If your dog doesn’t finish a dental chew within a couple of hours, it’s best to throw it away. As your dog chews the treat, it picks up moisture from his saliva. If the chew is then left out to dry, it can harden, which may cause your dog to break a tooth if you give it back to him later. You’re better off cutting or breaking a chew in half before you give it to your dog if you want to save a portion for later use.