Dental Education Lecture: How does a Tooth Crack?
In last lecture we discuss crack happens most often after we are over thirty. We like to chew something hard. We chew on one side (overwork, wear and tear). This lecture gives you an example how a tooth cracks.
Mr. Li is in his forties. He loves to eat nuts. For a while, he avoids chewing on the right side, because the filling (F in Fig.1) of the tooth no.2 is chipped (arrowhead) and food gets between the teeth 2 and 3. So he uses his left teeth for chewing. Suddenly he has severe toothache. It is difficult to sleep. Exam shows that the troublesome tooth is in the lower left of his mouth, the tooth #19 (Fig.2).
Further exam shows that the tooth #19 has a crack line around a cusp (Fig.3 white arrowhead). Fig.4 red arrowheads delineate the crack line on the surface. We suspect that the crack extends deep into the nerve and causes nerve infection and pain. We have to do root canal. When we make a hole in the middle of the tooth for root canal, the crack line on the surface of the tooth (red arrowhead in Fig.5) takes a turn (black arrowhead) and goes into the middle of the tooth (blue arrowhead). Fortunately the crack does not extend into the root. We are still able to save the tooth after finishing root canal (Fig.6: arrowheads) and making a crown to hold the tooth together.
The lesson tells us that we need to avoid chewing on one side. If we have problems chewing on one side, we should fix them as soon as possible so that we can chew both sides. Crack tooth can be prevented or reduced.
Xin Wei, DDS, PhD, MS 1st edition 12/09/2010, last revision 12/09/2010