Motivational interviewing effects on caries prevention in children differ by income: A randomized cluster trial

Objectives: This study aimed to investigate the differential preventive effect of motivational interviewing (MI) on early childhood caries (ECC) according to socioeconomic variables, using a community-based trial in a public healthcare setting. Methods: A cluster-randomized, double-blind study with two parallel groups in healthcare clinical settings (HCCs) comparing conventional oral health education (CE) and MI aimed at mothers of children born in 2013 and 2014. The oral health team of 6 of the 12 HCCs were trained in MI. This training was intensive for active learning of the basic MI principles, conducted by a psychologist who is a PhD in psychiatry and has extensive experience in conducting MI training workshops. It was held in an experiential format divided into two 4-hour shifts, with a 1-week interval. Children who attended at least one dental visit in the first year of life at their HCC were clinically evaluated by trained examiners and parents responded to a questionnaire. The effect of MI on the caries outcome compared with CE was evaluated in different subgroups: family income, mother's education and skin colour. Results: One hundred and eighty-six were included in the CE group and 228 in the MI group. The caries rate per 100 surface-year was 1.29 (95%CI: 0.92-1.80) in the CE group and 0.46 (95%CI: 0.29-0.73) in the MI group. The effect of MI was statistically significant in the lower-income category (P =.03); MI prevented 57% of carious lesions (IRR = 0.43, 95% CI 0.22-0.83) and reduced the occurrence of the disease on more than one surface per 100 followed surface-year in this same category in the equivalent income subgroup (IRD = −1.37, P =.04). Conclusions: Motivational interviewing had a greater preventive effect against caries in children whose families are of lower income.