Why can a tooth become sensitive after a filling or a crown preparation?
Teeth are made up of four different types of tissue: pulp, dentin, enamel, and cementum. The inner portion of a tooth is called the pulp. The pulp is made up of nerves and blood vessels. The next layer of the tooth is called the dentin which is comprised of millions of tiny tubules, filled with fluid, that conduct impulses or sensations to the pulp. Dentin surrounds the pulp. A hard yellow substance, it makes up most of the tooth and is as hard as bone. It’s the dentin that gives teeth their yellowish tint. Enamel, the hardest tissue in the body, covers the dentin and forms the outermost layer of the crown. It enables the tooth to withstand the pressure of chewing and protects it from harmful bacteria and changes in temperature from hot and cold foods. Both the dentin and pulp extend into the root. A bony layer of cementum covers the outside of the root, under the gum line, and holds the tooth in place within the jawbone. Cementum is also as hard as bone.
I contend that God played a cruel joke on animals when He designed teeth. As I see it, one of the only purposes of the pulp is to allow the tooth to develop. Without the dental pulp, there would be no tooth. Once developed, the pulp just tends to wreak havoc. In addition, sensation, in particular of pain, is a protective function of the pulp, and can help prevent people from doing further damage to the teeth.
There are several reasons a tooth may become sensitive after a filling or a crown:
1. A High Bite: The most common reason is a bite that might be slightly off or “high”. If a patient comes to my office with a recently filled tooth and the tooth is hurting, the first thing I do is check the bite. We use carbon ribbon and ask the patient to “tap” their teeth together and to slide from side to side. If I notice that the ribbon is marking the offending tooth more than the other teeth, I’ll adjust the filling or crown, thus relieving the bite. Often this is all that is necessary to make the tooth comfortable.
2. Reversible Pulpitis: Imagine you had a hole drilled in a bone….you would expect it to be sore for several days, especially if it is in function as a tooth is when you are chewing. A dental drill causes vibration and heat, (even though we do use water when drilling) and the pulp gets irritated. Because the pulp is in a confined space (in the middle of your tooth) it really doesn’t have anywhere to expand and thus it causes the tooth to feel sore. Most of the time the pulp will settle down within a couple of days or weeks, much like a bump or a bruise does.
3. Irreversible Pulpitis: Oftentimes, when there is a deep cavity, one that is near the pulp, the pulp becomes irritated so much that it starts to necrose or die. With a deep cavity, microscopic bacteria may already be offending the pulp, but as a dentist, we can’t always determine this. We oftentimes do our best to insulate the pulp with a base under the filling. However, once a pulp starts to die, the only treatment we can do to save the tooth is a root canal therapy (endodontic treatment). A root canal therapy removes the nerve and places an inert material called gutta percha in the root canal system. You may realize your tooth may need a root canal therapy if it causes intense or throbbing pain, it wakes you up during your sleep, or you have an earache (lower molar).
In short, teeth can be a challenge to both a patient and a dentist. I guess that’s why God created dentists…..and root canal specialists.