The inhibitory effects of silver diamine fluorides on cysteine cathepsins

Abstract

Aim The expression of cysteine cathepsins in human carious dentine suggests that this enzyme contributes to the collagen degradation in caries progress. This study investigated whether silver diamine fluoride (SDF) inhibited the activity of cysteine cathepsins. Methods Three commercial SDF solutions with concentrations at 38%, 30% and 12% were studied. Two fluoride solutions with the same fluoride ion (F-) concentrations as the 38% and 12% SDF solutions, and 2 silver solutions with the same silver ion (Ag+) concentrations as the 38% and 12% SDF solutions were prepared. Five samples of each experimental solution were used to study their inhibitory effect on two cathepsins (B and K) using cathepsin assay kits. Positive control contained assay buffer and cathepsins dilution was used to calculate the percentage inhibition (difference between the mean readings of the test solution and control solution divided by that of the control group). Results The percentage inhibition of 38%, 30% and 12% SDF on cathepsin B were 92.0%, 91.5% and 90.3%, respectively (p < 0.001); on cathepsin K were 80.6%, 78.5% and 77.9%, respectively (p < 0.001). Ag+ exhibited the inhibitory effect against both cathepsin B and K with or without the presence of F- (p < 0.01). The solutions containing Ag+ have significantly higher inhibitory effect than the solutions containing F- only (p < 0.01). Conclusion According to this study, SDF solution at all 3 tested concentrations significantly inhibited the activity of cathepsin B and K. METHODS: An oral health survey was performed between 2011 and 2012 to select Dai five-year-old children using multi-stage stratified sampling in Yunnan. Their dental caries experience was measured using the 'dmft' index, and severe caries was assessed using the 'pa' index, which is modified from the 'pufa' index. Oral hygiene status was assessed using the visual plaque index (VPI). A questionnaire to study the children's socio-demographic background and oral health-related behaviours was completed by the children's parents. RESULTS: A total of 833 children were examined. Their caries prevalence was 89% and 49% of the children had carious tooth with pulp involvement. The mean (SD) dmft score was 7.0 (5.3). Higher dmft scores were found among children who were girls, were currently bottle-fed, took daily sweet snacks, had higher VPI scores, and had visited a dentist within the last year. CONCLUSIONS: The caries prevalence and experience of the five-year-old Dai children in Yunnan, China was high, and almost half had severe caries. The caries experience was associated with gender, snack habits, dental visit habits, and oral hygiene status.