When an incisor becomes devitalised (loses its blood and nerve supply), it can become discoloured, weaken, and in some cases become infected. This can be the result of trauma, developmental issues, or previous dental disease.
After the tooth dies, there is an open channel through the pulp cavity to the bone underneath, and bacteria can travel along this canal and cause a tooth root infection. Sometimes pus escapes through a tiny pimple on the gum called a draining sinus tract.
Our clinic horse, Panda, had a devitalised incisor with a draining sinus tract. X-rays showed a widened pulp cavity, and blunt root. With sedation, and local anaesthetic nerve blocks to make his tooth numb, we extracted the tooth.
We're hoping he will feel much happier once it all heals up!