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June 2005Strategies for the 3 Canal Mandibular Premolar

Manbular premolars can present with some of the most difficult and unusual canal anatomy.  Not only can that have apical bi and trifidities, they can also present with multiple orifices that join at the apex.  This mandibular 2nd premolar I present this month had anatomy similar to that of a case that I showed in the August 2002 Case of the Month.

The referrals initial preoperative film showed the classic “fast break” where the coronal aspect of the canal is of a large diameter and then quickly narrows and splits. This configuration is not only present in the 2nd premolar; it can also be seen in the first premolar as well. (See red arrows).  Unlike in the earlier case, the apical width seemed larger and I was unsure prior to commencing treatment whether multiple separate POEs were present. There was only one way to find out; make an access and place some files.


Initially, I decided to place two files into the orifice to see if I could determine whether I had a common apex. The first image (Fig.3) showed what appeared to be a single canal. I knew this was an error and caused by overlap of the canals. We then shifted the shot mesially (Fig. 4) and the true configuration of the canal system began to reveal itself.  The more mesial of the two files joined with the distal file, close to the apex. This was confirmed by tactile sensation, use of an apex locator and by the fact that it was slightly short of the distal canal working length when the smaller could no longer easily be advanced. Closer examination of the image ( Fig.4) clearly showed that a third, more mesial canal was quite visible. (yellow arrows)

Since at least 2 of the canals joined, I chose to prepare the easier canals (and straighter of the two previously discovered canals) first. I then placed a gutta percha cone into this prepared “middle” canal and placed two files in the adjacent mesial and distal canals. All three joined at the apex, as evidenced by two file puncture marks made in the most apical portion of the gutta percha cone.  (Fig.5)

Two more images were taken of the cones fits ( with sealer), revealing similar results. Cones were placed but unfortunately, due to the limitations of the access size I was only able to place 2 cones into the access initially. Since all canals joined, I wasn’t so concerned about not placing a cone in the 3rd canal. I could could fill it with the Obtura once the merged apical portions had been compacted.

As I mentioned in the Aug 2002 case, anatomical variations must be constantly kept in mind when considering endodontic treatment of mandibular premolars. It is important to try to obtain every possible bit of information not only prior to starting the case but also as you proceed with treatment. The results of instrument insertions and placement, markings on gutta percha cones, effects of suctioning an adjacent irrigated canal (i.e./ lowering of  irrigation level indicating the canals join) all are important bits of information that help determine how best to treat the case. Knowing the position and location of joined canals, common foramina and unusual anatomy will increase accuracy of preparation, reduce the likelihood of instrument breakage and allow you to select the best method of canal obturation.