Raadal 1984.

Methods	Trial design: split‐mouth design, sealant tooth randomly assigned Follow‐up: average 23 months
Participants	Location: Study setting was a public dental clinic in a small town in Norway Inclusion criteria: Children had to have 1 recently erupted homomaxillary pair of permanent first molars. Occlusal surface was sound or had initial caries in enamel Age at baseline: 6 to 9 years Gender: 62 girls, 59 boys Baseline caries: mean dmft 4.7 (SD 3.3) Number randomly assigned: 121 children with total of 210 tooth site pairs (110 in maxilla and 100 in mandible; in maxilla, mesial and distal portions of occlusal surface were treated separately) Number evaluated: No description of drop‐outs regarding children was provided, but information provided indicates that 208 of 210 sealed sites were evaluated (meaning that 1 child or 2 children were dropped out)
Interventions	Comparison: resin‐based fissure sealant vs fluoride varnish Tooth pair: occlusal surface of 1 tooth sealed with autopolymerised resin‐based Concise; on occlusal surface of the other tooth of the tooth pair, fluoride varnish (Duraphat, sodium fluoride (NaF)) was applied No information was provided on proportions of sound surfaces and teeth with enamel lesions. Surfaces with initial caries in enamel were opened mechanically and caries removed before sealant application (Quote from the article: "In those cases where caries had progressed to the dentin, conventional cavities for amalgam fillings were prepared, and these cases were excluded from the study") No resealing Surfaces to be painted with fluoride varnish were treated every 6 months Co‐interventions: annual information and motivation about dental care; fluoride tablets recommended; fluoride rinsing with 0.5% NaF solution at school
Outcomes	Sound or carious occlusal surface of molar Caries status was recorded using visual‐tactile method and bitewings
Notes	Complete sealant retention 63% at 23 months Funding source: no information on funding
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Coin tossing. Additional information was obtained from study author Comment: Random sequence generation was adequate
Allocation concealment (selection bias)	Low risk	Comment: Random sequence was adequately concealed up until the moment of allocation by flipping a coin to allocate a particular tooth, within a tooth pair, to be sealed
Blinding of outcome assessor (detection bias)	High risk	No blinding of the outcome assessor was performed Comment: Additional information was obtained from study author
Incomplete outcome data (attrition bias) All outcomes	Low risk	Drop‐out rate 1% for tooth site pairs after 23 months (no description of drop‐outs was provided regarding children, but information indicates that 208 of 210 sealed sites were evaluated, meaning that 1 child or 2 children were dropped out). No reasons for drop‐outs were described Comment: marginal drop‐out rate
Selective reporting (reporting bias)	Low risk	Outcomes reported: incidence of dentinal carious lesion on treated occlusal surfaces of molars (yes or no) at 23 months of follow‐up, retention Comment: Pre‐specified caries outcomes (in methods) were reported in the pre‐specified way
Other bias	Low risk	Comparability of groups: Comment: Split‐mouth design, which included sound surfaces or surfaces with enamel lesions. With split‐mouth designs, we saw that both surfaces within a tooth pair in any case will eventually be at equal risk for caries because of the long follow‐up (regardless of whether the diagnosis consisted of a sound surface or a surface with an enamel lesion) Co‐interventions: Annual information and motivation about dental care; fluoride tablets recommended; fluoride rinsing with 0.5% NaF solution at school Comment: split‐mouth design. Conditions are the same for both teeth within a tooth pair