Not yet investigated
What we have so far
The tin salt does something the sodium salt has no mechanism for: it is antibacterial, and it plugs dentine tubules. Its old drawback was staining teeth brown.
This star is on the map because the show intends to take the question apart properly — the trials, how it is actually tested, whether the thing sold is the thing studied. That work is not done yet, and nothing here should be read as a conclusion. When the investigation is published it will appear on this page.