Advantage Arrest treated sites will arrest and partially remineralize (although not enough to show up radiographically).  This site will now be impregnated with silver minerals and fluoride.  The silver, although chemically bound to the tooth, is not part of the natural tooth structure and will gradually release into the mouth.  This takes years to happen (2 or 3), but if enough leaches out of the tooth, it could soften back up.  This leaching effect is why one Advantage Arrest treated site in a mouth will help protect all the other teeth. If the patient improves their care and lowers their caries risk, it’s possible that as silver leaches out, the lesion will remineralize naturally and stay arrested.  This is dependent upon the patient and their home care.  Reapplying Advantage Arrest in either case will ensure it stays arrested. If you cover over an Advantage Arrest treated surface, it will hold the Advantage Arrest in place and not need re applied.