Mertz‐Fairhurst 1998.

Study characteristics
Methods	RCT, split‐mouth design Duration of study: 24 months. Follow‐up: 10 years; assessment intervals 6 months, and 1, 2, 3, 4, 5, 6, 9 and 10 years Setting: School of Dentistry, Medical College of Georgia, Augusta, GA, US; treatment performed by faculty members
Participants	123 participants, 156 pairs of molar or premolar teeth (312 teeth) Age: 8–52 years; median 23 years Inclusion criteria: each person must have had at least 1 pair of Class I lesions in premolars or permanent molars, and the carious lesions must have been clinically and radiographically (outer half of dentine) obvious
Interventions	3 treatment arms (we combined groups 1 and 2) Group 1 (79 teeth): CR: unsealed amalgam AGU: rubber dam when possible. It was prepared using the traditional principles for Class I cavity form in which the preparation was extended into non‐carious fissures to prevent future caries activity (extension for prevention). Complete removal of soft demineralised dentine and chalky white demineralised enamel. Amalgam placement. Group 2 (77 teeth): CR: sealed amalgam restoration: rubber dam when possible. Removed all soft demineralised dentine only in the localised area of the carious lesion, but the preparation was not extended into unaffected fissures and grooves. If 2 separate occlusal lesions were present, they were not combined into a single larger amalgam restoration. Instead, 2 small localised cavity preparations were made, except when the distance between the 2 cavity preparations would be < 0.5 mm. After the amalgam was placed, the operator applied sealant over the restoration and all pits and fissures of the tooth. Group 3 (156 teeth): caries sealing using composite (CompS/C): rubber dam when possible. The only preparation for the CompS/C restorations consisted of placing a 45‐ to 60‐degree bevel in the enamel surrounding the frank cavitated lesion. This occlusally divergent bevel had to be ≥ 1 mm wide and placed in sound enamel. The operator removed all the crumbly, opaque demineralised enamel with a bur until they reached translucent sound enamel. They did not remove undermined enamel or caries below the bevel. After restoration and a final shaping of the occlusal anatomy with rotary instruments, the operator etched all the occlusal, buccal and lingual pits and fissures for 60 seconds, washed the etchant thoroughly and applied a chemically cured sealant. The sealant, which was applied with an applicator supplied in the sealant kit, was placed over the entire restoration and adjacent etched enamel as well as over all the pits and fissures of the tooth.
Outcomes	Restorations clinically failed or marginal integrity failure; restoration integrity.
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Treatment assignment was statistically randomised for each study tooth using a randomisation list prepared by a statistician.
Allocation concealment (selection bias)	Unclear risk	No information on how allocation concealment was carried out.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Not possible to blind operators as treatments were different. Unclear about participants.
Blinding of outcome assessment (detection bias) All outcomes	High risk	Double‐blind examiners for radiographic examinations. Other not described, but difficult to blind different materials.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Reasons for attrition not always clear.
Selective reporting (reporting bias)	High risk	Unclear whether all outcomes were fully reported.
Other bias	Unclear risk	Data were not presented in same manner throughout, so unclear in places.