Abstract: We included 38 trials that involved a total of 7924 children; seven trials were new for this update (1693 participants). Fifteen trials evaluated the effects of resin-based sealant versus no sealant (3620 participants in 14 studies plus 575 tooth pairs in one study); three trials with evaluated glass ionomer sealant versus no sealant (905 participants); and 24 trials evaluated one type of sealant versus another (4146 participants). Children were aged from 5 to 16 years. Trials rarely reported background exposure to fluoride of trial participants or baseline caries prevalence. Resin-based sealant versus no sealant: second-, third- and fourth-generation resin-based sealants prevented caries in first permanent molars in children aged 5 to 10 years (at 24 months follow-up: OR 0.12, 95% CI 0.08 to 0.19, 7 trials (5 published in the 1970s; 2 in the 2010s), 1548 children randomised, 1322 children evaluated; moderate-quality evidence). If we were to assume that 16% of the control tooth surfaces were decayed during 24 months of follow-up (160 carious teeth per 1000), then applying a resin-based sealant would reduce the proportion of carious surfaces to 5.2% (95% CI 3.13% to 7.37%). Similarly, assuming that 40% of control tooth surfaces were decayed (400 carious teeth per 1000), then applying a resin-based sealant would reduce the proportion of carious surfaces to 6.25% (95% CI 3.84% to 9.63%). If 70% of control tooth surfaces were decayed, there would be 19% decayed surfaces in the sealant group (95% CI 12.3% to 27.2%). This caries-preventive effect was maintained at longer follow-up but evidence quality and quantity was reduced (e.g. at 48 to 54 months of follow-up: OR 0.21, 95% CI 0.16 to 0.28, 4 trials, 482 children evaluated; RR 0.24, 95% CI 0.12 to 0.45, 203 children evaluated). Although studies were generally well conducted, we assessed blinding of outcome assessment for caries at high risk of bias for all trials (blinding of outcome assessment is not possible in sealant studies because outcome assessors can see and identify sealant). Glass ionomer sealant versus no sealant: was evaluated by three studies. Results at 24 months were inconclusive (very low-quality evidence). One sealant versus another sealant: the relative effectiveness of different types of sealants is unknown (very low-quality evidence). We included 24 trials that directly compared two different sealant materials. Comparisons varied in terms of types of sealant assessed, outcome measures chosen and duration of follow-up. Adverse events: only four trials assessed adverse events. No adverse events were reported. Resin-based sealants applied on occlusal surfaces of permanent molars are effective for preventing caries in children and adolescents. Our review found moderate-quality evidence that resin-based sealants reduced caries by between 11% and 51% compared to no sealant, when measured at 24 months. Similar benefit was seen at timepoints up to 48 months; after longer follow-up, the quantity and quality of evidence was reduced. There was insufficient evidence to judge the effectiveness of glass ionomer sealant or the relative effectiveness of different types of sealants. Information on adverse effects was limited but none occurred where this was reported. Further research with long follow-up is needed.

Plain-language summary: We included 38 studies that involved 7924 young people (aged 5 to 16 years) among whom a variety of dental sealants was used to prevent tooth decay. Young people in the studies represented the general population. The review includes studies available from a search of the literature up to 3 August 2016. We assessed all studies as being at high risk of bias because the dental professionals who are measuring the outcomes can see whether or not sealant has been used. Fifteen studies compared resin-based sealants to no sealants and found that children who had sealant applied to their back teeth were less likely to have tooth decay in their back teeth than children with no sealant. We were able to combine data from seven of these studies (including two published since 2010), which involved children who were aged from 5 to 10 years when the sealants were applied. This showed that if 40% of back teeth develop decay over 24 months, using sealant reduces this to 6%. Similar benefits for resin-based sealants were shown up to four years. The effect appeared to persist when measured up to nine years, but there was less evidence. Results were inconclusive when glass ionomer-based sealant was compared with no sealant and when one type of sealant material was compared with another. Four studies assessed possible problems from using sealants; none were reported. We found moderate-quality evidence that resin-based sealant is more effective than no sealant for preventing tooth decay, reducing it by between 11% and 51% more than in children without sealant (measured two years after application). 'Moderate quality' means we are reasonably certain of this finding, although it is possible that future research could change it. Most of the studies included in this analysis were carried out in the 1970s. We are not able to draw conclusions about the other comparisons included in our review as the available evidence is very low quality. More studies with long follow-up times are needed.