Expert: Frederick R. Liewehr DDS, MS, FICD - 7/11/2005

Question
My dentist recently prepared a cracked molar for a temporary crown, and said after he had chiseled it down that the decay was all gone and I probably wouldn't need a root canal. After the temporary was on, I had constant throbbing pain in that tooth. I went in a week later and the dentist said he hit a nerve when preparing the tooth for the crown--and now I have to have a root canal on a tooth that didn't even need one! The pain isn't subsiding. How common is this to happen during crown-preparation, which seems fairly routine, and should I go ahead with the root canal now?  

Answer
Hi Caitlin,
    Some of the answer depends upon the shape your tooth's pulp, or "nerve" was in before the crown was prepared. You say it was cracked; cracks can run the full gamut from an inconsequential crack in the enamel to a tooth that is split in half. Usually, cracked teeth are sensitive to cold and to biting. This is because the dentin and perhaps the pulp itself are exposed when you bite (the crack opens up) and because cold causes fluid movement in the tubules in the dentin, which is exposed by the crack. When all this happens, the pulp becomes inflamed, and is very close to a toothache already.
     So, with a pulp that was about to give you a toothache because the pulp was inflamed, you had a crown prepared. The crown is necessary to prevent the crack from getting worse when you bite. Unfortunately, preparing a crown is yet another insult to the pulp, and guess what? It becomes even more inflamed, and whammo - a toothache. The dentist didn't even have to touch it, the drilling itself caused the increased inflammation.
    Sometimes the pulp can recover from even that much insult, but rarely. The fact that you have long-lasting spontaneous pain tells us that yours is not going to get better. Even if it did, it would be a mistake not to do the root canal before you place the crown, because it will undoubtedly eventually give you another toothache, and then the dentist will have to cut a hole in your nice crown to do the root canal. Better to have it done now. I just personally had exactly the same thing done - cracked tooth, root canal, crown. Happens all the time.
    So, you are on the right track. Good luck!

Dr. Liewehr