
Introduction: Dental caries remains a significant public health problem and investment in multi-level oral health promotion intervention is essential. The effects of this type of intervention are only partially known; thus, further evidence is needed. Objectives: This article describes the design, protocols, and baseline characteristics of centers and participants (caregiver/child dyads) involved in a multi-level oral health promotion cluster randomized controlled intervention integrated into Primary Healthcare Centers (PHCs) in Brazil. Methods: Two PHCs, and by extension 170 caregiver/child dyads, were allocated to an intervention condition, and two PHCs and 174 caregiver/child dyads were allocated to a no treatment control condition (usual care). The intervention targets intra- and interpersonal (child, family) and organizational (PHC) level factors associated with oral health outcomes. These outcomes include caregivers’ and children’s oral health quality of life, children’s dental caries and oral health-related behaviors. Caregivers’ behaviors, psychosocial factors, oral health knowledge and PHCs’ oral health promotion practices will be examined as potential mediators of intervention effects. The baseline survey and dental examinations occurred in 2015. Two post-intervention follow-ups occurred, the first at 12 months, and the second at 24 months from baseline. Results: No baseline differences were observed between the conditions on socioeconomic and demographic characteristics, oral health quality of life, children’s dental caries and PHCs’ oral health practices. Some children’s behaviors, as reported by their caregivers, differed statistically between conditions at baseline. Favoring the control condition were tooth brushing twice a day (44.5% versus 28.2%), low/moderate sugar consumption (54.6% versus 41.8%) and use of dental services (33.5% versus 21.2%). Conclusion: This trial seeks to broaden understanding of how to prevent dental caries in young children among low-income families with low access and use of dental services. Identification of intervention mediators will inform future efforts in this area.