Written by Scott Perkins, DDS Friday, 31 March 2006 19:00
In terms of performing a successful endodontic procedure, the challenges faced in creating consistently good access to the pulp chamber and eventually the root structure are staggering. They are as follows:
Visual Problems: Because second molars are farther back in the mouth and often angled distally, one simply cannot see into the pulp chamber in order to visualize the canal orifices. Even if there is visual access, it is difficult to angle the operatory light so that the pulp chamber is illuminated sufficiently.
Physical Problems: Assuming the visual problems can be overcome, there is not enough interarch distance between the maxillary second molar and it’s opposing tooth. The space is insufficient to get the files into the canals, especially the mesiobuccal canal.
Accuracy Problems: Which reference points do you commonly use to place your rubber stops against? A proximal marginal ridge? A cusp tip? Variable anatomic landmarks? I have always found that using a cusp tip as a reference point is difficult. The file frequently must be bent against the cavosurface margin of the axial wall of the pulp chamber so that it reaches the tip of a cusp. The plane of the rubber stop cannot be perpendicular to the long axis of the file and parallel to the plane of the occlusal surface at the same time. Instead, it is somewhat angled; there is some inaccuracy in this technique. When I push the rubber stop down to the cusp tip, sometimes I accidentally push it too far, and then I have to push it back up again because the cusp tip is pointed and does not make a good positive seat for me to push the rubber stop against.
|Figure 1. Using cusp tips or variable anatomic landmarks as endodontic reference points can lead to accuracy problems.|
Then, I have to call out the reference point to the assistant and she has to write it down. Sometimes during the procedure I forget which reference point I used and have to ask the assistant, who then has to stop and look at the chart and call out the reference point to me. This all takes time, and is arduous and inefficient. It also leaves room for transcription errors and mistakes. A percentage of the time a clinician will use a particular reference point from memory, when in fact it was a different reference point, leading to inaccuracy in the final fill (Figure 1).
THE SOLUTION: TOOTH FLATTENING
Figure 2.Tooth flattening eliminates the need to use such variable reference points.
Tooth flattening is the solution to the aforementioned problems (Figure 2). Gone are reference points. Once straight-line access is achieved, the file shaft sits nicely along the axial wall of the pulp chamber, and the rubber stop fits firmly on the flattened tooth surface perpendicular to the file shaft. There is no need to mark a reference point, and accuracy is greatly enhanced; time and effort are saved. Not only that, but a huge bonus is the fact that there is a much greater chance of at least 2 canals being of an identical length.
The time saved in resetting rubber stops is significant, since canal machining requires such an enormous number of multiple, repetitive movements. This allows the clinician to move from canal to canal without pulling the file completely out of the mouth and resetting the rubber stop on the file. Recalibration movements are cut by a third.
THE TOOTH-FLATTENING TECHNIQUE
This procedure allows for easier access. Tooth flattening is simple and quick to accomplish. In terms of efficiency gains, it’s impact is stunning. One of the complaints I hear the most from general dentists when it comes to performing endodontics is lack of good access. Many dentists automatically refer out maxillary second molar endodontics because of the frustration and difficulty of placing files in the canal orifices.
Figure 3. Tooth flattening is a quick, simple procedure.
The procedure consists of one simple step: the tooth is quickly flattened using a wheel diamond (Figure 3). The proven advantages are as follows:
• Greater accuracy in apical positioning. Because you will be measuring from a flat, uniform surface, the accuracy of your apical measurements will be easier to achieve.
• Less effort in access. It is easier to cut a 2-dimensional shape into a 2-dimensional surface than into a 3-dimensional surface.
|Figure 4. Tooth flattening makes it easier to puncture through the roof of the pulp chamber because most of the enamel is removed and the bur primarily encounters dentin.|
• Easier to puncture through the pulp chamber roof. When making a puncture through the roof of the pulp chamber, there is less resistance to the bur, since most of the enamel is gone and the bur tip primarily encounters dentin (Figure 4). Gaining access requires much less effort. Greater tactile sensitivity is achieved, making for more precise access. Because you have removed much of the material that your bur would encounter, you can literally feel the axial wall of the pulp chamber. Typically, the surface area encountered when cutting from the side is such that you cannot “feel” the axial wall of the pulp chamber. Using tooth flattening, resistance to the bur is reduced a great deal (both by the lack of hard enamel and less dentin), and a greater percentage of bur length can encounter the axial wall. Additionally, it is much easier to see the outline your bur is making without cusp tips blocking your vision. This is especially true when using electric handpieces at low rpm.
• Less side resistance. There is much less resistance to a side-cutting bur as well, for the same reason as stated above. Again, there is less material to cut through.
• Better chance of identical file lengths. The flat surface will make each canal closer in length. This means that each canal will be more uniform in comparison to those around it. Also, the distance from your measuring point to the apex will be much closer between canals.
• Elimination of recalibration. Because canal lengths will be identical more often, there will often be no need for recalibration.
• Elimination of reference point inefficiencies. Transcription errors are minimized because there is less information to record. You will be less likely to have to remember as much or make mistakes in recording or remembering these lengths.
One of the maddening things that happens to us when we are performing root canal treatment is that we forget which length each canal was; in addition, we forget which reference point we used. True, usually we tend to use the same reference points, but occasionally we deviate from our habits due to some alternative nuance in the tooth anatomy and/or canal anatomy. When each canal length is different and when each reference point is different, and when you are using reference points that deviate from the ones you usually use, you are really in trouble when it comes to memory. Tooth flattening simplifies the issue of reference points.
Tooth flattening substantially reduces the number of problems associated with access. This quick, simple step allows more clear and consistent access, which allows for a higher quality of treatment with less room for error.
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