With good case selection, NiTi rotary files are very effective and efficient for removing gutta percha. NiTi instruments are used for shaping canals at a speed of approximately 300 RPM. For rotary removal of gutta percha, I recommend the ProTaper Retreatment instruments (D1-D3, Dentsply Tulsa Dental) at approximately 500-750 RPM as greater rotational speed is necessary to create the friction and heat necessary to thermosoften gutta percha. The blades of these nickel titanium instruments engage softened gutta percha and effectively auger this material out of a root canal space. Certainly, hand files in the presence of a chemical, such as chloroform, is another important method to remove gutta percha from smaller and more curved canals. Chloroform rapidly softens gutta percha and, in conjunction with files, allows for the removal of gutta percha in a crown-down manner. With the canals filled with chloroform bath then paper points are utilized to wick residual gutta percha and sealers from the more inaccessible regions of the root canal system. In addition, I also refer you to my Ruddle on Retreatment DVD "Nonsurgical Removal of Gutta Percha, Silver Points, Carriers & Paste Fillers" as this tape shows a variety of strategies, devices and techniques to remove gutta percha.
For years I have recommended nickel titanium rotary instruments to augur gutta percha out of canals. My removal method has been coronal 1/3, middle 1/3, apical 1/3; eliminating gutta percha in a crown-down manner. The ProTaper Retreatment series (D1-D3, Dentsply Tulsa Dental) work safely and efficiently in this manner. This goes a long ways towards preventing the possibility of pushing gutta percha through the foramen, whether you're dealing with heat- or chemically-softened gutta percha. Removing gutta percha requires higher RPM's than for cleaning and shaping procedures. As mentioned above, I have typically recommended speeds around 500-750 RPM. The bottom line is whatever speed creates enough friction that mechanically softens and augurs out gutta percha is fine. I strongly recommend removing all gutta percha from the root canal prior to commencing with cleaning and shaping procedures. If a NiTi rotary file’s taper is too large to accomplish this goal, then use smaller tapered NiTi rotary instruments first. In more underprepared canals, or anatomically challenging canals, use 0.02 tapered stainless steel hand files in the presence of a solvent such as chloroform.
In regards to your question about chloroform versus xylol, I think chloroform is perhaps a little more effective in the removal of gutta percha and residual sealers. It works faster and more efficiently and if you use it carefully, I don't think you need to worry about any adverse clinical effects. Xylol is fine, but, in my opinion, will take a little longer to accomplish the same task.
An important method to remove gutta percha, especially when the canal has been overextended vertically and underfilled laterally, is to utilize the hedstroem displacement technique. The gutta percha is first thermosoftened with heat and then a 35, 40, or 45 hedstroem file is passively rotated clockwise into this mass. Let the gutta percha cool and harden within the blades, and upon withdrawing the hedstroem file, oftentimes the entire mass of gutta percha will be removed as well.
The first thing I consider when removing silver points is careful access. In many instances a silver point extends out of the canal and into the pulp chamber. Clinicians need to thoughtfully perform access so as not to inadvertently foreshorten a silver point which could result in making it more difficult to grasp and pull out. It’s important to remove all circumferential material surrounding the silver point to facilitate loosening and removal. A grasping tool such as the Stieglitz pliers (Henry Schein) can generally get a strong purchase on the coronal end of a silver point and then, utilizing the concept of fulcrum mechanics, elevate the silver point out of the canal.
Indirect ultrasonics is another important method to remove silver points. It is not wise to place any ultrasonic instrument directly on the silver point because it will rapidly erode away this soft material. Rather, first engage the silver point with a grasping instrument and then place an ultrasonic instrument, such as a ProUltra Endo Tip #1 (Dentsply Tulsa Dental), on the pliers to indirectly vibrate it loose. Since most canals are irregular in their cross-sectional dimensions and since silver points are round, then theoretically, space exists between the wall of the canal and the silver point. Files, solvents, and chelators can be utilized to eliminate sealer thus undermining and loosening the silver point so it can be removed. The hedstroem displacement technique is an invaluable technique for removing silver points or silver point segments. Finally, microtubes can be utilized to engage and remove certain silver points. The Post Removal System (PRS, SybronEndo) has small microtubular taps, allowing the clinician to mechanically tap and engage any silver point that is 0.6 mm or greater in diameter and whose most coronal extent extends into the pulp chamber. For further technique information on the removal of silverpoints, see also the Ruddle on Retreatment DVD entitled "Nonsurgical Removal of Gutta Percha, Silver Points, Carriers & Paste Fillers".
The successful removal of carrier-based obturators utilizes the same techniques for removing gutta percha and silver points. Oftentimes, the biggest secret to remove a carrier is patience and perseverance. For further technique information on the removal of carrier-based obturators, see also the Ruddle on Retreatment DVD entitled "Nonsurgical Removal of Gutta Percha, Silver Points, Carriers & Paste Fillers".
When evaluating a paste case for retreatment, it is wise to recognize that certain pastes are very difficult to remove because they set up brickhard. However, it is important to appreciate that due to the method of placement, the most dense portion of the paste is in the coronal one-third and the material is generally less dense moving in an apical direction. Ultrasonic instruments, in conjunction with the microscope, afford excellent control in removing paste from the straight-away portions of the canal. To remove paste apical to canal curvature, use a precurved stainless steel file attached to a specially designed “File Adapter” (SybronEndo) that hooks to the ultrasonic handpiece (P5, Dentsply Tulsa Dental). Other removal methods include heat, end-cutting rotary NiTi instruments, chemicals such as Endosolv R and Endosolv E (Endoco) and Micro-Debriders (Dentsply Maillefer). For further technique information on the removal of paste fillers, see also the Ruddle on Retreatment DVD entitled "Nonsurgical Removal of Gutta Percha, Silver Points, Carriers & Paste Fillers".