WHY CRACKS ON A LOWER MOLAR INDICATE A TOOTH SHOULD BE CROWNED
Sometimes a dentist recommends a crown for a tooth such as a lower molar, but the tooth doesn’t hurt or feel odd. Is the dentist wrong? Not likely.
The further one chews towards the back of the mouth, the more force is generated on the teeth. On the back of the lower molars, a crack can develop. Without treatment the crack gets deeper and deeper. There is a point where it gets so deep that it gets into the dentin and can become sensitive to chewing. If the crack is big enough it can get into the nerve, requiring root canal treatment to save the tooth. If the crack gets even bigger, the crack goes down the root and may require that the tooth be extracted. That is a condition that we are trying to avoid.
A tooth that has had a root canal and has a crack on it needs a crown as soon as possible. I have seen patients wait on getting the crown only to crack the tooth further down the root, past the point where it can be restored. It’s a disappointing when a patient spends the time and money to get a a root canal, only to see the tooth become no longer restorable.
On rare occasion where there is a small crack on the molar I will try to restore the tooth with a small filling, with the hope this will provide enough protection for the chewing forces that can spread the crack apart. If the crack is too big, then something more substantial, like a full coverage crown restoration or an onlay to protect the chewing cusps of the tooth on either side of the crack is indicated.
One situation that I have seen is when the root canal specialist starts to perform the root canal he can see a crack that goes inside the canal. This is another case where the root canal treatment will not work and the tooth needs to be extracted. Technology is improving with the CT scans used in dentistry, and there is a better chance of picking up these fractures before any treatment is even started.
There is a dilemma for the dentist. I personally do not like to put a crown
on a tooth where there is nothing but a crack on the back of it. However, being too conservative can be a problem. If a patient exhibits a lot of wear on their teeth, then having a stronger restoration like a crown, covering more surface area, is the choice offering more protection from fracture.