Yazdani 2009

Methods	Study design: cluster‐randomised controlled trial Conducted in: Iran Unit of randomisation: school class Unit of analysis: individual Setting: public schools in Tehran Funded by: not disclosed Duration of the study: 12 weeks
Participants	Inclusion criteria: not reported (public schools) Exclusion criteria: not reported Age at baseline: 15 years N (baseline): 417 N (controls baseline): 130 N (controls follow‐up): 123 N (interventions baseline): total n = 287 Group 1 (leaflet) = 148 Group 2 (videotape) = 139 N (interventions follow‐up): total n = 265 Group 1 (leaflet) = 135 Group 2 (videotape) = 130 Recruitment: selection of schools from a list provided by the Head Office for Education of Tehran Gender: n = 205 boys, n = 212 girls at baseline
Interventions	Intervention: Intervention was based on exposing students to oral health knowledge through a leaflet and a videotape designed for this study. Educational key messages were the same in both materials: the importance of oral health, the role of microbial plaque, frequency and methods of proper toothbrushing and flossing, importance of regular dental attendance, a healthy diet and proper use of fluorides Group 1 (leaflet): The leaflet was pocket sized with coloured pictures and illustrations for each topic to maintain the student’s attention and interest. It was delivered to the leaflet group twice: at baseline and at the sixth week of the intervention period Group 2 (videotape): The videotape was a 17‐minute film shown in the classroom. It was presented twice: at baseline and at the sixth week of intervention Control: The control group underwent the dental examination but received no educational intervention at all Duration of intervention: 12 weeks
Outcomes	Dental plaque, gingival bleeding
Implementation related factors	Theoretical basis: not reported Resources for implementation: Producing educational materials for this study was inexpensive: for the leaflet, 2000 Rials (0.15 €) each, and for the videotape, 3000 Rials (0.2 €) per student, along with clinical equipment for examinations Who delivered the intervention: Interventions were carried out in co‐operation with school authorities and volunteer teachers PROGRESS categories assessed at baseline: not reported 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: Producing educational materials for this study was inexpensive: for the leaflet, 2000 Rials (0.15 €) each, and for the videotape, 3000 Rials (0.2 €) per student
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	At each of the 14 schools, among 2 to 5 classes of 15‐year‐olds, 1 class was selected randomly. Then, 14 classes (n = 417; boys, n = 205; girls, n = 212) were randomly divided into 3 groups: a leaflet group (2 boys' classes and 3 girls' classes, n = 148), a videotape group (3 boys' classes and 2 girls' classes, n = 139) and a control group (2 boys' classes and 2 girls' classes, n = 130)
Allocation concealment (selection bias)	Low risk	All clusters were randomised at the same time
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Unclear
Selective reporting (reporting bias)	Low risk	Published report presents all expected outcomes of interest to the review
Other bias	High risk	Allocated to classes that were closely located, and contamination was likely to occur
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Students were unaware in advance of examination and intervention dates
Blinding of outcome assessment (detection bias) All outcomes	Low risk	At baseline 1 of the study authors and at follow‐up another experienced blinding of dentist to study groups when clinical examination was carried out

¹DMFT = Decayed, Missing and Filled Teeth

²deft = decayed, extracted and filled teeth

³ECC = early childhood caries

⁴S‐ECC = severe early childhood caries

⁵SES = socioeconomic status

⁶dmft = decayed, missing and filled teeth

⁷OHE = oral health education

⁸MI = motivational interview

⁹HPS = health promoting schools

¹⁰WHO = World Health Organization

¹¹EHCP = Essential Health Care Programme

¹²DMFS = Decayed, Missing and Filled Surfaces

¹³dmfs = decayed, missing and filled surfaces

¹⁴DHE = Dental Health Education

¹⁵OH = oral health

¹⁶WIC = Women, Infants and Children Supplemental Food Programmes

¹⁷SDT = self‐determination theory