In vitro Rehardening and Staining Effects of Silver Diamine Fluoride with and without Mucin on Early Enamel Caries Lesions

Abstract

PURPOSE: Investigating the rehardening ability of SDF and its individual components, silver and fluoride ions, on early enamel caries lesions using artificial saliva with and without mucin. METHODS: Early caries lesions were created in human permanent enamel specimens. The specimens (n=36 per group) were then treated with a single application of: SDF (38%), SDF followed by application of potassium iodide (SDF+KI), potassium fluoride (KF; fluoride control, 44,800 ppm F), silver nitrate (AgNO3; silver control, 253,900 ppm Ag), or deionized water (DIW). Immediately, the specimens were subjected to four days of continuous remineralization with or without mucin (n=18 per subgroup). Changes in Vickers surface microhardness from lesion baseline (∆VHN) were calculated. Data were analyzed using two-way (intervention vs. rehardening models) ANOVA. RESULTS: In both rehardening models (with or without mucin), SDF (∆VHN data; mean ± standard deviation; with/without mucin: 26±19/3±11) was significantly less effective in rehardening promotion than SDF+KI (37±12/39±16) and KF (40±17/41±29; p≤0.0332). Compared to AgNO3 (9±9/18±15) and DIW (3±7/12±9), SDF was more effective in the presence of mucin (p≤0.001) but not in its absence (similar to DIW – p=0.11; less effective vs. AgNO3 – p=0.0061). The presence of mucin significantly increased the rehardening ability of SDF (p<0.0001). However, mucin did not affect the extent of rehardening in the other groups (p≥0.082). SDF+KI and KF were superior in their ability in rehardening promotion than AgNO3 and DIW in both rehardening models (p<0.0001). In both rehardening models, ΔL* values from baseline to post-rehardening show that applying KI after SDF significantly lessened the dark staining caused by SDF (p<0.0001). Under the present in vitro conditions, SDF does not appear to enhance surface rehardening of early enamel caries lesions. The co-presence of mucin during rehardening enhanced the efficacy of SDF which warrants further investigation. CLINICAL SIGNIFICANCE: SDF+KI may be a viable option in rehadening of early enamel caries lesions.