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.

The primary and secondary outcome of this study was new root caries and arrested root caries. A root surface with new caries experience was recorded when a root surface which was sound at baseline was found to have a carious lesion or a filling at a follow-up examination. Arrested root caries was recorded when the active root caries found at baseline changed into inactive root caries at follow-up. The status of each root surface was recorded using the codes recommended by the International Caries Detection and Assessment System (ICDAS Ⅱ) Coordinating Committee in 2009.

A mean root caries increment of around 0.8 root surface per year of control group was reported in a previous clinical trial conducted in Hong Kong. Thus, in this study, a 24-month increment of 1.6 new decayed root surfaces and a standard deviation of 2 was anticipated. In order to show that a 50% difference in mean caries increment between the test and control groups was statistically significant using a 2-sample t-test at a 5% significance level and at an 80% power, a sample size of 100 subjects in each group was required. Allowing for a drop-out rate of 20% over 24 months, a total of 480 subjects (120 in each group each site) were needed.

Inclusion Criteria:

1. have at least 5 teeth with exposed root surfaces and not indicated for extraction, and
2. living in the community and have self-care ability for normal daily activities.

Exclusion Criteria:

1. have life-threatening or serious health problems,
2. have cognitive problems in communication or in receiving oral hygiene instructions
3. have salivary gland diseases or received radiotherapy in the head and neck region.

Will consider individual request case by case