Cavity, Filling and Nerve
Cavity is very common. To fix it, we need a filling. When the cavity is big and deep, the doctor may poke into the nerve inside the tooth while placing the filling, causing more severe pain. The doctor may be in severe trouble.
Mr. Zhang has a large cavity (Fig.1: *) in his lower 2nd molar (2). The cavity may be due to the presence of the 3rd molar (3, wisdom tooth) before. His 1st molar (1) is also gone. So Mr. Zhang badly wants to save the 2nd molar.
The cavity (Fig.2 black arrowheads) is pretty close to the nerve (white arrowheads). After removing cavity, no nerve is encountered. So a filling is placed (Fig.3: F). But the filling is quite close to the nerve (*). Mr. Zhang luckily feels great after filling.
Three-dimensional CT is taken for the purpose of placing an implant for 1st molar. So we have an opportunity to take a look how close the filling is to the nerve. Let us make a thin section through the tooth as indicated by dashed line in Fig.3. The transverse section shows that the filling (Fig.4: F) is indeed very close to the nerve (*). Let us make another section as shown in Fig.4 pink line.
The new section (Fig. 5, the same orientation as Fig.1-3) clearly shows that the filling (F) is 0.31 mm from the nerve (N). You may see how lucky the patient and the doctor are. If the doctor happened to drill a little bit more, the nerve would be irritated. Mr. Zhang would have severe pain. He would not be a happy guy.
Xin Wei, DDS, PhD, MS 1st edition 12/17/2011, last revision 04/18/2012