Pakpour 2014

Methods	Study design: cluster‐randomised controlled trial Conducted in: Qazvin, Iran Unit of randomisation: schools Unit of analysis: individual Setting: high schools Funded by: "The study was supported by the Department of Public Health at Qazvin University of Medical Sciences. One of the authors (Sniehotta) is funded by Fuse, the Centre for Translational Research in Public Health, a UKCRC Public Health Research Centre of Excellence. Funding for Fuse was from the British Heart Foundation, Cancer Research UK, Economic and Social Research Council, Medical Research Council, the National Institute for Health Research, under the auspices of the UK Clinical Research Collaboration" Duration of the study: 24 weeks
Participants	Inclusion criteria: Adolescents were eligible if they had not participated in any previous type of oral health education and promotion programmes and had not received orthodontic treatment Exclusion criteria: not reported Age at baseline: 15 years old N (controls baseline): 122 N (controls follow‐up): 122 N (gain‐frame intervention group baseline): 124 N (gain‐frame intervention group follow‐up): 124 N (loss‐frame intervention group baseline): 126 N (loss‐frame intervention group follow‐up): 126 Recruitment: Investigators randomly selected 1 class in each school to participate in the study. All students in selected classes participated in the study Gender Gain‐framed OHE: male = 46.8%, female = 53.2% Loss‐framed OHE: male = 51.6%, female = 48.4% Control: male = 48.4%, female = 51.6%
Interventions	Two intervention groups and 1 control group Interventions were gain‐framed pamphlets that delivered 6 positive messages about oral health Loss‐framed intervention delivered 6 negative messages about oral health Control group received no intervention Duration of intervention: 30 minutes
Outcomes	Periodontal health Plaque index
Implementation related factors	Theoretical basis: not reported Resources for implementation: not reported Who delivered the intervention: unclear PROGRESS categories assessed at baseline: gender, education, SES PROGRESS categories analysed at outcome: not reported Outcomes related to harms/unintended effects: not reported Intervention included strategies to address diversity or disadvantage: not reported Economic evaluation: not reported
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Schools were divided into zones, then were randomised. In each school, 1 class was randomly selected to participate, and all students in selected classes participated in the study
Allocation concealment (selection bias)	Low risk	All clusters were randomised at the same time
Incomplete outcome data (attrition bias) All outcomes	Low risk	Dropout rate was small (n = 17, 4.5%) owing to school absence
Selective reporting (reporting bias)	Low risk	Published article includes all expected outcomes
Other bias	Unclear risk	Unclear
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Two trained dentists blinded to group allocation performed oral examinations in the classroom
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Unclear