This repository contains the full dataset from a multicentre non-inferiority randomised clinical trial with 2 years of follow-up, comparing the success rate (primary outcome) and several secondary outcomes of primary molars treated with a simplified non-instrumentation pulpectomy technique versus a conventional instrumentation approach. The dataset is fully anonymised and includes information on treatment allocation, study centre, participants' age and sex, baseline characteristics of the included teeth, initial diagnosis, and all primary and secondary outcomes. Secondary outcomes include children's discomfort and behaviour during treatment, clinical chair time, postoperative events, oral health-related quality of life measures, and other patient-centred outcomes. An additional spreadsheet contains a complete data dictionary describing all variables and coding schemes used in the study, as well as detailed information regarding treatment failures and their respective reasons.