If your dog has killed another animal once, it’s a potential danger the rest of it’s life to all living things. Taking precautions to ensure it doesn’t lethally harm another being doesn’t mean it has a low quality life or bites all the time. Their dog is happy, healthy and extremely well trained now. Missing four teeth does not equal miserable to me. In a less responsible owners hands, the dog would of been euthanized and not given a chance to live the life it deserves, just because it was doing what it was breed to do for centuries.