Title: Cariostatic effect of Riva star: Silver diammine fluoride without the black staining
Recently, Silver Diammine Fluoride (SDF) has drawn considerable attention from dental researchers due to its outstanding effectiveness in preventing and arresting dental caries, and its non-invasive method of application. As SDF combines the remineralizing effect of fluoride with the antibacterial effect of silver, it is more effective in caries control than other minimally invasive treatments such as fluoride varnish. However, a major disadvantage of using SDF is the black staining of the treated lesion. Riva Star (SDI Ltd; Asutralia), a commercial SDF product, included saturated solution of potassium iodide (SSKI) to prevent the discoloration by formation of creamy-white AgI. This SDF/KI treatment has been reported to possess high anti-bacterial property. However, its inhibitory efficacy on human enamel demineralization is still unclear. In our in vitro study, enamel samples were topically treated with SSKI (1 g/mL), SDF (3.16 M) or Riva Star (SDF/KI) using micro-brush, after being demineralized in pH 4.0 buffered acetic acid for 4 h. Next, the treated sample was put back into the acid for further 4 h demineralization. Throughout the 8 h demineralization study, calcium, silver and fluoride ion selective electrodes (ISEs) were used to monitor the concentrations (activities) of ions, and the rates of Ca2+ release before and after treatment were used to obtain the percentages of the reduction in the rates of enamel calcium loss (PRCLenamel). Later, these samples underwent the Vickers micro-hardness test (HV), and the inspection of scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX). The mean PRCLenamel are 10.2+5.8 %, 61.1+4.5 % and 61.7+3.8 %, for SSKI, SDF and Riva Star treated groups, respectively. No Ag+ release was observed in SSKI and Riva Star treated groups. The mean reductions in HV of enamels are 108.2+12.9, 64.1+7.3, and 58.1+10.7, for SSKI, SDF and Riva Star treated groups, respectively. No black staining was observed on the Riva Star treated sample. In conclusion, Riva Star can inhibit enamel demineralization without black staining the lesion.