A current review of the evidence for using silver diamine fluoride (SDF) in managing caries reports there is a lack of controlled human data. The FDA has reached a similar conclusion and has required controlled human studies to prove SDF works to treat existing decay.
Controlled studies to show an intervention prevents caries are tricky, expensive and take forever. Prevora, for example, has completed 4 such studies in patients ranging from adolescents to old age, and in patients with medium to very high risk. To show a significant reduction in caries in the treated group versus placebo, has required the following design in the Prevora controlled studies: an observation period of at least a year, carefully chosen and trained dental examiners, incentives to keep study participants engaged, and recruiting participants who are almost certainly going to experience the disease during the study.
So, good luck to SDF in showing evidence similar to Prevora.
And if and when it does, SDF is a compatible approach to Prevora. SDF might arrest existing lesions, not newly emerging ones like Prevora. And SDF treats only existing caries not chronic oral inflammation too, like Prevora.