The combination of two different fluoride mechanisms, .31% APF (uptake properties) and 1.64% Stannous (barrier & cariostatic properties) makes logical sense but these two-part rinses have never been clinically proven. Their main drawback is treatment time and the reduced safety involved with the increased potential for accidental ingestion. One minute would be an eternity for a child to rinse without swallowing. Their main use is limited to older children or adults in active orthodontic treatment.