Removal of root filling materials techniques, outcomes and risks

Techniques, Outcomes and Risks for removal of root filling materials.
Retreatment in endodontics starts with the removal of the root filling material, this seminar covers different technique in the removal of root filling materials "mainly GP" but other materials are also covered.

1. Removal of root filling materials: Techniques, Outcomes and Risks IBRAHIM BAYRAM BDS, MFD RCSI, MFDS RCPSG MClinDent student (PROS), Cardiff university

2. Introduction The aim of non-surgical root canal re-treatment is to: Relieve patient symptoms. Re-establish healthy periapical tissues following failure of initial therapy. By removing materials from the root canal space, chemically disinfecting canals and if present, addressing deficiencies of pathological or iatrogenic origin. (Virdee and Thomas, 2017)

3. Introduction GP may be removed mechanically using hand or rotary instruments aided by heat, solvents or ultrasound. The technique is dependent on: The clinical situation. The quality of the GP root filling. Personal preference and experience. (Duncan and Chong, 2011)

4. Pre-treatment evaluation Assessment (evaluating difficulty of GP removal): Clinical and radiographic evaluation of coronal restoration and core material for gaining adequate access. Radiographic examination of canal filling in terms of condensation quality, voids and length. Iatrogenic injuries, such as ledges, separated files and perforations. Root morphology, atypical and curved canals.

5. Gutta-Percha Removal One of the great advantages of using gutta-percha for root filling is its relative ease of removal. Upon access, it is usually relatively easy to find the treated canal orifices with the visible pink gutta-percha material inside. Initial probing with an endodontic explorer into the material can help rule out the possibility that there is a solid core carrier. If there is a plastic carrier, then heat should not be used to remove the coronal gutta-percha. Heat should be applied in a short burst to allow the instrument to penetrate the gutta-percha mass, followed by cooling, which will cause the material to adhere to the heat carrier facilitating its removal. After removing as much gutta-percha as possible with the heated instrument, then remove any remaining coronal material with small Gates-Glidden drills, taking care not to over enlarge the cervical portion of the canal.

6. Gutta-Percha Removal Probe the canal using a #10 or #15 K-file. It is sometimes possible to remove or bypass the existing cones of gutta-percha if the canal has been poorly obturated, thus eliminating the need for solvents. If that is not possible, then a gutta-percha solvent must be used to remove the remaining material in the apical portion of the canal.

7. Hand files It may be possible to insert a Hedstrom file (size #25 or more) alongside the loose gutta-percha root filling. The size of the Hedstrom file is chosen so that it will engage the loose gutta-percha root filling but not the canal wall. Hedstrom file is rotated a quarter-turn clockwise to further ensure engagement with the gutta-percha root filling and when the file is withdrawn from the canal, it should pull out the loose root filling. This technique is less likely to be effective if the gutta-percha root filling is well condensed.

8. Overextended gutta-percha removal Overextended gutta-percha removal can be attempted by inserting a new Hedstrom file into the extruded apical fragment of root filling using a gentle clockwise rotation to a depth of 0.5 to 1 mm beyond the apical constriction, which may engage the overextended obturation. The file is then slowly and firmly withdrawn with no rotation, removing the overextended material. This technique works frequently, but care must be taken not to force the instrument apically, which furthers the extrusion of the gutta-percha; in addition, the file may separate. The overextended apical fragment should not be softened with solvent , as this application can decrease the likelihood of the Hedstrom file getting a solid purchase of the apical extrusion.

9. Removal of overextended gutta-percha A, Preoperative radiograph showing overextended filling material. B, A small Hedstrom file pierces the overextended material and retrieves it. C, The 18-month reevaluation. The tooth is asymptomatic.

10. Rotary Files Using rotary systems to remove gutta-percha in the canals has been advocated due to enhanced efficiency and effectiveness in removing gutta-percha from treated root canals. The dedicated retreatment files have end-cutting tips to enhance penetration and removal of the root filling mass, thus increasing their efficiency A rotary NiTi file of a suitable size is chosen so that the cutting flutes will engage the root filling and not the canal wall. When activated, the flutes should propel the GP out of the canal. The main risk: danger of instrument fracture. This may be reduced by not applying excessive apical pressure and keeping within the recommended speed and torque limits of the chosen rotary system. Take care from heat generation and keep away from dentin. It is recommended that after rotary gutta-percha removal, subsequent hand instrumentation is needed to remove the residual obturating materials completely from the canal.

11. Efficacy of ProTaper Universal Retreatment Files in Removing Filling Materials during Root Canal Retreatment Aim: To evaluate the efficacy of the ProTaper Universal System rotary retreatment system and of Profile 0.06 and hand instruments (K-file) in the removal of root filling materials. Methods: Forty-two extracted single-rooted anterior teeth were selected. The root canals were enlarged with nickel-titanium (NiTi) rotary files, filled with gutta-percha and sealer, and randomly divided into 3 experimental groups. The filling materials were removed with solvent in conjunction with one of the following devices and techniques: the ProTaper Universal System for retreatment, ProFile 0.06, and hand instruments (K-file). The roots were longitudinally sectioned, and the image of the root surface was photographed. Results: The group that showed better results for removing filling materials was the ProTaper Universal System for retreatment files, whereas the group of ProFile rotary instruments yielded better root canal cleanliness than the hand instruments, even though there was no statistically significant difference. Conclusion: The ProTaper Universal System for retreatment files left cleaner root canal walls than the K-file hand instruments and the ProFile Rotary instruments, although none of the devices used guaranteed complete removal of the filling materials. The rotary NiTi system proved to be faster than hand instruments in removing root filling materials. Valentina Giuliani et al. 2008

12. Efficacy of Different Rotary Instruments for Gutta-Percha Removal in Root Canal Retreatment Aim: To evaluate the efficiency of FlexMaster, ProTaper, and RaCe rotary instruments compared with Hedström files for removal of gutta-percha during retreatment. Methods: Sixty mandibular premolars with one single straight canal were instrumented with K-type files and filled using cold lateral compaction and sealer. The teeth were randomly divided into four groups of 15 specimens each. After re-preparation with Gates Glidden burs and the test instruments the specimens were cleared. The area of remaining gutta-percha/sealer on the root canal wall was measured from two directions. Results: The RaCe group showed significantly less residual obturation material than FlexMaster and Hedström group (p 0.05; closed test procedure). There was no difference between ProTaper and all other instruments (p 0.05). ProTaper and RaCe instruments required significantly less time for retreatment than FlexMaster and Hedström files (p 0.05). One RaCe file, two ProTaper, and two FlexMaster instruments separated. Conclusion: RaCe cleaned obturated canals more effectively than hand files and FlexMaster files. Schirrmeister et al. 2006

13. Three-dimensional Evaluation of Effectiveness of Hand and Rotary Instrumentation for Retreatment of Canals Filled with Different Materials Aim: To measure the remaining filling volume of different obturation materials from root-filled extracted teeth by using 2 removal techniques. Methods: Eighty single-rooted teeth were collected and decoronated, and the root canal was prepared by using the ProTaper nickel-titanium rotary files. The teeth were randomly allocated into 4 groups, and each group was obturated by using a different material. Group 1 was filled with gutta-percha and TubliSeal sealer, group 2 was filled with EndoRez points and EndoRez sealer, group 3 was filled with RealSeal points and RealSeal sealer, and Group 4 was filled with a gutta-percha point and GuttaFlow sealer. Teeth were scanned with a micro– computed tomography scan, and then root fillings were removed by using ProTaper retreatment files or hand K-files. Teeth were scanned again, and volume measurements were carried out with micro– computed tomography software. Conclusion: The present study showed that all tested filling materials were not completely removed during retreatment by using hand or rotary files. Gutta-percha was more efficiently removed by using hand K-files. Hammad et al. 2008

14. Efficacy of ProTaper Retreatment System in Root Canals Filled with Gutta-Percha and Two Endodontic Sealers Aim: This in vitro study evaluated comparatively the efficacy of the ProTaper Universal (Tulsa Dental, Tulsa, OK) rotary retreatment system and hand files for removal of filling material during root canal retreatment and the influence of the type of sealer on the presence of filling debris in the re-instrumented canals. Methods: The canals of 60 palatal roots of first molars were obturated with gutta-percha and either a zinc oxide–eugenol–based or a resin-based sealer and re-instrumented: G1, EndoFill/hand files; G2, AH Plus/hand files; G3, EndoFill/ProTaper; G4, AH Plus/ProTaper. Roots were cleaved and examined with an optical microscope, and the amount of filling debris on canal walls was analyzed on digitized images. Conclusion: All groups presented filling debris in the 3 canal thirds after re-instrumentation. Vinícius Reis Só et al. 2008

15. Heat Using pluggers or heat carriers, electrically-heated spreaders or pluggers, such as the Touch ‘n Heat or System B Heat Source. Any softened gutta-percha clinging to the cooling spreader or plugger will be removed when the instrument is withdrawn. The rest of the softened gutta-percha in the canal is then removed with either hand or rotary NiTi files as mentioned previously. The procedure repeated until all of the root f illing material is removed. The heated instrument should be applied in intermittent short bursts and only in the straight part of the root canal.

16. Solvents Solvents have been advocated for many years to soften GP and assist in its removal. A solvent is usually needed to remove well-condensed gutta-percha. Traditionally, Chloroform was the solvent of choice and has been shown most effective . ( Tamse et. al, 1986, Wilcox 1995). However, issues regarding cytotoxicity if it comes into contact with periapical tissues have been raised, and it has been classified as a potential carcinogen by the food and drug administration (1976). And a potential risk to the dental team. O n the other hand, their is limited evidence of carcinogenicity. When used carefully, chloroform is regarded as a safe and effective endodontic solvent.

17. Solvents Eucalyptol Xylene/ xylol Methylchloroform Tetrahydrofuran Methylene chloride Halothane Rectified turpentine Orange solvent Tetrachloroethylene (EndosolvE) In general, all solvents are toxic to some degree and their use should be limited or avoided if not needed. (Barbosa et. al, 1994).

18. Solvents Xylene and eucalyptol dissolve gutta-percha slowly and only approach the effectiveness of chloroform when heated. Rectified turpentine has a higher level of toxicity than chloroform, and it produces a very pungent odor in the operatory. Halothane has been shown to be as effective a solvent as chloroform in several studies, but a more recent study indicated that the time for removal of the root filling was longer than when using chloroform. The increased cost and volatility of halothane and the potential for idiosyncratic hepatic necrosis make it less desirable to use as a gutta-percha solvent. Although methylchloroform is less toxic than chloroform, it is also less effective as a solvent for gutta-percha. Both halothane and chloroform have been shown to affect the chemical composition of dentin and may affect bonding strengths of adhesive cements to the altered dentin.

19. Evaluation of alternatives to chloroform in endodontic practice Wennberg, Ørstavik (1989) In this study, methylene chloride, methyl chloroform, tetrahydrofuran, xylol and eucalyptol were tested for their capacity to dissolve or soften gutta-percha points compared with chloroform. The effect of the test solvents was assessed by measuring the depth of penetration of a small indentor of fixed weight and shape into a gutta-percha disk covered with the test solution for various time periods. Chloroform showed the most pronounced effect, followed by methylene chloride, tetrahydrofuran, and methyl chloroform. When both occupational health and gutta-percha solvent capacity were considered, Methyl chloroform seemed to be an interesting alternative to chloroform.

20. Solvents Using an irrigating syringe , the selected solvent is introduced into the coronal portions of the canals, which will then act as a reservoir for the solvent. Then, small hand files (sizes #15 and 20) are used to penetrate the remaining root filling and increase the surface area of the gutta-percha to enhance its dissolution. This procedure can be facilitated by using precurved, rigid files such as the C+ file (Dentsply Maillefer).

21. Ultrasonic A small size (e.g. size 15) endosonic file will suffice as it is not used to physically engage the root filling, not used commonly. The technique relies primarily on a combination of irrigation and ultrasonic vibration to loosen the root filling, allowing it to be ‘‘floated’’ passively out of the canal. The technique carries a very much lower risk of instrument fracture. The endosonic file must not be run dry as the GP will be plasticized by the energized file, making it difficult to remove the root filling intact.

22. Ultrasonic The use of ultrasound in re-treatment is generally confined to hard pastes cements and sealers such as GI cements or as final debridement. Ultrasonic files activated without irrigation create frictional heat and can be used to plasticize gutta-percha, hence facilitating its removal. Disadvantages: The thermoplasticized gutta-percha tends to be forced against the root canal wall, creating considerable debris; furthermore, the ultrasonic files can only be used in the straight part of the canal. (Friedman, Moshonov and Trope 1993).

23. Laser A laboratory study investigated the potential application of a Nd:YAG laser in root canal re-treatment used in a dry root canal. It was utilized alone or in combination with hand instruments to remove various canal sealers and broken instruments . There was concern about the excessive heat generated and the safety parameters so the study was described as preliminary in nature. The use of the Nd:YAG laser for removal of GP and fractured files. It was found that laser irradiation was capable of softening GP and the addition of solvents did not improve the re-treatment process either in terms of the time required for removal or the amount of gutta-percha remnants. (Vidueic et. al, 2003).

24. Removal of Thermafil GP A gutta-percha carrier device or obturator is comprised of GP molded around a plastic or metal carrier. Retreatment of solid core materials is considered to be more complex and difficult than is the case with removal of gutta-percha alone due to the presence of the solid carrier within the mass of gutta-percha. The nature of the carrier and the level at which the metal carrier is severed will determine the method used and complexity of the retrieval. Three types of carriers are found in these systems: metal (stainless steel or titanium), plastic, and modified gutta-percha. It is advantageous to determine prior to initiating treatment if there is a solid core obturation in the root-filled tooth. The preoperative radiograph may show this because the stainless steel carriers will exhibit a fluting effect on the radiograph; however, the titanium carriers rarely are distinguishable from gutta-percha, and the plastic ones never are. Unfortunately, in most instances, the clinician finds that he or she is dealing with a carrier-based obturator after initial access to the pulp chamber.

25. Most studies employed traditional techniques in which one or more Hedstrom or K-files were used to engage the plastic carrier and extract the Thermafil obturator; with or without solvent. The principal difference between the removal of plastic and metal carriers is that the former deforms when heat is applied. As a result, a variety of other techniques in addition to traditional hand files and solvent can be used to facilitate removal. Rotary techniques using either rotary NiTi files or Gates Glidden . The removal of Thermafil can be problematic if the gutta-percha was stripped from the carrier. This makes it very difficult to insert a hand or rotary file alongside the carrier as there is no surrounding GP. The manufacturers have attempted to address this by producing only GP devices with plastic carriers and placing a notch running along one side of the carrier to provide space in order to allow file insertion and to facilitate removal. Removal of Thermafil GP

26. Effectiveness of Three Different Retreatment Techniques in Canals Filled With Compacted Gutta-Percha or Thermafil: A Scanning Electron Microscope Study Aim: To undertake an SEM investigation into the effectiveness of 3 different retreatment methods (ultrasonic tips, NiTi rotary instruments, and K-file manual instruments) in removing warm vertically condensed gutta-percha or Thermafil filling material from previously in vitro filled root canals. Method: Thirty-six extracted roots were filled by using AH Plus as a sealer with Thermafil (18 roots) or warm vertically condensed gutta-percha (18 roots). All fillings were removed up to the middle third by using Gates Glidden drills. The retreatment was completed by using K-files (group 1), M-Two NiTi rotary instruments (group 2), or ESI ultrasonic tips (group 3) in 12 roots each. Root canals were irrigated by using 10% EDTA and 2.5% NaOCl . The samples were split longitudinally and observed by scanning electron microscopy (100–2000X). Conclusions: All retreatment techniques showed similar performances in terms of smear layer morphology, debris, and surface profile. None of them completely removed filling debris from dentinal tubules of apical third. Pirani et al. 2009

27. Resilon Removal Resilon (Resilon Research LLC) is a thermoplastic polyester polymer that is bonded into the canal space using an unfilled resin bonding system (Epiphany, SybroEndo, Orange, CA). Resin-bonded obturation systems have been advocated in the past; however, the difficulty to retreat canals filled with this obturating material has prevented its widespread use. The Resilon polymer itself is reported by the manufacturer to be soluble in chloroform and may be removed by heat application, a behavior that is similar to gutta-percha. There may also be a problem with removal of the unfilled Epiphany resin sealer, especially because the sealer tags have been shown to penetrate deep into dentinal tubules and presumably also into anatomic ramifications of the canal that need cleaning during retreatment.

28. Resilon Removal After the Resilon core has been removed using heat and chloroform, the authors would recommend the use of a resin solvent such as Endosolv-R (Septodont, Paris, France) to attempt elimination of the unfilled resin sealer prior to instrumentation.

29. Paste Retreatment Many of the pastes used, such as N2 or RC2B, contain formaldehyde and heavy metal oxides and so are toxic and potentially present a danger to the patient’s health, both local and systemic, if overextended beyond the confines of the root canal system. For purposes of retreatment, paste fills can be categorized as soft or hard, and all should be considered potentially toxic. Great care should be exercised when removing the paste to avoid overextension, potentially severe postoperative pain, and possible paresthesia/dysesthesia from the paste’s potential neurotoxicity. Soft pastes are generally easy to remove using crown down instrumentation with copious sodium hypochlorite irrigation to minimize extrusion. Greater difficulty arises when the paste is set hard.

30. Paste Retreatment Following access preparation and coronal orifice exposure, the paste is probed with an endodontic explorer and files. If hard and impenetrable, then the coronal paste can be removed with burs or a straight, tapered ultrasonic tip in the easily accessible straight portions of the canal using magnification and illumination. Once the canal curvature is reached, further use of this method will result in damage to the canal walls and possible perforation. Precurved, small hand files are inserted to probe the apical area. Many times the density of the paste filling material decreases in the apical extent of the fill so that penetration to the apex may be possible. If not, a solvent must be used to attempt to soften the remaining paste. The choice of solvent is usually made by trial and error starting with chloroform. If that does not soften the material in a reasonable amount of time and does not allow penetration with small files, then the chloroform is wicked out of the canal and another solvent is chosen. There are two frequently used solvents for paste fills: Endosolv-E and Endosolv-R (Septodont, Paris, France). The Endosolv-E is selected if the paste contains zinc oxide an eugenol, and the Endosolv-R is chosen for resin-based pastes.

31. Paste Retreatment The chosen solvent should be placed in the access, and attempts should be made to penetrate the paste with hand or ultrasonic files; however, care must be taken to avoid creating a ledge or other defect in the canal that may preclude successful retreatment. The progress is frequently slow, and the clinician may elect to leave some solvent in the canals between appointments to soften the paste. Ultrasonically activated files have been advocated for use in penetrating hard-set pastes in the curved apical segments of canals. The ultrasonic energy breaks up the paste, and the irrigation floats the fragments in a coronal direction until the apical terminus is reached. This technique is reported to be time consuming, and care must be exercised to avoid instrument separation, perforations, or alteration of canal morphology. On occasion despite all best efforts, the paste cannot be removed from the tooth, so apical surgery or extraction should be considered in these cases.

32. Silver Point Removal Many of the same techniques described for removing separated instruments in the following section apply to the removal of silver points. Silver points have a minimal taper and are smoothed sided, and corrosion may loosen the cone within the preparation. Therefore, the clinician should encounter a much easier time removing them than would be the case with separated instruments, which may be mechanically engaged into canals. Silver point canal preparation techniques produced a milled, round preparation in the apical 2 to 3 mm of the canal and, coronal to that, the clinician will frequently find space between the round silver point and the flared canal walls that can usually be negotiated with hand files facilitating point removal.

33. Uncovering the head of the silver point with ultrasound, taking care not to touch the silver point to avoid weakening or fracturing it. loosened by removing whatever is encasing it (e.g . Solvent to remove sealers surrounding it) . If the head of the silver point is visible and it can be engaged with a surgical hemostat, artery forceps, a spoon excavator, or specially designed instruments such as Stieglitz forceps, removal may be executed. Consider using the braided Hedstrom file technique . Silver Point Removal

34. If this proves impossible, specialized kits are available which generally work on the principle of trephination: Masseran kit: A selection of trephines. Cancellier kit or Endo extractor: A series of 4 hollow tubes; the required size is chosen and cyanoacrylate adhesive is used to facilitate removal. Meitrac system : A set of trephines and extractors; principally for use in the coronal aspect of the canal. Instrument Removal System : A device, available in two sizes, designed to grip the head of the loose silver point. Silver Point Removal

35. After the silver point is removed, it is important that subsequent instrumentation procedures be performed in a crown-down manner to minimize extrusion of the silver corrosion products into the peri-radicular tissues to decrease the occurrence of painful acute flare-ups. Occasionally, the apical portion of a silver point will separate upon the removal attempt. If it cannot be bypassed or removed, then the case should be completed and followed carefully. Apical surgery or extraction could be necessary in the future. Silver Point Removal

36. Removal of mineral trioxide aggregate Since MTA also sets hard, removal may be difficult if not impossible. At present, there are no solvents available for dissolving MTA. Boutsioukis et al. 2008 evaluated the ability to remove MTA root fillings using ultrasound and rotary NiTi files. The teeth were placed into two experimental groups and MTA was placed with a lentulo spiral filler into the entire length of the canal. In one group, a gutta-percha cone was also inserted to within 2mm of the working length to facilitate re-treatment. When it came to removal, rotary NiTi instruments were unable to penetrate the MTA and could only access the canal if there was gutta-percha present. A combination of rotary NiTi files and ultrasonic instruments was more effective than rotary instruments alone. However, remnants of MTA were detected in all of the re-treated canals. In this study, only teeth with straight roots were used. There is currently no literature on the removal of MTA from curved canals; this is likely to be a very challenging and risky procedure. Boutsioukis C, Noula G, Lambrianidis T. Ex vivo study of the efficiency of two techniques for the removal of Mineral Trioxide Aggregate used as a root canal filling material. J Endod 2008.

37. Assessment of Root Canal Filling Removal Effectiveness Using Micro–computed Tomography: A Systematic Review Aim: This systematic review aims to discuss the effectiveness of different instrumentation procedures in removing root-canal filling materials assessed by micro-computed tomography. Methods: An electronic search in PubMed and major endodontic journals was conducted using appropriate key words to identify investigations that examined the effectiveness of obturation material removal assessed by microcomputed tomography. Conclusions: The application of different instrumentation protocols can effectively, but not completely, remove the filling materials from the root canal system. Only hand instrumentation was not associated with iatrogenic errors. Reciprocating and rotary systems exhibited similar abilities in removing root filling material. Retreatment files performed similarly to conventional ones. Solvents enhanced penetration of files but hindered cleaning of the root canal. The role of irrigant agitation was determined as controversial. Rossi-Fedele et al. 2017

38. Procedural complications and risks The main risks of complications when removing remaining root filling materials include perforation, blockages, loss of working length, ledging, and fracture of the removal instrument. Rotary NiTi files are prone to fracture in certain circumstances, but the incidence may be reduced in experienced hands and when care is exercised. However, there is a lack of evidence that any type of rotary file, landed or non-landed, end-cutting or safe-ended, is associated with a higher risk of complications. Apical extrusion of material: The apical extrusion of material during re-treatment may, potentially, cause an untoward, sometimes acute, flare-up. Time taken to remove root fillings: Re-treatment is more time-consuming compared with initial root canal treatment. More efficient and more rapid techniques for removal of root filling materials would be an advantage.

39. Thanks for listening Ibrahim Bayram