The Spectre of Retreatment

July 1, 2002
Retreating endodontic cases is a prospect that haunts every practitioner. These expert tips and solutions from the guys at Real World Endo can help dentists turn this frustrating endeavor into a profitable one.

by Kenneth Koch, DMD, and Dennis Brave, DDS

Retreating endodontic cases is a prospect that haunts every practitioner. These expert tips and solutions from the guys at Real World Endo can help dentists turn this frustrating endeavor into a profitable one.

All dentists will experience an increase in the number of endodontic retreatment cases. This is due to a number of factors such as more foreign patients and a greater desire among the population to retain their dentition. The "Spectre of Retreatment" looms ever nearer. But who should perform these retreatment cases?

We believe that general dentists can effectively manage retreatments. The key is to understand your ability and experience. What has made retreatment easier is the introduction of technology such as rotary files and ultrasonics. Two circumstances where you can perform retreatment with rotary files are gutta percha and carrier-based (Thermafil and GT Obturator) cases.

Gutta percha has been the standard for obturation for many years. Gutta percha obturation can be a result of either lateral or vertical condensation. Additionally, there are true thermoplastic techniques such as that achieved with the Obtura gutta percha gun. Historically, we have used solvents to soften and retreat the gutta percha. A modification of this technique has been to use a Touch 'n Heat to create a well that will hold the solvent. We have also utilized Gates Glidden burs or a System B to physically remove some of the "GP." However, what has changed retreatment most significantly has been the use of rotary files.

Rotary files, when used at an increased speed, will plasticize the gutta percha and remove it from the canal like an auger. This technique is so effective that you occasionally will see a lateral canal filled by the plasticized GP. This is very similar to a "compactor." The best way to perform the technique is by using the following sequence.

Begin with a No. 30 /.06 taper rotary file (K3 or Profile); run the file at an increased speed - we recommend 1250 RPM. Take this initial file to 2/3rds of the canal depth or just prior to any curve. Now, place a solvent into the prepared channel. We recommend chloroform, but if you have a problem with chloroform, you can use xylol (xylene). Following the placement of the solvent, go back in with the No. 30 /.06, but this time at the regular speed of 350 rpm. We now take this to length. An alternative in difficult cases is to introduce a No. 10 or No. 15 hand file and work to length. To make this technique even easier, use a Touch 'n Heat (or System B) at the beginning to plasticize the coronal 4-5 mm of gutta percha. The rotaries will then go through the gutta percha like butter. This is an incredibly efficient method of retreatment.

Additional tips

To obtain a working length during a retreatment case, you should take an X-ray of a file placed in the canal. Apex locators, even third generation, do not work well when the previous fill is near the end of the canal.

An alternative solvent to chloroform is oil of eucalyptus. Do not use rectified turpentine! We do not know where this started, but rectified turpentine does not work very well and it makes your operatory smell like a garage. Stay with the recommended solvents.

With the increased use of carrier-based systems, such as Densfil, Thermafil, and GT obturators, we face the prospect of sometimes retreating these carriers. If a Thermafil case must be retreated, it is usually because the preparation was inadequate; consequently, the carrier was stripped of gutta percha. To further understand how to retreat carriers, you must be aware of the different types. Thermafil carriers can be either metal (stainless steel or titanium) or plastic. The newer GT obturators are plastic carriers.

If you retreat an older case that employed a carrier, most likely this will be a metal (stainless steel) unit. To retreat a stainless case, we recommend initially using a heat source to heat the carrier and melt the gutta percha alongside the carrier. If the carrier is somewhat stripped of gutta percha, you will have "donuts" alongside the carrier in the canal. These "donuts" will give the impression of being stuck in an undercut. The carrier will be loose, but you will not be able to remove it in a vertical direction. However, by heating the carrier for 10 to 12 seconds (either with a Touch 'n Heat or System B), you often can plasticize the gutta percha alongside the carrier. Now grab it with a hemostat or steiglitz and remove it from the tooth. After removing the carrier, you can retreat the tooth like a regular GP case.

When in doubt, use a rotary file

If the retreatment case (Thermafil or GT obturator) is more recent, the carrier most likely will be plastic. When retreating plastic carriers, use rotary files. Take a No. 30 /.04 taper rotary file (K3 or Profile) and run it at 1250 rpm alongside the carrier until you are approximately half-way down the canal. Come out of the tooth and change to a larger tapered file. We recommend a .06 taper No. 30. If you do not have a greater taper file (.06), you can simply go to a larger .04 taper file such as a No. 35 or No. 40. However, this method works much better with the .06 taper. Proceed with the .06 taper at the regular speed of 350 rpm into the same channel preparation. The idea is that the greater taper (.06) will engage the carrier and give it some lift. Generally, the taper will not pull out the carrier in a single stroke. However, that is not the idea. We are merely trying to dislodge the carrier. If, after one side is completed and the carrier is not loose, repeat the same technique on the opposite side of the canal. Once the carrier is dislodged, grab it with either a steiglitz or hemostat, pull, and remove it from the tooth. Complete the remainder of the retreatment as you would with a regular gutta percha case. An important point to remember is that when retreating plastic carriers, keep the rotaries running alongside the long axis of the carrier. If the rotary file is angled, you may sever the plastic carrier. In that case, retreat as with option one. Knowledge destroys myths! The notion that carrier-based systems are impossible to retreat is exactly that - a myth!

Silver point cases

Silver point cases and paste retreatments are other examples where modern technology can come to the rescue. The introduction of piezo electric ultrasonics has been particularly helpful. Not only do these units give us more BPS (beats per second), but their mode of action is very attractive to endodontists. Regular magnostrictive ultrasonics create a figure-8 motion while the piezo electric units work in a back and forth, linear manner. One ultrasonic we especially like is the mini Endo by Sybron Endo.

Silver-point cases were very popular and were still being placed up until the mid-1970s. The basic problem with the silver point technique is the point itself. Silver points are round while most root canals are not. Consequently, a number of these cases have microleakage problems, which explains their high failure rate. We see a lot of corrosion products from failed silver points, and, when removed from the canal, they are actually black. As a result of this contamination, silver point retreats have a higher incidence of flare-ups. Therefore, we recommend doing a symptomatic case - one with pain or swelling present - in two visits. In this instance, the intracanal medication of choice is calcium hydroxide.

How do we successfully retreat these cases? The first thing to do is to take an X-ray and determine where the silver point ends. Is it in the tooth or is it over-extended? The next stage is core reduction and identification of the silver point. Dentists who did silver points often extended the points up into the chamber and then packed amalgam around them. The results were comparable to reinforced concrete. When reducing the core, you must proceed carefully so that you do not sever the silver point. Using magnification is a must with these cases. Silver is a soft metal so it is easy to cut. Accidentally severing the silver point makes the case more difficult. Once the core has been removed and the point has been identified and isolated, you can then frequently remove it. When they do extend above he orifice, silver points generally can be removed simply by grabbing them with a steiglitz or a silver-point remover. For those stubborn points that simply won't budge, we recommended the following technique. Trough around the silver point with an ultrasonic spreader tip. The idea is to break the seal between the silver point and the canal wall. Exercise extreme care to ensure that you follow the long axis of the point. The vibration generated by the spreader tip will most often loosen the silver point. Grab the point with a steiglitz forceps or hemostat and remove. This procedure is predictable if you utilize a piezo electric ultrasonic and magnification.

Another technique for removing silver points is to use a hedstrom file. This works especially well when the silver point has been cut off (as in a post preparation). Take the hedstrom and run it down alongside the silver point until it binds. Make a clockwise quarter turn. This will engage the flutes of the hedstrom into the soft silver point. Once engaged, pull coronally, using a firm, confident tug.

Foreign pastes

Foreign paste removal is another retreatment issue where rotaries and ultrasonics increase your chance of success. In these cases, you must initially establish what type of paste is in the canal. A clue to this is determining which country the case was completed in and the color of the paste.

Reddish-orange paste (which stains the chamber) is usually a resin-based paste like endomethasone and is frequently seen in Chinese and eastern European patients. Septodont makes an excellent solvent (Endo Solv R) to help retreat these challenging cases. Once the solvent starts to work, rotaries can expedite the retreatment. White generally indicates an eugenol-based paste. These can easily be treated with chloroform (or xylol) and rotaries. However, if the paste is cream-colored and was completed in Russia, you have a serious challenge on your hands. Endodontic restorations done in Russia are among the most difficult to retreat due to the high concentration of zinc phosphate in the paste. Piezo electric ultrasonics are a big help in these cases, as is sound clinical judgment. Sometimes, you remove the paste from the palatal root, but you can't gain any additional length. It can be like concrete! Be careful; too often, we have seen these cases overtreated where the dentist ends up perforating or destroying the tooth. The Russian paste retreatment cases are best referred to an endodontist. They are not easy, even for an experienced specialist.

As we stated earlier, many general dentists are qualified to do some retreatment cases. However, if you attempt retreatments, you must have the right equipment! Many retreatment cases will involve removal of a post. There are many expensive gadgets available that don't work as well as advertised. Furthermore, some of

these have problems with freeway space in the posterior part of the mouth. Post extractors should only be used as a last resort. Endodontists prefer to remove posts with an ultrasonic. Ultrasonics are a tremendous help in post removal. Here are some tips you should know (see also the December 2001 issue of Dental Economics.)

When removing a post, it is critical to break the seal between the post and the tooth structure. This can be initiated through the use of a surgical length 1/4 round bur. This is technique sensitive so be careful to go along the long axis of the root. Once you have trephinated around the post, you can place a water-cooled ultrasonic tip into the trough. A basic spreader tip will do fine. This will further break the cement or resin, and you eventually will notice motion in the post. Sometimes, you actually can place a spreader tip against the post itself. This works well if the seal has been broken. Another option is to clamp the post with a hemostat and then vibrate the hemostat with an ultrasonic tip. However, do not clamp the post directly with a hemostat and then try to "muscle it." With the new, stronger anaerobic resin cements, if you "muscle" a post, and hear a crack, guess what? You just cracked the tooth. Take your time and don't rush - the post will come out. We strongly recommend using spreader tips with water spray. If you run a spreader tip dry, a couple of things happen, none of which are good. For one thing, the hand piece on some units becomes very hot and the ultrasonic tip gets overheated. Secondly, the post becomes heated; this heat can eventually be transferred to the periodontal ligament. Additionally, excess heat may result in microfracture of the dentin. Lastly, when using an ultrasonic without water spray, you will have an increased smell of burning dentin. These dilemmas can be avoided through the use of an ultrasonic tip with a water port. If you want to use the ultrasonic "dry" for a few seconds, simply turn off the water. More importantly, if the tip has a water port, the water is there when you need it.

The spectre of retreatment is always with us. However, with modern technology, these cases can be handled predictably. The key is to apply the new technology and to understand your limits. Know your limits both in terms of technical expertise and philosophy. We have given you some insight into retreatment issues that we hope will make your life easier. As usual, we will continue to give you "Just the Facts, Nothing but the Facts."

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