Conditions: Dental Caries
Allocation: RANDOMIZED | Intervention model: PARALLEL
Enrollment: 323
Healthy volunteers: yes

Brief summary:
This study is a randomized clinical trial lasting for 30 months. A total of 300 subjects will be recruited from social centres for elders located in different districts in Hong Kong. Baseline clinical examination will be conducted by a single calibrated examiner in the social centres using an intra-oral LED light, mouth mirrors and probes. Subjects will be randomly allocated into the three study groups and receive interventions accordingly. Follow-up examinations at 6-month intervals will be carried out to assess the clinical outcomes, i.e. whether new root caries has developed and whether the active root caries found at baseline have become arrested (remineralized and hardened) or not. Photographs of the arrested lesions will be taken to assess their colour. Results of this study will provide the much needed evidence to guide the dental professionals in Hong Kong and worldwide in deciding on the most appropriate intervention for the prevention and treatment of this common dental disease of the older adults.

Detailed description:
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. Color of the arrested root caries lesion was classified into one of four types according to PANTONE® color plates placed next to the lesion (Fig 1), namely yellow (7401U), light brown (1245U), dark brown (4635U), and black (Black U).

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 30-month increment of 2 new decayed root surfaces was anticipated. The ratio of the mean to the standard deviation of the root caries increment was expected to be around 1:1.5. In order to show that a 50% difference in mean caries increment between the highest and the lowest values in the three groups was statistically significant at a 5% significance level and at an 80% power, 80 subjects in each group was required. Allowing for a drop-out rate of 25% over 30 months, a total of 300 subjects (100 in each group) were needed.

Arms:
arm 1: instructions on oral hygiene (OHI) tailored to the individual's condition will be given, and a tube of toothpaste containing 1,000 ppm fluoride (the most popular type of adult toothpaste in the Hong Kong market) will be provided. The OHI and provision of toothpaste will be repeated at 6-month intervals. In addition, distilled water as placebo with a bitter flavor added (to mimic the bitter metallic taste of SDF) will be painted onto all exposed tooth root surfaces using a small disposable brush. This procedure will be repeated after 12 and 24 months. arm 2: the subjects will receive the same intervention as those provided to subjects in the control group except that a 38% SDF solution (Saforide, Toyo Seiyaku Kasei Co. Ltd, Osaka, Japan) instead of the placebo solution will be painted onto the exposed tooth root surfaces. This treatment will be repeated after 12 and 24 months. arm 3: the subjects will receive the same treatment as those provided to subjects in the control group except that a 38% SDF solution instead of the placebo solution will be painted onto the exposed tooth root surfaces and followed by painting of a saturated potassium iodide solution. This treatment will be repeated after 12 and 24 months.

Interventions: intervention 1: silver diammine fluoride intervention 2: Water as placebo intervention 3: saturated potassium iodide solution
Intervention descriptions: intervention 1: topical application of the SDF solution onto tooth root surfaces intervention 2: topical application of water as a placebo in the control arm intervention 3: topical application of SDF solution followed by KI solution onto tooth root surfaces

Protocol document: