Not only is this painful, but it always leads to an abscessed tooth. Again, the problem is that most animals mask the pain until so much damage is done that nothing can be done to salvage the tooth.
Early treatment is the best answer.
Waiting until the tooth turns black is the wrong answer. The indication for root canal therapy is pulpal disease. Trauma Caries End stage periodontal disease. Pulpal hemorrhage, traumatic exposure of the pulp and to a limited extent caries can be dealt with by conventional endodontic therapy. Stage 5 and 6 periodontal disease combined with endodontic disease is much more difficult for the veterinarian to deal with.