Preventing root caries with SDF in fluoridated and non-fluoridated areas

Abstract

Objectives: To describe the effectiveness of annual application of silver diammine fluoride (SDF) solution in preventing root caries in community-dwelling elders living in fluoridated and non-fluoridated areas. Methods: This was a 2-site randomized controlled trial conducted in Hong Kong (HK), an optimally water-fluoridated area, and in Guangzhou (GZ), non-fluoridated with a water fluoride concentration <0.2 ppm. Community-dwelling elders who were generally healthy and had at least 5 teeth with exposed root surfaces (not indicated for extraction) were recruited and randomly allocated into 2 groups: test – annual application of 38% SDF solution, and placebo control – annual application of tonic water. Individualized oral hygiene instructions and a toothpaste with 1000 ppm fluoride was provided to all subjects. Status of the tooth root surfaces were examined by calibrated examiners at baseline and thereafter every 6 months. Results: A total of 533 elders (mean age = 68.6) were recruited at baseline, 260 in HK and 273 in GZ. After 24 months, 413 (77.5%) of these elders were examined, 208 in HK and 205 in GZ. The mean numbers of new root surface caries in the four groups were: 0.52±0.86 in GZ control, 0.46±0.82 in HK control, 0.32±0.68 in HK test, and 0.18±0.48 in GZ test (ANOVA, p=0.004). The pooled mean 24-month root caries increments in the subjects receiving SDF application and those receiving placebo were 0.25 and 0.49, respectively (t-test, p=0.001), giving a prevented fraction of 49%. Other studied possible confounding factors such as denture wearing and full-mouth plaque score did not have a statistically significant impact on the development of new root caries (ANCOVA, p>0.05), except baseline DMFT score (p<0.001). Conclusions: Based on the 24-month results, it is concluded that annual topical application of 38% SDF solution can prevent root caries in community-dwelling elders in both water-fluoridated and non-fluoridated areas.