Inclusion Criteria:
* Child:
* Male or female, between 12-71 months of age at baseline, up to the day the child turns 6 years old.
* Must allow examination of the oral cavity and application of treatment by the examiners at baseline.
* Must have S-ECC \[defined as: In children younger than age 3, any sign (non-cavitated or cavitated lesion) of caries in any tooth surface (i.e., most common for this age group will be on erupted smooth surfaces). From ages 3 through 5, ≥1 dmfs in maxillary anterior teeth; or a dmfs score of ≥4 (age 3), ≥5 (age 4), or ≥6 (age 5) constitutes S-ECC. Note: The "d" component of the dmfs index is defined as including cavitated and non-cavitated lesions, thus ICDAS\>1\].
* Have at least one SDF-target tooth with
* Soft cavitated caries lesions extending into dentin \[ICDAS 5 or 6\];
* Cavitated lesion(s) that allow for direct hardness assessment and application of SDF (microbrush applicator must fit the cavity and be able to access all exposed dentin).
* Parent/Legal Guardian:
* Provide written informed consent for the child and her/himself prior to participation.
* Must be at least 18 years old, or an emancipated minor who provides documentation of emancipation.
* Must be willing and able to participate in trial activities.
Exclusion Criteria:
* Child:
* Hereditary generalized developmental dental defects such as Amelogenesis Imperfecta and Dentinogenesis Imperfecta.
* Known allergy/sensitivity to silver or other heavy metal ions.
* Presence of any gingival or peri-oral ulceration, abscess or stomatitis.
* Participating in the foster care system at trial initiation.
* Toothache pain at baseline (based on Dental Discomfort Questionnaire score of 1 or higher).
* Note: If toothache pain occurs after baseline, the child remains eligible to continue in the trial as long as he/she has at least one trial tooth that meets tooth inclusion/exclusion criteria.
* Demonstrated inability to comply with trial protocol requirements (determination is at the Clinical Site Investigator's discretion).
* Rickets.
* Osteopenia or osteoporosis (e.g., Osteogenesis Imperfecta, Ehlers-Danlos Syndrome, Marfan Syndrome, etc.).
* Chronic diseases such as chronic kidney disease, leukemia, lymphoma, rheumatic disorders, etc.
* Metabolic bone disease (e.g., Galactosemia, Glycogen Storage Disease Type 1, etc.).
* Chronic glucocorticoid, anticonvulsants, chemotherapy, bisphosphonate administration.
* Hypothyroidism, hyperparathyroidism, impaired glucose tolerance, hypocalcemia or hypophosphatemia.
* Tooth:
* Pain due to caries (based on DDQ score of 1 or higher).
* Note: If toothache pain occurs after baseline, the tooth is removed from the study.
* Pulpal exposure, or signs of pulpal infection (abscess, fistula, swelling).
* Mobility not associated with expected exfoliation patterns.
* Parent/Legal Guardian:
* Demonstrated inability to comply with trial protocol requirements (determination is at the Clinical Site Investigator's discretion).
* Inability to read and comprehend the consent document or trial questionnaires in the translated languages available.
