crown jewels: uncomplicated crown fractures
As we discussed in the last post, any fractured tooth with direct pulp (nerve) exposure is a medical problem. Treatment options are root canal therapy or extraction. However, the pulp does not need to be directly exposed for the tooth to be a problem.
Teeth are roughly broken up into three layers: enamel, dentin, and pulp. The innermost layer is the endodontic system (root canal or pulp). It contains the nerves, blood vessels, and connective tissue which supply and nourish the tooth during life.
The outer layer of the tooth crown is enamel. It is virtually all calcium and phosphorus and is the hardest substance in the body. Enamel has no nervous or circulatory system. It is very thin (less than 1-mm in veterinary patients). Once eruption has occurred, enamel cannot be replaced or repaired.
The central layer, which is the vast majority of the tooth structure in mature patients, is dentin. Dentin has roughly the same mineral content as bone. Dentin is a somewhat living structure which has a nervous supply and can respond to stresses. Running at right angles to the root canal all the way around the tooth from the root canal out to the enamel are dentinal tubules. Each one of these dentinal tubules contains an odontoblastic process, which is basically a nervous supply; however they are only sensory and can only report changes as pain. There are approximately 50,000 dentinal tubules per mm2. Therefore, a 1 cm area of enamel loss will expose 3-4 million odontoblasts! This is twice as many nerve endings as we have, and therefore our pets teeth are twice as sensitive as ours are.
Uncomplicated crown fractures occur when the tooth is fractured, an area of enamel is lost and the underlying tooth structure (called dentin) is exposed, but the root canal is not directly exposed. This is very common, particularly in large breed dogs.
These fractures result in direct dentinal exposure, and exposed dentinal tubules create significant pain (or sensitivity) for the patient. In addition, some of these teeth die due to the traumatic incident, and/or associated inflammation. Therefore, it is recommended that these teeth be radiographed to ensure vitality. Finally, the roughened surface increases plaque attachment leading to an increase in periodontal disease. For all these reasons, we recommend treating these fractures.
First, the veterinarian will place the pet under anesthesia to perform a complete exam. The area is carefully evaluated to determine pulp exposure or other extensive damage. Next, they will use a dental explorer to definitively rule out pulp exposure. Finally, a dental radiograph should be exposed to ensure that the tooth is still alive.
If the dental radiographs are normal, a bonded sealant, or filling, should be performed on the tooth. This entails smoothing out the tooth and applying a clear resin “filling” on the exposed dentin. This will remove sensitivity, block off the pathway for infection, and smooth out the tooth to retard periodontal infection. Recheck dental radiographs are recommended in 9-12 months to ensure continued vitality.
If there is radiographic evidence of endodontic (root canal) disease, root canal therapy or extraction will be needed. If your pet shows any signs of oral pain, including changes in eating behavior, bad breath or excessive drooling, contact your veterinarian right away for an appointment.