Repairing bark damage from voles/rabbits
Cass County North Dakota
There are multiple ways to help a tree repair itself. Most important is to prevent further damage. Sometimes this involves putting up a fence or some other obstruction to keep away rabbits/voles/mice or even lawn mowers and string trimmers. Sapsuckers (birds) can also cause damage, though usually that's higher up on the stem. In general, keep the tree otherwise healthy by preventing drought stress, insects, diseases or other pest problems.
Sometimes a tree will send up sprouts (suckers) in response to a wound. These sprouts will also help in the repair process by providing sugar (produced in photosynthesis) to the wounded area or to the roots so that they can continue to grow. Depending on the rate of wound closure, you may want to keep these sprouts for 2-3 years before removing them.
Regarding wound dressings, I have yet to see any scientific evidence of their increasing the rate of wound closure. And there is very, very limited evidence about the ability of these products to prevent future pest problems. Some products can even harm trees.
I hope this answers your question. Best wishes with your tree.