This article is from the Dog Behavior FAQ, posted to rec.pets.dogs newsgroup. Maintained by Cindy Tittle Moore with numerous contributions by others.
There is a "No-Bark Muzzle" that is designed to prevent dogs from barking. Many dogs very rapidly learn not to bark when the muzzle is put on them each time they start barking. It is not binding or confining and does not put the dog through surgery. In general, though dogs should not be left alone with muzzles on, unless it allows them to drink.
 
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