(2) Preparing the canal. Once the diagnosis is made, local anesthesia may
be administered by the dental officer. The rubber dam is applied and the area of the
rubber dam around the affected tooth is swabbed with an iodophor or alcohol disinfectant.
The dental officer uses a high-speed handpiece to create an occlusal or lingual opening
into the pulp chamber of the tooth. The slow-speed handpiece may be used to refine the
shape and size of the opening. Next, a barbed broach may be used to remove the pulp
tissue. At this point, a small file fitted with a rubber stop (figure 4-14) is placed in the root
canal and the dental specialist takes a periapical radiograph of the tooth containing the
stoppered file. This is referred to as the trial-file radiograph and is used to determine the
correct working length of the files used. Once the working length is determined by the
dental officer, all files used will be measured with the endodontic ruler and stoppered at
the correct working length. The working length, expressed in millimeters, should be
recorded in the patient's treatment record. Using reamers and files of increasing size
stoppered to the correct working length, the root canal can be gradually shaped and
enlarged. During the filing, the canal is irrigated to provide lubrication and a flushing
action on the debris. Sodium hypochlorite (5 percent solution) is usually the irrigant used,
and is administered with a large plastic syringe. When filing is completed, small paper
points are used to dry the root canal.
Figure 4-14. Endodontic ruler and file with rubber stop.
(3) Filling and sealing the canal. When the dental officer has determined that
the root canal is sufficiently enlarged, he will select and trial-fit a gutta-percha point or
silver point of the same size as the last file used. Once the point passes the trial fit, it is
ready to be cemented. The dental specialist mixes the root canal cement or prepares a
mix of zinc oxide and eugenol that can be drawn up from the mixing slab about 1 inch
without separating. The point is coated with the cement and seated into place.
Depending on the technique, a plugger or a spreader, or both, is used to condense the
gutta-percha in the root canal. When the root canal has been filled satisfactorily, a thick
mix of zinc oxide and eugenol or zinc phosphate cement is made and plugged into the
access area to completely seal the canal. Completion of the endodontic treatment may
not be accomplished in a single appointment. Therefore, medicament may be placed
inside the pulp chamber or canals in a cotton pellet or paper point. The access opening is
then sealed with an interim restorative material such as IRM.