Dental Education Lecture: Root Canal Therapy Part II
In last lecture, we compare pulpotomy and root canal. If infection is limited to the most coronal (upper) portion of the pulp (red in Fig.1), removal of the infected and some of uninfected (green) pulpal tissue (pulpotomy) most likely cures the infection (Fig.2). When infection is beyond the coronal pulp (Fig.3), we need to perform root canal therapy. That is to remove all of pulpal tissue, followed by filling the empty canals (1, Fig.4), build-up (2) and crown (3).
If pulpotomy is done for severely affected tooth (like the one in Fig.3), the infection persists on the right side of Fig.5. The once partially infected pulp in the left root gradually degenerates, i.e., becomes unhealthy, and finally dies (pink, Fig.5). The latter may cause a mild form of root tip infection (small red circle on the left, Fig.5). During nerve degeneration, the root canal space becomes narrow (compared the size of left root canal in Fig.5 vs. that in Fig.3). If root canal therapy is needed for the narrow canal, it is difficult to do so.
To assure success, we need to perform root canal therapy for the adult tooth with pulpal infection. Root canal therapy involves several steps: remove cavity (Fig.6), remove coronal pulp (Fig.7), remove radical pulp (Fig.8), enlarge root canal diameter (Fig.9) to remove residual infected root pulp attached to wall of root canal (as shown in Fig.8), rinse canal with disinfectant (Fig.10), and finally pack canal hermetically tight (brown, Fig.11) to prevent re-infection. Every single step in root canal therapy is critical, each step making next step easy and smooth, laying foundation for final treatment success. For example, enlarging the canal is painstaking on the part of the doctor. He or she uses several small to large files for shaping. Between changing files, the canal needs to be rinsed to rid of shaving and bacteria. Each time, a file cannot pass out of the root tip (arrowhead, Fig.9) to prevent damaging to outside tissue. The file cannot afford to be too short of the root tip, leaving dead tissue and bacteria untouched. If the canal is too narrow or too curvy, difficulty is expected. In all, pulpotomy is an incomplete nerve treatment leaving potential problems behind. We should conduct root canal therapy for an adult tooth in the first place. It may be alright to do pulpotomy for a baby tooth, since it is going to fall out in a short period of time.
Xin Wei, DDS, PhD, MS 1st edition 01/28/2009, last revision 02/17/2009