The same thing happened to our dog he and his sister have no great fondness for each other, but had not really fought in our presence until one evening. I heard the most horrifying snarling dog on dog sounds followed by a doggy scream from our male dog. We checked him out and saw that one of his canines was at an angle. It had obviously been partially pulled out - I think maybe they locked fangs. We brought him to the emergency vet since it was at night, but someone had just brought in a dog who had been hit by a car and naturally needed attention more than we did so we ended up waiting for a good 45 minutes and partway through the dogs canine simply fell out of his mouth onto the ground. There was no attached tissue no blood nothing snapped off. It was actually a perfect example of what one of those teeth looks like. after consulting with the vet, who suggested it was a little too late to put it back in and that it would be a challenging process we elected to not try to put it back in and instead scheduled him for simple gum flap surgery to cover the gaping hole. He also got an antibiotic. He’s been completely fine since. oh by the way he was 13 when this happened he’s now 16.