. Background Dental caries remains the major oral health challenge affecting more than half of adolescents globally. Most of the disease remain untreated, therefore, negatively impacting adolescents’ general health, well-being, and quality of life. Basic Package of Oral Care (BPOC) is a potential solution to the challenge, however, evidence on its effectiveness is scarce. This study primarily assessed the effects of applying modified BPOC on dental caries prevalence and secondarily on knowledge and behaviours related to dental caries among adolescents in Copperbelt Province, Zambia. Methods A parallel arms cluster randomized field trial (Reg-PACTR202210624926299) including 22 public secondary schools in Copperbelt province, Zambia, was carried out between January 2021 and March 2023. A pre-tested questionnaire was used to collect socio-demographics, knowledge and dental caries related behaviours data, while dental caries was assessed clinically using the caries assessment spectrum and treatment (CAST) at baseline and the follow-ups. The 1st and 2nd follow ups were conducted at 18-and 24 months after baseline respectively. The analysis was based on intention-to-treat protocol using generalized estimating equations (GEE) and results are reported as OR (95% CI). Results Out of 1,794 participants at baseline, 1,690 (94.2%) and 1,597 (89.0%) were seen at 1st and 2nd follow ups respectively. A significant interaction (BPOC x time) for dental caries models at 18 months and 24 months was observed. Secondary outcomes with significant interactions included adequate knowledge models at 18 months and 24 months as well as use of fluoridated toothpaste twice or more per day at 18 months and 24 months . Subgroup analysis showed that the intervention group had better outcomes than the control group in terms of dental caries prevalence, adequate knowledge, use of fluoridated toothpaste twice or more per day, at 18- and 24 months. Conclusion The modified BPOC was effective in reducing prevalence of dental caries, improving knowledge on dental caries, and the frequency of using fluoridated toothpaste among Zambian adolescents. Further studies need to be conducted in order to address other factors affecting oral health related behaviours such as the school and home environment, social and cultural factors.

The authors have declared no competing interest.

The trial was registered by Pan African Clinical Trial Registry (PACTR202210624926299) available at https://pactr.samrc.ac.za/TrialDisplay.aspx?TrialID=24046.

https://pactr.samrc.ac.za/TrialDisplay.aspx?TrialID=24046.

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The study received ethical approval from three institutions: the study site (Tropical Diseases Research Centre, Zambia -IRB 00002911 FWA 00003729), training institutions (MUHAS Institutional Review Board, Tanzania -P. MUHAS-REC-4-2020-208), and the Regional Ethical Committee vest 191836, Norway). The appropriate authorities granted permission to conduct the research, and participation was entirely voluntary. Only adolescents who assented and had parental written informed consent were enrolled.

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