Process evaluation of a complex intervention to improve the oral health of nursing home residents (MundZaRR): a multimethod study

Background The oral health of nursing home residents is often poor. In the cluster-randomised controlled MundZaRR trial, a complex intervention to improve oral health was investigated across 18 nursing homes ( n = 271 participants). A comprehensive process evaluation aimed to explore the experiences of various target groups and gain insights into the implementation of the intervention. Methods The process evaluation followed international guidelines. The study was conducted in Germany and the data collection took place between July 2022 and October 2023 and comprised 23 individual, semi-structured interviews and three focus groups with dentists, dental assistants, nursing home managers and staff, and members of the resident council, 20 participatory observations, written surveys, structured protocols and document analysis. Quantitative data were analysed descriptively; qualitative data were analysed using content analysis. Results Three educational training courses over approximately nine hours for dentists and dental assistants were performed largely as planned and evaluated positively. The intervention could not be implemented in one out of nine nursing homes due to staff and time shortages, and the remaining intervention clusters showed considerable variations in implementation fidelity and cooperation between dental assistants and nursing home staff. Participatory observations revealed that individual oral care recommendations were only completely implemented in around half of the observed participants and that more specific oral care measures (e.g., interdental cleaning) were only rarely performed. The main barriers to the intervention’s implementation were staff and time shortages, lack of interest or engagement of nursing staff, and individual resident barriers (e.g., poor health condition, uncooperative behaviour). The COVID-19 pandemic posed a major challenge during the recruitment phase, but predominantly did not affect the further course of the study, according to the participating target groups. Conclusion Despite the overall positive perception of the intervention concept by the target groups, we found several inconsistencies in the implementation across the nursing homes of the intervention group. The barriers identified can provide indications for the future development and implementation of comparable oral health interventions in the nursing home setting. Trial registration ClinicalTrials.gov (Trial registration number NCT04140929). Registered on 24 October 2019, https://clinicaltrials.gov/study/NCT04140929 .