Boyd 2021.

Study characteristics
Methods	RCT, parallel groups Follow‐up: 1 and 2 years Setting: primary care in Whanganui, New Zealand
Participants	Unit of randomisation: teeth 295 children, 570 carious primary teeth analysed for both arms Age: 3–8 years Inclusion criteria: children aged 3–8 years attending for their next dental examination from 37 schools and preschools; no medical history; radiograph: ≥ 1 radiographically detectable proximal carious lesion in the primary molars, with healthy pulp and with a score of P3 or P4 in the following radiographic scoring system: P0, no radiolucency; P1, radiolucency in outer half of enamel; P2, radiolucency in inner half of enamel; P3, radiolucency < 0.5 mm into dentine; P4, radiolucency > 0.5 mm into dentine but confined to dentine's outer half; teeth had to have more than half the root structure remaining. If a child had > 1 tooth affected by a proximal lesion, > 1 tooth was included Exclusion criteria: unable to have radiographs taken; no carious lesions present or into dentine at the P3 or P4 level; medically compromised; no parental consent or did not assent to participation in the study
Interventions	2 treatment arms Group 1 (149 children, 273 teeth): HT: procedure conducted in line with Innes 2011. Separating elastics were provided for dental therapists to use prior to the HT when needed. An SSC was placed without any carious tissue removal or tooth preparation. Group 2 (146 children, 297 teeth): SE: included tooth preparation with SE, which included SSC, amalgam, composite or glass ionomer cement restorations.
Outcomes	Success or failure based on clinical and radiographic measures combined at 1‐ and 2‐year follow‐up to give composite outcomes of success, minor failure or major failure as defined by Innes 2007. Success: restoration appeared satisfactory, no intervention required no clinical signs or symptoms of pulpal pathology no pathology visible on radiographs Major failure irreversible pulpitis/abscess requiring pulp treatment or extraction inter‐radicular radiolucency restoration lost, pulpally involved and tooth unrestorable Minor failure restoration lost but restorable secondary or new carious lesion restoration worn and needing intervention ectopic first permanent molar adjacent to crowned tooth
Notes	There was clustering of multiple teeth per participant. Participant follow‐up rate at 12 months was 95% and at 24 months was 91%. Study funded by a grant from Cure Kids New Zealand, and stainless‐steel crowns and cement were provided by 3M.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	No information and no prepublished protocol to check. No data in the trial registration. Quote: "with children randomized to intervention with either the HT or NHT upon recruitment to the study."
Allocation concealment (selection bias)	Unclear risk	No information and no prepublished protocol to check. No data in the trial registration.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Unable to blind participants or personnel because of types of intervention – visibly different.
Blinding of outcome assessment (detection bias) All outcomes	High risk	Unable to blind outcome assessor because of types of intervention – visibly different.
Incomplete outcome data (attrition bias) All outcomes	Low risk	All teeth in trial accounted for.
Selective reporting (reporting bias)	Unclear risk	No published protocol.
Other bias	Low risk	No other biases detected.