Background: There is a lack of evidence for the effective management of dental caries in children's primary teeth. The trial entitled 'Filling Children's Teeth: Indicated Or Not?' (FiCTION) was designed to examine the clinical and cost effectiveness, in primary dental care, of three different approaches to the management of caries in primary teeth. However, before the FiCTION main trial commenced, a pilot trial was designed. Service provider (dentists and other members of the team including dental nurses and practice managers) and participant (child participants and their parents) involvement was incorporated into the pilot trial. The aim of this study is to describe service providers' and users' perspectives on the pilot trial to identify improvements to the conduct and design of the FiCTION main trial.Methods: Qualitative interviews (individual and group) were held with dentists, dental team members, children and parents involved in the FiCTION pilot trial. Individual interviews were held with four dentists and a group interview was held with 17 dental team members. Face-to-face interviews were held with four parents and children (four- to eight-years old) representing the three arms of the trial and five telephone interviews were conducted with parents. All interviews were transcribed verbatim. Framework analysis was used.Results: Overall, service providers, children and parents found the pilot trial to be well conducted and an interesting experience. Service providers highlighted the challenges of adhering to research protocols, especially managing the documentation and undertaking new clinical techniques. They indicated that the time and financial commitments were greater than they had anticipated. Particular difficulties were found recruiting suitable patients within the timeframe. For parents recruitment was apparently more related to trusting their dentist than the content of information packs. While some of the older children understood what a study was, others did not understand or were not aware they were enrolled.Conclusions: The findings provided valuable recommendations to improve the method of recruitment of dental practices and patients, the timing and content of the training, the type of support dentists would value and ways to further engage children and parents in the FiCTION main trial.Trial registration: ISRCTN77044005.