This quasi-experimental study evaluates a mosque-based oral health education intervention ("Smile With Prophet", SWP) among adult male mosque attendees in Dhaka, Bangladesh, using a Solomon four-group design.

A total of 142 participants were enrolled across two mosques (intervention and control). The analytical sample comprises 80 adult male attendees (≥18 years) allocated to four groups: intervention and control, each with pretest-posttest and posttest-only arms (n=20 per group).

The SWP intervention consists of oral health education delivered through Friday sermons (khutbas), supported by educational leaflets and provision of miswak. Outcomes are measured at baseline and 3-week follow-up and include oral health knowledge (14-item questionnaire), self-reported tooth brushing practices (15-item questionnaire), and clinical plaque scores (Greene-Vermillion Simplified Oral Hygiene Index, reversed).

The primary objective is to evaluate the effect of the intervention on knowledge and plaque scores. The secondary objective is to assess self-reported practice changes.

Study design: Quasi-experimental study using a Solomon four-group design conducted in two mosques in Dhaka, Bangladesh, between January and December 2022.

Participants: A total of 142 adult male mosque attendees (≥18 years) who attended three consecutive Friday congregational prayers were enrolled. Of these, 119 completed baseline assessment (pretest questionnaire and clinical plaque examination). Across the three-week study period, 80 participants completed all required follow-up assessments and are included in the final analysis (40 intervention, 40 control). Participants were allocated to four groups: intervention and control, each with pretest-posttest and posttest-only arms (n=20 per subgroup).

Intervention: The "Smile With Prophet" (SWP) intervention comprises: (1) oral health education delivered through Friday sermons (khutbas) integrating scientific evidence with Islamic teachings (Sunnah); (2) educational leaflets for take-home reinforcement; (3) provision of miswak (traditional tooth cleaning stick); and (4) a dental health campaign with clinical examination. The control group receives standard khutbas without oral health content; the intervention is provided after study completion.

Statistical analysis: Non-parametric tests will be used for data that are not normally distributed (Kolmogorov-Smirnov test). Mann-Whitney U tests will compare groups; Wilcoxon signed-rank tests will assess within-group changes; Kruskal-Wallis tests will compare all four Solomon groups simultaneously. The Solomon four-group design controls for pretest sensitisation. Attrition analysis will compare baseline characteristics of retained versus lost participants.

Inclusion Criteria:

• Respondent is willing to participate and gives consent.
• Respondent is aged 18 years or older.
• Respondent attends weekly congregation prayers at the selected mosque.

Exclusion Criteria:

• Respondent is mentally unstable or unable to understand the intervention (e.g., too old or cognitively impaired).

3.12.1 Hiring Doctors: None of the doctors were used for second time for data collection campaigns to avoid examiners bias. A total of 10 doctors are hired for four dental check-up (pre and post test in intervention & control mosques).

But they were not informed about the objectives of the study and whether the mosque was an intervention or control mosque, or whether the campaign was baseline data collection or for follow up data

3.2.1 Mosque Agreement: Written informed consent was obtained from heads of the mosque Committees or from imams or khatibs for their and their mosques' participation after describing required data collection procedures (without disclosing the desired objectives hypothesis of the study thus masking the intention)

• Privacy and confidentiality were maintained strictly, as each of the participants was assessed separately and the dentist examined the participants with in a screened compartment of the mosque.