If this happens don’t panic.
Think about it; if the bone was able to fit over the jaw and behind the canines than it is large enough to come back off.
Try this method before rushing to the vet:
With dog standing place your hand on the dogs throat grabbing the skin and pull down toward the chest. At the same time pull the bone from under the jaw up toward the ceiling. It will usually slip right over the canines and off the jaw.o
To prevent this from happening be sure your marrow bones are long enough – at least 6″ or more and that the center h0le is not too large.