This paper was written to detail, with clinical rationale, the various steps in orthograde first time endodontic treatment of adult teeth with closed apices. The steps detailed are principle driven and will work with virtually any rotary nickel titanium (RNT) instrumentation system. The above notwithstanding, this article describes the use of Twisted Files* (TF) and RealSeal* obturation (with master cones and RealSeal One Bonded Obturators*) to achieve these principle driven goals. These materials are detailed because we believe they are the state of the art RNT and obturation choices on the market today.
The instrumentation and obturation sequences provided will work with virtually any canal complexity (curvature, calcification, dentin hardness), length and tooth type (molar, anterior, etc). The recommended sequence assumes:
• that the medical and dental history have been reviewed.
• the tooth is restorable and peridontally sound.
• percussion, palpation, mobility and probings have been determined for the offending tooth and optimally all of the teeth in the quadrant.
• radiographically, 2-3 images of the suspected tooth are taken to three dimensionally map (to the greatest degree possible) the anatomy of the tooth requiring treatment.
• the patient’s chief complaint has been reproduced. If the patient reports lingering pain to cold beverages, the clinician should subject all teeth in the quadrant to an ice test to determine which tooth gives an outlying response relative to the others.
• the diagnosis is correct, the correct tooth has been identified and that the patient has an odontogenic problem that will be resolved by endodontic therapy.
• the patient has been informed of the nature of the procedure, risks and treatment alternatives.
• all of the patient’s questions have been answered.
• the patient has given informed consent after 2 and 3 above.
• the rubber dam is always used.
• lighting and magnification are used. At a minimum, loupes should be employed, optimally with a light source. One excellent option in loupes is the Class IV HiRes (Orascoptic, Middleton, WI, USA) worn in some clinical circumstances by one of the authors (RM). Optimally, the surgical operating microscope provides unparalleled visualization at much higher powers (Global Surgical, St. Louis, MO, USA) than loupes.
In addition to the requirements above, ideal canal preparation requires that the:
• canal remains in its original position.
• minor constriction (MC) of the apical foramen is left at its original position and size.
• final preparation is a tapered funnel from orifice to apex with narrowing cross sectional diameters.
• canal is prepared to an optimal taper that maximizes irrigation and obturation hydraulics. Inherent in this recommendation is that the final prepared canal is proportionally tapered so as not to predispose the root to strip perforation or long-term risk of vertical fracture through excessive dentin removal.
These goals are sought-after irrespective of the instruments used for canal preparation. Summarizing the instrumentation sequence that is detailed below, straight-line access is followed by removal of the cervical dentinal triangle (CDT). Orifice shaping allows unrestricted access for precurved hand K files to be inserted which are used to achieve apical patency Apical patency is defined here as the ability to easily and reproducibly place a small hand K file through the MC. A glide path is prepared after apical patency is achieved (the canal is enlarged from its initial minimum diameter to the size of a #15 hand K file). Once a glide path is prepared, RNT canal enlargement commences.
Canal preparation is performed “crown down” meaning that the canal is prepared from the crown to the apex. Crown down instrumentation means that RNT files are used from larger tapers and tip sizes to smaller. Such a sequence will allow each smaller taper or tip size to progress further apically relative to the file that preceded it. Once the final taper of the canal is prepared and the first RNT file reaches the apex, the master apical diameter (MAD) is prepared working from smaller tip sizes to larger with files of lesser taper than the taper that the final prepared canal. In other words, if the canal is prepared to a .08 final taper (as described below) and a #25 tip size, creation of the MAD is carried out sequentially with .06/30, .06/35, .04/40 sized RNT instruments.
The goals of endodontic obturation are to three dimensionally fill the prepared canal space with a biocompatible material that seals off the canal from the oral environment and prevents migration of bacteria along the canal. Inherent in the statement above is the requirement that the material be easily retreated, biocompatible, readily available, non toxic, non mutagenic, non allergenic, cost effective, able to be thermosoftened and compacted, have low shrinkage upon cooling, have moderate flexibility (plasticity) among other attributes. Obturation techniques are discussed below.
Attain profound anesthesia. Anesthesia should be tested before access begins. If for example, the patient has sensitivity to cold, the tooth should be challenged to cold. If the tooth is sensitive to chewing, the tooth should certainly be given a percussion test to assure that that the tooth is asymptomatic before access.
Determine an estimated working length (EWL) from the preoperative radiographs. This estimated length is usually accurate to within 1 mm of true working length (TWL).
Apply the rubber dam. It is optimal to clamp the tooth behind the one being accessed and a piece of floss should be attached to the rubber dam clamp.
Make straight-line access. All orifices should be visible in one mirror view of the tooth.
If the vital pulp tissue is evident in the pulp chamber, a viscous EDTA gel like Slick Gel* should be inserted to fill the chamber. Slick Gel is a viscous EDTA gel that is used to hold the pulp in suspension and help prevent the pulp from being pushed apically once canal preparation commences. Doing so can help eliminate blockages, canal transportation and other iatrogenic events.
Rotating at 500 rpm, insert the .08/25 TF and enter it approximately 3 mm into each canal orifice. This action creates an easily accessible opening into which the succeeding instruments can be inserted. Alternatively, a RNT file orifice opener can be used, depending on its taper. Generally, a .08 taper RNT orifice opener is adequate for all canals. The use of Gates Glidden drills is discouraged due to their propensity to screw into the canal and fracture at their tips. In addition, it is inherently challenging to prepare a continuous canal taper with their use.
The canal is irrigated. While clinical opinions differ, one proven method based in the literature is for vital cases to be irrigated with full strength (non diluted) sodium hypochlorite and non-vital cases to be irrigated with 2.0% Chlorhexidine with side vented needles. These solutions are heated before use. Irrigation is copious and an average molar receiving approximately 100-150 CC. 17% liquid EDTA (SmearClear*) is alternated approximately every 3-4 irrigations of the primary bactericidal irrigant. Such alternation of irrigants acts helps clear the smear layer as it forms and allows greater irrigant penetration into the dentinal tubules.
Ideally, the canal is irrigated with the chosen bactericidal irrigant after every RNT insertion in the sequence that follows. Neglect of this step leads to enhanced possibilities of canal blockage and file breakage.
Using the .08/25 TF as an orifice opener, the file is brushed up and away from the furcation toward the thickest wall of dentin. Such an action removes the CDT. This motion will minimize
the possibility of strip perforation. Removal of the CDT reduces the torsion and cyclic fatigue that subsequent instruments will encounter.
After shaping the orifice, a precurved #10 hand K file is inserted apically to determine if the canal is easily negotiable. This precurvature is approximately 30 degrees and placed at the apical 3-4 mm of the file. If the #10 hand K file will not easily advance to the EWL, a #8 hand K file should be inserted. If the #8 hand K file will not easily negotiate to the EWL, the #6 should be inserted instead. If the #6 hand K file does not initially reach the EWL, the precurved file is inserted with multiple orientations until it does. If all attempts to achieve apical patency have failed, the tooth should either be referred or instrumented, irrigated and obturated to the apical level negotiated. Caution and clinical judgment are advised.
Once the first hand K file reaches the EWL, the canal is dried and an electronic apex locator reading is taken.
Working from the first hand K file that reaches the TWL, the canal is enlarged with hand K files until a #15 hand K file spins freely at TWL. This creates a glide path to allow RNT canal enlargement. RNT files are not inserted (beyond the 3 MM of orifice shaping performed previously) until the glide path is created.
To shape the body of the canal and shape the final prepared taper (below the orifice), the .08/25 TF is inserted into the canal with gentle pressure in a single continuous and controlled motion that lasts 2-3 seconds and is withdrawn. In a canal of mild to moderate complexity, this will allow progression of the .08/25 TF to approximately mid root or further apically in the first insertion.
After this first insertion, the canal is irrigated and recapitulated (a hand K file-#6, 8 or 10) is taken to the TWL to assure that the canal is not blocked).
If the .08/25 TF will allow further apical insertion without undue pressure, it is inserted again to resistance. If not, the .06/25 TF is inserted until resistance is encountered.
Using a single .08/25 TF (or alternating between the .08/25 TF and .06/25 TF in a crown down manner), after approximately 3-4 insertions, TF should reach the apex. In a larger canal (the palatal canal of an upper molar or the mesial root of a lower molar), the .08/25 TF is chosen as the final canal taper. In more complex canals, the .06/25 TF is taken to the apex to prepare the final canal taper. In highly complex roots, more TF insertions may be necessary than the 3-4 listed here.
An electronic apex locator reading is taken when the first TF files reaches the TWL.
Once the .08/25 TF and/or .06/25 TF is taken to the apex, the MAD should be prepared. The .06/30 TF, .06/35 TF are inserted to the TWL after the .08/25 TF reaches the TWL. If the clinician wishes to prepare a larger MAD beyond a #35, the .04/40 TF and/or .04/50 TF are inserted in succession. An electronic apex locator reading is taken again when the last TF file is used to the TWL.
After the final bactericidal irrigation, the canal is irrigated with SmearClear* to remove the smear layer and optimize boned obturation (described below), rinsed with distilled water and dried.
Irrigation should ideally be activated. A wide variety of means to activate irrigation are available clinically. These range from mechanical agitation of irrigant solutions up to ultrasonic irrigation. A comprehensive discussion of activation in irrigation is beyond the scope of this paper. In brief though, the greater the degree of activation (be that activation mechanical, sonic, ultrasonic, negative pressure, etc), the cleaner the resulting canal relative to using a passive syringe and needle irrigation.
After canal preparation and final irrigation, if the canal is obturated with a master cone, the .06/20 RealSeal* bonded obturation master cones can be used (bonded obturation is discussed below) easily and efficiently to provide cone fit before final obturation. This cone is universal, in that for the vast majority of clinical cases, the cone can be trimmed to fit the preparation with tugback (defined below).
Master cones increase in diameter according to their taper. Specifically, the .06/20 cone is .2 mm (ISO #20) at its tip. It is .26 mm 1 mm back from its tip, .32 mm 2 mm back from its tip, etc. The number of mm required to provide cone fit is trimmed off the end of the master cone to achieve tugback at the TWL. Specifically, if a #50 MAD is prepared with TF, 5 mm would be trimmed off of the .06/20 RealSeal master cone. 5 mm back from the tip of a .06/20 RealSeal master cone, the cone is .5 mm (ISO #50). The same mathematics governs the use of .04 tapered gutta percha master cones with regard to taper and tip size.
Evidence exists in the endodontic literature that gutta percha degrades in the root canal system over time.1 In addition, gutta percha must be protected with an adequate coronal seal to make it clinically effective. Unprotected long enough, gutta percha will allow the migration of bacteria from orifice to apex. As a result, the importance of coronal seal cannot be overemphasized. Providing an adequate coronal seal is correlated in the endodontic literature with clinical success for this reason.2-5
RS has been described as “a thermoplastic synthetic resin material based on the polymers of polyester and contains a difunctional methacrylate resin, bioactive glass and radio opaque fillers. RS sealer contains UDMA, PEGDMA, EBPADMA and BisGMA resins, silane treated barium borosilicate glasses, barium sulfate, silica, calcium hydroxide, bismuth oxychloride with amines, peroxide, photo initiator, stabilizers and pigment. RS Primer is an acidic monomer solution in water. RS is non-toxic, FDA approved and non mutagenic. With its radio opaque fillers, RS is a highly radio opaque material. The sealer is resorbable.”6
RealSeal bonded obturation has been shown in the endodontic scientific literature in vitro and in vivo to reduce bacterial leakage, a goal which is consistent with improving long term clinical success. Clinically, RealSeal is used and handles almost exactly like gutta percha. The bonded obturation that results from using RealSeal is not a proven monoblock, it does not strengthen roots against vertical fracture (any more or less than gutta percha) nor is the bond a particularly strong one. These issues aside, the evidence for its clinical biocompatibility and resistance to coronal leakage relative to gutta percha is persuasive. Clinical success with RealSeal is equal to or greater than that with gutta percha, but no worse.7-19
RealSeal technology is available in master cone and in a carrier based form (RealSeal One Bonded Obturators*). While the smear layer should arguably be removed when using gutta percha, removing the smear layer is essential to create a bond with RealSeal.
A correct master cone fit exhibits “tugback.” Tugback means that the master cone resists coronal displacement when fully seated. To achieve tugback, the master cone must have intimate contact only in the apical 3-4 mm of the canal and not be bound higher up in the canal. Achievement of tugback assures the clinician that the master cone will not move apically once downpacked and as a result, will minimize extrusion the obturation material and the sealer. If desired, a cone fit radiograph can be taken to verify the TWL and anticipated obturation.
RealSeal sealer is placed in the canal. RealSeal sealer is a self-etching sealer. Enough sealer to lightly coat the canal walls is adequate, it is unnecessary to fill the entire canal with sealer. Filling the entire canal with sealer and down packing a cone only extrudes unnecessary amounts of sealer apically and increase chances of postoperative inflammation. Any means to introduce sealer into canal with minimal extrusion is acceptable. The use of lentulo spirals is discouraged as these instruments can separate and are challenging
to remove.
Obturation commences, be that lateral condensation, single cone obturation, SystemB technique, vertical compaction technique or another master cone based technique. In the absence of the means to provide a warm vertical obturation (vertical compaction technique, SystemB technique, lateral vertical combinations), lateral condensation or single cone techniques are clinically acceptable. The authors favor the use of SystemB technique delivered via the Elements Obturation Unit.* A description of SystemB technique is provided in exhaustive detail in the July 2004 issue of Oral Health, available online at: http://www.oralhealthjournal.com/issues/ISarticle.asp?aid=1000148863.
Alternatively, if the clinician is using a RealSeal One Bonded Obturator (RS1) (or other warm carrier based techniques) after the canal is dried, a “verifier” is placed to the TWL. The verifier that fits passively to length determines the correct obturator (carrier) size for the prepared canal. The RS1 (or warm carrier based device) is placed into an oven and heated according to the programmed settings. After the appropriate heating time, the RS1 is inserted in 6-10 seconds to the TWL. The motion of insertion is intentional and direct. Positioning the patient’s head so that the canal can be reached as easily as possible improves the fluidity of insertion. The tail of the RS1 (or warm carrier based device) is cut off at the orifice level.
A coronal seal, in the form of a build up, is placed under the rubber dam and the occlusion generally reduced depending on the coronal restorations and precise clinical indications. Posts are indicated only when inadequate tooth structure is present to retain the build up. Use of a flowable composite build up is efficient and relatively simple under the rubber dam at the conclusion of endodontic therapy as the material can be easily introduced into the chamber to fill the access and rebuild the tooth’s contours before final restoration. One author (RM) uses Maxcem Elite, a self-etching and self-adhesive composite (Kerr, Orange, CA, USA) as a build up material. As mentioned above, the placement of an early and adequate coronal seal is correlated with enhanced clinical success in the endodontic literature.
Post op instructions are given and any needed medications are prescribed.
A final coronal restoration (crown or bridge) is placed as needed at another appointment.
Recall appointments are carried out ideally at 6 months and 2 years.
A clinically relevant sequence for orthograde first time orthograde endodontic treatment has been presented. Emphasis has been placed on performing the suggested steps in a sequence that build upon on another to minimize iatrogenic events and improve the quality of three dimensional cleaning, shaping and obturation. We welcome your feedback. OH
*SybronEndo (Orange, CA, USA)
Dr. Mounce is the author of the non-fiction book Dead Stuck, “one man’s stories of adventure, parenting, and marriage told without heaping platitudes of political correctness.” Pacific Sky Publishing. DeadStuck.com
Dr. Mounce lectures globally and is widely published. He is in private practice in Endodontics in Vancouver, WA, USA.
Dr. Gary Glassman graduated from the University of Toronto, Faculty of Dentistry in 1984 and is a graduate of the Endodontology Program at Temple University in1987. He has been on staff at the University of Toronto, Faculty of Dentistry in the graduate department of endodontics. Gary is a fellow of the Royal College of Dentists of Canada, and the endodontic editor of Oral Health dental journal. He maintains a private practice, Endodontic Specialists in Toronto, Ontario, Canada. He can be reached through his website www.rootcanals.ca
Oral Health welcomes this original article.
1. C. Maniglia-Ferreira, et al. Degradation of trans-polyisoprene over time following the analysis of root fillings removed during conventional retreatment. Int Endod J. 2007 Jan;40(1):25-30.
2. Lazarski, et al. Epidemiological evaluation of the outcomes of nonsurgical root canal treatment in a large cohort of insured dental patients. JOE 2001 Dec;27(12):791-6.
3. Salehrabi R, et al Endodontic treatment outcomes in a large patient population in the USA: an epidemiological study. JOE 2004, Dec;30(12):846-50.
4. Tilashalski, et al Root canal treatment in a population-based adult sample: status of teeth after endodontic treatment. JOE 2004, Aug;30(8):577-81.
5. Aquilino, et al. Relationship between crown placement and the survival of endodontically treated teeth. JPD 2002, Mar;87(3):256-63.
6. Mounce RE, Glassman, G, Bonded Endodontic Obturation, Another Quantum Leap Forward for Endodontics, Oral Heath Canada, July 2004, p 13-22.
7. Silveira, et al Negative influence of continuous wave technique on apical sealing of the root canal system with Resilon. J Oral Sci June 2007 Jun;49(2):121-8.
8. Bodrumlu, et al Apical leakage of Resilon obturation material J Contemp Dent Pract. Sept 2006 2006 Sep 1;7(4):45-52.
9. Tunga U, Bodrumlu E. Assessment of the sealing ability of a new root canal obturation material. J Endod. 2006 Sep;32(9):876-8.
10. Aptekar, et al Comparative analysis of microleakage and seal for 2 obturation materials: Resilon/Epiphany and gutta-percha. J Can Dent April 2006 Apr;72(3):245.
11. Stratton, et al A fluid filtration comparison of gutta-percha versus Resilon, a new soft resin endodontic obturation system. J Endod. 2006 Jul;32(7):642-5.
12. Leonardo MR, et al. Root canal adhesive filling in dogs’ teeth with or without coronal restoration: a histopathological evaluation. J Endod. 2007 Nov;33(11):1299-303.
13. Shipper G, et al. Periapical inflammation after coronal microbial inoculation of dog roots filled with gutta-percha or resilon. J Endod. 2005 Feb;31(2):91-6.
14. Two- and four-year outcome of biologically-based treatment protocol of endodontically-treated teeth filled with Resilon.
Prospective outcome of endodontic treatment performed in private practice by a single clinican using a standardized protocol with Resilon as the filling material; 2 and 4 year follow-up results. Debelian G. Oslo, Norway. In-manuscript.
15. Cotton, TP, et al. A Retrospective Study Comparing Clinical Outcomes after Obturation with Resilon/Epiphany or Gutta-Percha/Kerr Sealer Volume 34, Issue 7, Pages 789-797 (July 2008).
16. Testarelli L, et al. Sealing ability of a new carrier-based obturating material. Minerva Stomatol. 2009 May;58(5):217-22.
17. Merdad, et al Short-term cytotoxicity assessment of components of the epiphany resin-percha obturating system by indirect and direct contact millipore filter assays. JOE January 2007 Jan;33(1):24-7.
18. Onay, et al In vivo evaluation of the biocompatibility of a new resin-based obturation system. OOO July 2007 Sep;104(3):e60-6.
19. Key, et al Cytotoxicity of a new root canal filling material on human gingival fibroblasts JOE August 2006 Aug;32(8):756-8.
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