This study was a randomized clinical trial lasting for 24 months in two study sites, Hong Kong (water fluoridated) and Guangzhou (non-fluoridated area). A total of 534 subjects will be recruited from elderly social centers located in different districts in the two study sites (260 & 274). Baseline clinical examination was conducted by a single calibrated examiner in the social centers using an intra-oral LED light, mouth mirrors and probes. Subjects were randomly allocated into two study groups and receive interventions accordingly. Follow-up examinations at 6-month intervals were carried out to assess the clinical outcomes, i.e. whether new root caries developed and whether the active root caries found at baseline become arrested. Results of this study could provide the much needed evidence to guide the dental professionals in Hong Kong and China, and possibly worldwide in deciding on the most appropriate intervention for the prevention and management of this common dental disease of the older adults.