Background: Silver Diamine Fluoride (SDF) has garnered much interest because of its ability to reduce and arrest dental caries, excellent antibacterial action, and effectiveness as an efficient alternative to restorative materials, when restoration is not an option. Alteration in dental plaque ecology serves as a major factor in caries development. Plaque pH is a direct reflection of the plaque ecology. But there is no scientific literature available about the effect of SDF on plaque pH. Aim -To evaluate the effect of SDF on plaque pH.