Silver points are still available today for obturation of root canals, but their users are becoming fewer and fewer. This is fortunate, as they are obviously a poor choice of material to fulfill our aim of hermetically sealing the root canal system. These points corrode over time and allow high levels of leakage. If you’re particularly interested in the mode of failure, check out the following references:
Seltzer S, Green DB, Weiner N, DeRenzis F.
A scanning electron microscope examination of silver cones removed from endodontically treated teeth.
Oral Surg Oral Med Oral Pathol 1972;33:587–605.
Zielke DR, Brady JM, del Rio CE.
Corrosion of silver cones in bone: a scanning electron microscope and microprobe analysis.
J Endod 1975;1:356–60.
Relation between corroded silver points and endodontic failures.
J Endod 1981;7:224–7.
Zmener O, Dominquez FV.
Corrosion of silver cones in the subcutaneous connective tissue of the rat: a preliminary scanning
electron microscope, electron microprobe, and histological study.
J Endod 1985;11:55–61.
Silver points for root canal obturation, however have been used extensively in the past, and this means that we will be required to remove them for the purposes of re-treatment. Many younger dentists will never have been introduced to the silver point technique, and may never have even handled one.
The main thing to note is that the silver point is quite soft and malleable. It is also smooth, which means that it does not generally bind in the canal. The points were cemented into the canals with sealer, and generally, the point was left protruding into the canal and the core material placed around it. Thus, If you can manage to retain this free end and grasp it, it can often be pulled free of the canal, especially if there has been extensive microleakage. Where a point has been sheared off at or below the level of the orifice, it can be much more difficult to remove.
The first step in removing a silver point is to carefully remove any core material from around the point. The softness of the point does, however mean that caution must be used when exposing the free end of the point. both burs and ultrasonics can quite easily cut through through the point leaving you little to grab on to. So, I generally use an ultrasonic instrument to remove the core material. If the core material is harder – composite or amalgam and you don’t have specialised endodontic ultrasonic points, then take great care when removing the core material with burs so as to ensure you don’t cut through the silver point.
Don’t worry if you don’t have specialised endodontic ultrasonics available, you can work with your general purpose ultrasonic tip, as long as you carefully remove much of the core material and then use the ultrasonic to free the silver point tags.
Once you have removed the core material, irrigate thoroughly with sodium hypochlorite. The next step is to try to free up the coronal portion of the silver point. A few drops of chloroform will help to dissolve some sealer if the sealer is ZOE based. You can then gently use a small file to try to break up the cement around the coronal portion of the point.
If the point appears to be a little loose, it’s time to start pulling. At this point, you might find that you have nothing small enough to reach into the pulp chamber to grab the free end of the point. Unfortunately, this is where you might find that some specialised equipment is required. The Steiglitz forceps are nice and small and generally will fit into a pulp chamber and allow you to grasp the free end.
Remember, the points are soft, so use firm and constant force to withdraw the point. Try to avoid bending back and forth as this can work harden the silver point and lead to a breakage.
Another technique mentioned in John Rhode’s Textbook, ‘Advanced Endodontics’ (quite a good read for an overview of advanced techniques) is to gently screw a hedstroem file down beside the point to engage it, and then attempt to withdraw the file with point attached.
OK, so what do you do if the point breaks, or you don’t have enough of a tag to grip with Steiglitz forceps, or you simply don’t have Steiglitz forceps? This can also occur if a post has been used and the point has been sheared off apically to the orifice. One method I was forced to try recently was the twisted file method. I’m not sure if this has a formal name (Just checked in Rhode’s Textbook – he calls it “Braiding”). Basically, you place three files alongside the point and twist them so the twisted files grip the point, and then simply pull. I’ve seen this technique described in text books for the removal of separated instruments also.
In this case, I used two Hedstrom files to bind the point, and a third, smaller (size 10) K file. I think the third file helps wrap the other two files around whatever it is you are trying to grab. When using just two files, they can just end up twisting around each other. The softness of the silver points also allows the Hedstrom to lock into the point.
When twisting the files, you need to keep some apical pressure so that they don’t slip off the subject of your grab. You do need to twist the files quite tightly to ensure you have a firm grip.
I’d love to hear thoughts and comments from other dentists and endodontists on their experiences and what method they use to remove silver points when re-treating.