Dental Tools and Mental Tools

Double Canal, Single Apex

Seattle, WA...May 21, 1994
Last Edited on Wednesday, January 14, 1998

Every artisan has tools. The more complex the work, the more tools needed. And the more mental tools needed to use them.

One of the most complex problems in endo concerns double canals that merge into a single common canal.

One of the most difficult cases occurs in mesial roots of lower molars and sometimes in canines and premolars.

The difficulty is in cleaning the area just apical to the point where the two canals join.

This is second only to knowing that you need to do this in the first place.

How to Detect

It really helps if you remember my rule of thumb that all lower teeth have two canals, one buccal and the other lingual.

If you take an x-ray directly from the buccal you will super-impose one on the other and you won't see anything of any use to you.

If you take all your mandibular xrays slightly from the mesial, looking at an xray will allow you to see the canals as separate entities and many times you can see in advance that you have this situation.

Other times you will not notice it until after you have filled and will need to remove the cement and start over.

The problem is that if you circumferentially file each of the two canals to about the 3mm point and then dress the apex there is frequently a isosceles triangle shaped area coronal to the single apex and between the two canals.

This triangle has its point down and a flat line across the top.

Just under that flat horizontal line is a flat bucco-lingual, ribbon shaped area loaded with debris.

Getting at this area is relatively simple if you know it is there and have Fine-Cut hand files available.

After you have circumferentially filed to about a size 40, pre-curve a size 30 in the apical 5 or 6 mm, insert it to about 2mm from the apex making sure that the tip of the file points to the buccal on the lingual canal and to the lingual on the buccal canal, and pull straight up with a long stroke that brings the file completely out of the orifice.

Then do the same with the other canal. Alternate like this 10 or 12 times, each time checking the curvature of the file for sharp bends.

Make sure that you have plenty of fresh water in the canal when you do this.

The best way to assure that you do is to use a number 15 file in a Fine-Cut Sonic adapter with a scaler for a few seconds between each stroke of the curved file.

Each stroke will cut on the inside of the curve and will eventually result in a canal that viewed from the mesial will look like a sergeants stripes, a shape that is easy to irrigate and to fill and it will be free of debris.

Very often you will notice when filling a canal of this shape, as you fill one canal, the cement will flow up the other.

The reason for this is that the path of least resistance is coronal, not apical because there is tissue fluid pressure at the apex and none above.

This is also an indication that the tip of the needle is in the trigone and not in the apex.

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