Villa 1997.

Study characteristics
Methods	Location: USA Setting: secondary care No mention of funding or ethical approval
Participants	Children aged 8 to 18 yrs Participants were selected following screening "Twenty‐four patients between the ages of 6 and 18 years with digit‐sucking habits were selected within a 4‐month screening period from the patient population at Montefiore Medical Center, Division of Orthodontics, for inclusion in this study." Digit suckers 24 recruited and analysed
Interventions	Palatal crib therapy There was no mention of the specific design of this appliance therefore it was assumed it was similar in design to that described by Haryett and Larsson (n = 12). Control This group received no treatment (n = 12) Pretreatment records were taken for the participants and included study models, OPT, lateral cephalogram radiographs, and intra and extra oral photographs. After 3 months, study models were again taken and compared with the pretreatment ones.
Outcomes	1. Reduction in anterior open bite, in mm, calculated by comparing measurements from the pre and post intervention study models 2. Reduction in overjet, in mm, calculated by comparing measurements from the pre and post intervention study models 3. Change in arch length, in mm, calculated by comparing measurements from the pre and post intervention study models
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"assigned randomly"
Allocation concealment (selection bias)	Unclear risk	Method of concealment was not described
Blinding of participants and personnel (performance bias) Patient	High risk	Blinding of child participant not possible
Blinding of participants and personnel (performance bias) Operator	High risk	Blinding not possible
Blinding of outcome assessment (detection bias) All outcomes	Low risk	"The evaluator was blinded as to group status of each study model."
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Drop‐out rates were not reported, although it was implied that all children were followed up. The results section states "Overall 10 males and 14 females were studied."
Selective reporting (reporting bias)	Low risk	Outcomes were clearly defined and all reported.
Other bias	Unclear risk	Patients were recruited from an orthodontic department patient population. Unclear if sample would be representative of general population.

yrs = years