The Children's Oral Health Initiative (COHI) is a federally funded community-based preventive dental programme implemented in geographically remote Canadian Indigenous communities. The study investigated the effect of the availability of local community health workers (COHI Aides) on access to the programme's preventive dental services for children. Twenty-five communities were continuously enrolled in the COHI during the 7-year study period. Communities were categorized as having uninterrupted (all 7 years), intermittent (≥4 years) or sporadic (<4 years) service from a community health worker. Four outcome variables measured longitudinal changes in access to preventive dental services: (i) the number of enrolments; (ii) the number of enrolled children with multiple fluoride varnishes delivered; (iii) the number of enrolled children with sealants placed; and (iv) the number of enrolled children receiving ART. The general longitudinal trend for programme enrolment and each of the preventive dental service delivery outcomes was similar. Children in communities with uninterrupted service tended to have the highest rates of enrolment and service delivery, which remained constant over time. Children in communities with sporadic service tended to have persistently low rates of enrolment and service delivery over the study period. Community health workers were beneficial in promoting programme enrolment, as well as facilitating and augmenting the delivery of preventive dental services. © 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.