I have a rescue dog who was kept chained and enclosed for the first 18 months of her life. When we first got her and took her to our vet we thought that she too had had her teeth filed down as they were short and squared off. Our vet in PA, having had a lot of dealings with puppy mill dogs had seen many instances of this and was quite sure that her teeth were worn down as a result of frantic chewing at the wires of her enclosure during her early containment. Erin is extremely thunderphobic and we know she came from a bad environment and no doubt had to endure many a storm with nowhere to escape from them so this seems quite a likely reason for her teeth being in the condition they are, particularly as she did not know how to play with any toys when she came to us, so they were not the culprit!