Using mHealth to promote parents' brushing of preschool children's teeth: a protocol for a randomized factorial trial using the Multi-phase Optimization Strategy (MOST).

Background: Early childhood caries is a highly prevalent disease affecting young children. Parental brushing of children's teeth is recommended during preschool years. Interventions to promote parental brushing of children's teeth are assessed as a package in randomized clinical trials and the efficacy of separate components is not known.