Using intervention fidelity to improve behaviour change trials delivered in primary dental care

Background: Behaviour change interventions in primary dental care have produced equivocal results. Although these interventions show promise, many trials conducted by dental teams in routine practice have not shown statistically significant results, have demonstrated small effects, and have often been described as having low methodological quality. Intervention fidelity strategies can improve the reliability and validity of trials by standardising how interventions are delivered therefore improving scientific rigor. The National Institutes of Health Behaviour Change Consortium (NIH BCC) fidelity framework is especially relevant in behaviour change trials, yet little research has explored fidelity in interventions led by dental teams in primary dental care. Aim: To improve the quality of pRCTs delivered in primary dental care through the development and testing of a theoretically informed intervention fidelity strategy used in a BCI trial delivered by dental teams. Methods: I first undertook a mixed-methods study to examine dental-practice level differences in the PREFER trial, where dentists delivered risk-based behavioural messages. This study examined data from 409 trial participants, and interviews (n=16) with dental team members. Thereafter, I completed a scoping review to investigate reporting of intervention fidelity strategies in behaviour change trials in primary dental care, including articles relating to 21 interventions. Then, building on my earlier work, and using qualitative methods (53 hours of observation and 19 interviews) embedded within the RETURN feasibility trial, and using the NIH BCC framework, a theoretically informed fidelity strategy for the RETURN main trial was developed. Lastly, applying the developed fidelity strategy, I conducted a fidelity assessment of the RETURN trial, analysing 462 audio-recorded interventions sessions and interviewing 13 dental team members, focusing on the fidelity domains of training and delivery. Results: The PREFER study highlighted significant differences in trial implementation across sites and recommended the use of fidelity strategies for standardisation. The scoping review revealed intervention fidelity is underreported in dental trials, particularly in the domain of delivery. Encompassing the learning from the previous two studies, a fidelity strategy was presented pertaining to the five NIH BCC fidelity domains: design, training, delivery, receipt and enactment. After embedding the strategy, the intervention fidelity assessment found around 75% of RETURN intervention sessions were delivered with high fidelity, despite the a priori primary outcome threshold being rarely met. The dental nurse training program was consistently delivered in line with the fidelity framework, although implementation was not without its challenges. Discussion: This thesis makes key contributions to the field of pragmatic behaviour change trials delivered in primary dental care settings by: (1) emphasising the critical role of intervention fidelity in the field which has paid little attention to the concept, (2) making contextually specific recommendations about how to increase intervention fidelity and (3) providing the first comprehensive fidelity assessment of a behaviour change trial delivered by dental nurses, which will contextualise the upcoming results of the RETURN trial. Implications for dental behaviour change trials and future research directions are also discussed.