay at some point in their life. In most adolescents and children over the age of six years, decay damages the biting surfaces of the permanent teeth at the back of the mouth.
To prevent decay, dentists can apply a dental sealant, or a fluoride varnish, directly onto the back teeth. A dental sealant is a coating made from an adhesive material such as resin or glass ionomer, which the dentists applies once to teeth. It seals off the grooves in teeth that tend to collect food, and protects them from the acid. By comparison, a fluoride varnish is a sticky paste that contains high levels of fluoride; fluoride is a mineral naturally present in teeth that protects them from damage. Fluoride varnishes need to be applied to teeth by the dentist two to four times a year.
We reviewed the evidence from research studies to find out whether sealants or fluoride varnishes, or a combination, are better for preventing decay in the permanent back teeth of children and adolescents.
How did we identify and evaluate the evidence?
We searched the medical literature for randomised controlled studies (clinical studies where people are randomly put into one of two or more treatment groups), because these studies provide the most robust evidence about the effects of a treatment. We then compared the results, and summarised the evidence from all the studies. We assessed how certain the evidence was. To do this, we considered factors such as the way studies were conducted, study sizes and consistency of findings across studies. Based on our assessments, we categorised the evidence as being of very low, low, moderate or high certainty.
What did we find?
We found 11 studies that included 3374 children aged between five and 10 years at the start of the studies. Children were randomly assigned to treatment with either sealant or fluoride varnish, or both. They were followed for between one and nine years. Studies compared the number of children who had tooth decay in the dentine of their back teeth in different treatment groups.
The evidence was of very low certainty so we are not able to be confident in the findings.
When we combined four studies that compared resin sealants versus fluoride varnish, we found that neither intervention worked better than the other.
The three individual studies that compared sealants made from glass ionomer versus fluoride varnish could not be combined and had mixed results.
One small study found that using both sealants and fluoride varnish may work better than using fluoride varnish alone.
Five studies reported that no side effects were associated with the use of either sealants or fluoride varnishes. The other studies did not mention whether or not any side effects occurred.
What do these results mean?
At present, we do not know whether it is better to apply sealants or fluoride varnish to prevent tooth decay in children's back teeth. We do know that both interventions are effective for reducing tooth decay, and current evidence does not suggest that one works better than the other.
Fourteen studies are currently underway. Their findings could improve the evidence in future versions of this review.
How-up-to date is this review?
The evidence is current to March 2020.
Applying fluoride varnish or resin-based fissure sealants to first permanent molars helps prevent occlusal caries, but it has not been possible in this review to reach reliable conclusions about which one is better to apply. The available studies do not suggest either intervention is superior, but we assessed this evidence as having very low certainty. We found very low-certainty evidence that placing resin-based sealant as well as applying fluoride varnish works better than applying fluoride varnish alone. Fourteen studies are currently ongoing and their findings may allow us to draw firmer conclusions about whether sealants and varnish work equally well or whether one is better than the other.
Most of the detected increment in dental caries among children above the age of six years and adolescents is confined to occlusal surfaces of posterior permanent molars. Dental sealants and fluoride varnishes are much used to prevent caries. As the effectiveness of both interventions in controlling caries as compared with no intervention has been demonstrated previously, this review aimed to evaluate their relative effectiveness. It updates a review published originally in 2006 and updated in 2010 and in 2016.
Our primary objective was to evaluate the relative effectiveness of dental sealants (i.e. fissure sealant) compared with fluoride varnishes, or fissure sealants plus fluoride varnishes compared with fluoride varnishes alone, for preventing dental caries in the occlusal surfaces of permanent teeth of children and adolescents.
Our secondary objectives were to evaluate whether effectiveness is influenced by sealant material type and length of follow-up, document and report on data concerning adverse events associated with sealants and fluoride varnishes, and report the cost effectiveness of dental sealants versus fluoride varnish in caries prevention.
Cochrane Oral Health's Information Specialist searched the following databases: Cochrane Oral Health's Trials Register (to 19 March 2020), the Cochrane Central Register of Controlled Trials (CENTRAL) (the Cochrane Library, 2020, Issue 2), MEDLINE Ovid (1946 to 19 March 2020) and Embase Ovid (1980 to 19 March 2020). We searched the US National Institutes of Health Trials Registry (ClinicalTrials.gov) and the World Health Organization International Clinical Trials Registry Platform for ongoing trials. There were no restrictions on the language or date of publication.
We included randomised controlled trials with at least 12 months of follow-up comparing fissure sealants, or fissure sealants plus fluoride varnishes, versus fluoride varnishes, for preventing caries in the occlusal surfaces of permanent posterior teeth (i.e. premolar or molar teeth), in participants younger than 20 years of age at the start of the study.
At least two review authors independently screened search results, extracted data from included studies and assessed their risk of bias. We attempted to contact study authors to obtain missing or unclear information. We grouped and analysed studies on the basis of sealant material type: resin-based sealant or glass ionomer-based sealant (glass ionomer and resin-modified glass ionomer sealant), and different follow-up periods. We calculated the odds ratio (OR) for risk of caries on occlusal surfaces of permanent molar teeth. For trials with a split-mouth design, we used the Becker-Balagtas OR. One cluster-randomised trial provided precise estimates in terms of risk ratio (RR), which we used. For continuous outcomes and data, we used means and standard deviations to obtain mean differences (MD). For meta-analysis, we used the random-effects model when we combined data from four or more studies. We presented all measures with 95% confidence intervals (CIs). We assessed the certainty of the evidence using GRADE criteria.
We included 11 trials with 3374 participants aged five to 10 years when trials started. Three trials are new since the 2016 update. Two trials did not contribute data to our analysis.
Sealant versus fluoride varnish
Resin-based fissure sealants versus fluoride varnishes
Seven trials evaluated this comparison (five contributing data). We are uncertain if resin-based sealants may be better than fluoride varnish, or vice versa, for preventing caries in first permanent molars at two to three years' follow-up (OR 0.67, 95% CI 0.37 to 1.19; I2 = 84%; 4 studies, 1683 children evaluated). One study measuring decayed, missing and filled permanent surfaces (DMFS) and decayed, missing and filled permanent teeth (DMFT) increment at two years suggested a small benefit for fissure sealant (DMFS MD –0.09, 95% CI –0.15 to –0.03; DMFT MD –0.08, 95% CI –0.14 to –0.02; 542 participants), though this may not be clinically significant. One small study, at high risk of bias, reported a benefit for sealant after four years in preventing caries (RR 0.42, 95% CI 0.21 to 0.84; 75 children) and at nine years (RR 0.48, 95% CI 0.29 to 0.79; 75 children). We assessed each of these results as having very low certainty.
Glass ionomer-based sealants versus fluoride varnishes
Three trials evaluated this comparison: one trial with chemically cured glass ionomer and two with resin-modified glass ionomer. Studies were clinically diverse, so we did not conduct a meta-analysis. In general, the studies found no benefit of one intervention over another at one, two and three years, although one study, which also included oral health education, suggested a benefit from sealants over varnish for children at high risk of caries. We assessed this evidence as very low certainty.
Sealant plus fluoride varnish versus fluoride varnish alone
One split-mouth trial analysing 92 children at two-year follow-up found in favour of resin-based fissure sealant plus fluoride varnish over fluoride varnish only (OR 0.30, 95% CI 0.17 to 0.55), which represented a clinically meaningful effect of a 77% reduction in caries after two years; however, we assessed this evidence as very low certainty.
Five trials (1801 participants) (four using resin-based sealant material and one using resin-modified glass ionomer) reported that no adverse events resulted from use of sealants or fluoride varnishes over one to nine years. The other studies did not mention adverse events.