PROJECT SUMMARY / ABSTRACT Dental caries is a preventable disease, however, it still affects large numbers of people globally and in the US. The Global Burden of Disease 2017 study showed an estimated 2.3 billion people had dental caries of permanent teeth, and of all evaluated conditions, oral disorders ranked first in age-standardized prevalence in males and females. Data from the US National Health and Nutrition Examination Survey 2011-2016 cycle found that 1 in 4 adults ages 20 to 64 years have untreated tooth decay. Approximately equal numbers of males (28.0%) and females (24.3%) had untreated caries. Variation was observed according to race and ethnicity and higher rates were observed for non-Hispanic blacks (40.2%) and Mexican American (37.1%) compared to non-Hispanic whites (22.2%). Additional variation was noted according to poverty status, with 45.3% of adults with income less than 100% federal poverty level having untreated tooth decay, compared to only 17.7% of individuals with greater than 200% federal poverty level status. Furthermore, according to a survey conducted by the American Dental Association in 2015, 59% of adults indicated that they forgo dental care due to cost, 22% because they are afraid of the dentist and 19% because they cannot find a convenient location or appointment time. Taken together, these statistics underscore the importance of dental caries treatment that is easy to access, affordable and effective. Silver diamine fluoride (SDF) has been used in many parts of the world to arrest dental caries, however, multiple systematic reviews using data from randomized controlled trials have concluded there is evidence to support carious lesion arrest in primary teeth in children, but there is insufficient evidence to draw conclusion for effectiveness on permanent teeth in children or on coronal surfaces of teeth in adults. Given that large-scale prospective studies on adult caries outcomes are costly and lengthy, and that dental caries is a multi-factorial disease process, it is important for studies to collect data on key factors such as medical comorbidities, medication use, and access to preventive dental services. Our proposed use of existing data thus represents a highly efficient approach to conducting robust analyses on the effectiveness of SDF to arrest carious lesions in adults and prevent the need for more invasive treatment. Thus, our primary aim is to determine whether teeth treated with SDF to arrest a carious lesion required subsequent caries-related extraction, root canal therapy or direct/indirect restoration during the 1-5 year follow-up period. Our secondary aim is to determine whether 2 or more applications of SDF are more effective than 1 application at preventing subsequent caries-related extraction, root canal therapy or direct/indirect restorations during the 1-5 year follow-up period.