© 2018 Gerodontology Association and John Wiley & Sons Ltd Objectives: The purpose of this study was to test the efficacy of MOUTh (Managing Oral Hygiene Using Threat Reduction), a nonpharmacologic, relationship-based intervention vs. control on 2 primary outcomes for nursing home (NH) residents with dementia who resisted mouth care: (i) reduction in the occurrence and intensity of care-resistant behaviours (CRBs) and (ii) improvement in oral health. Two secondary outcomes were also examined: (i) the duration of mouth care and (ii) the completion of oral hygiene activities. Background: Persons with dementia who exhibit CRBs are at risk for inadequate mouth care and subsequent systemic illnesses. Materials and methods: The study used a randomised repeated measures design. Recruitment occurred in 9 nursing homes that varied in size, ownership, reimbursement patterns and location. One hundred and one nursing home residents with dementia were randomised at the individual level to experimental (n = 55) or control groups (n = 46). One hundred participants provided data for the analyses. Results: Compared to the control group, persons in the experimental group had twice the odds of allowing mouth care and completing oral hygiene activities; they also allowed longer duration of mouth care (d = 0.56), but showed only small reductions in the intensity of CRBs (d = 0.16) and small differential improvements in oral health (d = 0.18). Conclusion: The data suggest that this intervention facilitates mouth care among persons with dementia. The management of refusal behaviour may be a clinically more realistic approach than reducing or eradicating refusals.