Liu 2012.

Methods	Trial design: parallel‐group study, 4 randomly assigned treatment arms (sealant, fluoride varnish, silver diamine fluoride solution, and placebo) Year the study started: 2008 Follow‐up: 24 months
Participants	Location: China, children were chosen from primary schools Inclusion criteria: children had to have at least 1 sound permanent first molar with deep fissures or fissures with signs of early (enamel) caries viewed as wet, with opacities and discolouration (proportion of early caries 35% of tooth sites). Clinical examinations included DIAGNOdent readings and were done by a dentist. Age at baseline: mean age 9.1 years (range 8 to 10 years) Gender: 248 boys and 253 girls Baseline caries: baseline mean dmft scores with SD for groups: sealant 3.19 (2.68); placebo 3.55 (2.54) (information obtained from the author) Number randomly assigned: 501 children (1539 molars, on average 3 teeth per child) in 4 groups: 124 children in sealant, 124 in fluoride varnish, 125 in silver diamine fluoride solution, and 128 in placebo. 252 children considered in this review (sealant and placebo groups). Number evaluated: 245 (121 children in sealant group, 124 children in placebo group)
Interventions	4 treatment arms Group 1: light‐cured, fluoride releasing resin‐based sealant Clinpro Sealant (applied by a dentist). Group 2: NaF – semi‐annual application of a 5% NaF varnish (Duraphat) (applied by a dentist). Group 3: SDF – annual application of a 38% silver diamine fluoride (SDF) solution (applied by a dentist). Group 4: placebo control – annual application of water (applied by a dentist). Group 1 and group 4 considered in this review. Sealants were applied on sound permanent first molars with deep fissures or fissures with signs of early (enamel) caries viewed as wet, with opacities and discolouration. No resealing. Co‐interventions: no systemic fluoridation in the study area. 90% of the toothpastes on sale contained fluoride.
Outcomes	Sound or carious occlusal surface of molar and sealant retention status. Each molar was assessed at 2 sites (upper molar – mesial pit/fossa and distal‐palatal groove; lower molar – occlusal fissure and buccal pit/groove). Caries incidence reported as child level, tooth level and fissure site level. Outcomes were assessed by the same blinded examiner using disposable mouth‐mirrors attached to an intra‐oral LED (light‐emitting diode) light and CPI (community periodontal index) probes Adverse events
Notes	Intra‐examiner reliability: Kappa statistic over 0.9. Funding source: the Hong Kong Research Grants Council (authors were from university)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "An assistant, using computer‐generated random numbers, allocated the children individually among four groups." Comment: Adequate sequence generation
Allocation concealment (selection bias)	Low risk	A computer generated random number table (only consisting of numbers 1, 2, 3, and 4) was printed out and kept by a research assistant. The group allocation of the subject, i.e. group 1 to group 4 followed the random numbers in the random number table. The treatment was performed immediately on site by a dentist not involved in the examination of the children according to the group allocation while the research assistant was present. Additional information obtained from the author
Blinding? (Outcome assessors)	High risk	Quote: "Status of the molars, including sealant retention and development of caries into dentin (ICDAS codes 4‐6), was assessed every 6 mos by the same blinded examiner." The record forms with group assignment information of the children were kept away from the examiner by the recorder. Additional information obtained from the author. Comment: Although blinding of outcome assessor was indicated, this domain was graded as having high risk of bias because we saw that blinding of outcome assessor in clinical trials of this nature cannot be performed, as sealants are visible
Incomplete outcome data? (Caries efficacy outcomes)	Low risk	Missing data: 3/124 (2.4%) in sealant group, and 4/128 (3%) in placebo group. Comment: Marginal drop‐out rate
Selective reporting (reporting bias)	Low risk	Outcomes reported: Caries response and sealant retention. Comment: Pre‐specified outcomes (in methods) were reported in pre‐specified way
Free of other bias? Comparability of the groups	Low risk	Quote: "Proportionately more children in the sealant group than in other groups had visited a dentist or consumed snacks once a day or less (P < 0.05)." (13% of children in sealant group and 29% in placebo group consumed snacks twice or more often a day) Additional information obtained from the author that there was no statistically significant difference between the groups in the baseline caries risk of the children. The baseline mean dmft scores with SD for groups: sealant 3.19 (2.68); placebo 3.55 (2.54). Comment: We decided to grade this domain as low risk of bias although there was difference in dental visit history and consuming snacks between groups at baseline because baseline caries risk scores of the children were similar. Similar baseline caries risk level was one of the fundamental characteristics in criteria of this domain to be assessed low risk of bias
Free of other bias? Co‐interventions	Low risk	Quote: "No systemic fluoridation in the study area. 90% of the toothpastes on sale contained fluoride." Comment: This domain was graded low risk of bias because no other co‐interventions than fluoridated toothpaste were included in the protocol