Matrix Metalloproteinases Inhibitory Effects of Silver Diamine Fluoride: Influence of Time and Potassium Iodide, In Vitro

BACKGROUND: Silver diamine fluoride (SDF) arrests caries, partly by inhibiting matrix metalloproteinases (MMPs). Potassium iodide (KI) is often applied after SDF to mitigate tooth darkening. AIM: This in vitro study evaluated the effects of application time and potassium iodide on SDF-mediated MMP inhibition, and assessed surface microhardness following SDF ± KI application. DESIGN: Seventy-two carious (ICDAS score 5 or 6) dentine blocks from 34 teeth were randomly assigned to one of four groups: baseline, SDF, SDF + KI and control. Total MMP activity was measured using a colorimetric assay. For enamel lesions, surface microhardness (VHN) was assessed on 20 enamel surfaces from 10 teeth (ICDAS 2). RESULTS: After 1 week, SDF significantly inhibited total MMP activity by 93% (p < 0.001). SDF + KI showed a lower, not statistically significant level of inhibition of 55.5% (p = 0.07). Surface microhardness of enamel caries lesions increased by 66.8% (p < 0.0001) with SDF and by 71.5% (p < 0.0001) with SDF + KI. No significant difference was observed between 1 and 3 min of SDF application. CONCLUSION: In this in vitro model, SDF demonstrated strong MMP inhibition, while SDF + KI showed lower numerical inhibition, suggesting that KI may attenuate the anti-MMP effect of SDF. SDF and SDF + KI produced similar increases in surface microhardness of non-cavitated enamel lesions.