Raadal 1984.

Study characteristics
Methods	Trial design: split‐mouth, sealant tooth randomly assigned Follow‐up: mean 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: 6–9 years Sex: 62 girls, 59 boys Baseline caries: mean dmft 4.7 (SD 3.3) Number randomly assigned: 121 children with 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 dropouts regarding children provided, but information provided indicated that 208/210 sealed sites were evaluated (meaning that 1 child or 2 children had dropped out)
Interventions	Comparison: resin‐based FS vs FV Tooth pair: occlusal surface of 1 tooth sealed with autopolymerised resin‐based Concise; on occlusal surface of the other tooth of the tooth pair, FV (Duraphat, sodium fluoride) 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 FV were treated every 6 months Co‐interventions: annual information and motivation about dental care; fluoride tablets recommended; fluoride rinsing with 0.5% sodium fluoride solution at school
Outcomes	Primary outcome Dental caries – sound or carious occlusal surface of molar Caries status was recorded using visual‐tactile method and bitewings
Notes	Inter‐rater agreement: not considered Complete sealant retention: 63% at 23 months Funding source: no information
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 participants and personnel (performance bias) All outcomes	Low risk	Blinding not possible as sealants could be seen; however, we judged it to be unlikely to be a significant source of bias in a study with a split‐mouth design.
Blinding of outcome assessor (detection bias)	High risk	No blinding of the outcome assessor performed. Comment: additional information obtained from study author.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Dropout rate 1% for tooth site pairs after 23 months (no description of dropouts was provided regarding children, but information indicated that 208/210 sealed sites were evaluated, meaning that 1 child or 2 children dropped out). No reasons for dropouts described. Comment: marginal dropout 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: prespecified caries outcomes (in methods) were reported in the prespecified 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 considered 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% sodium fluoride solution at school. Comment: split‐mouth design. Conditions are the same for both teeth within a tooth pair.