Written by John D. West, DDS, MSD Friday, 31 December 2004 19:00
What does it mean to do great endodontics? The critical distinction of great endodontics means consistency of excellence. This consistency can be measured using a “finishing checklist.”
(1) Mechanical objectives. (The final radiographs demonstrate the achievement of the mechanical objectives).
(2) Appropriate. (The radicular outline form should not be too big and should not be too small. It should be “just right” for the size and shape of each unique root.)
(3) Smooth. (The entire preparation outline form should be smooth from chamber entrance to root canal system terminus. This determinant ensures appropriate obturation hydraulics at each cross-sectional level. Since all portals of exit are potentially significant, achieving smooth walls is key to success.)
(4) Solid. (The No. 1 thing on everyone’s checklist is solid. This is true whether we survey the American Association of Endodontists (AAE), program directors, the scientific advisory board of the AAE, or “valued clinicians.”1
(5) The “4” Dimensional. (Stop obturation material 1 to 2 mm short of the access chamber entrance and make solid restorative transition into the access. Regardless of how the referring doctor restores, this critical step will help protect the obturation material by preventing possible future microleakage.)
In order to have a great result, all 5 parts of the finishing checklist must be met. This is particularly difficult in endodontic retreatment, which is why it can be the ultimate endodontic challenge: a skill within a skill. How do we consistently achieve the checklist in the face of pressures to do otherwise, such as perforations, blocks, ledges, and transportations?
Many dentists have mastered fixed bridge and crown re-moval using the Coronaflex (KaVo) or the WAMkey device (Paris, France). Removal of posts is relatively simple with the proper use of ultrasonics and the Ruddle Post Extractor (DENTSPLY/Tulsa). The key in post removal is, however, to preserve the pre-existing retentive ferrule, which at a minimum is 1.5 mm in height and 1 mm in thickness. It is the facial-lingual ferrule that is the most important to the success of the restoration. Removal of silver cones and gutta-percha is facilitated using ultrasonics, solvents, and rotaries. Removal of pastes is accomplished using Endosolv R for resin pastes and Endosolv E for eugenol-based pastes (Septodont).
Removal of metal gutta-percha carriers is similar to silver cone removal. However, a useful technique is to grasp the carrier with small hemostats and to heat the hemostats with the obturator heater (System B, Sybron Endodontics or the Touch ‘n Heat, Kerr).
Then remove the Thermafil or any other carrier-based device with hemostats heated with the System B or Touch ‘n Heat. Plastic carriers are removed in the same way, but if the carrier is a size 40 or less, then it will not dissolve in traditional endodontic solvents, and a heat carrier or rotary may be needed to facilitate removal. Broken instrument removal is a separate subject, and this skill can be addressed in detail in another article. Again, however, the guideline is to remove the instrument and leave the tooth structure. Do not make a shelf and do not perforate.
The real endodontic challenge comes, however, when disassembly is complete and what remains is a root canal system that has been perforated, blocked, ledged, or transported. What are the essential elements and what is the critical thinking required to solve each of these barriers to success?
|Figure 1a. Pretreatment of post perforation and gutta-percha cone tracing sinus tract.||Figure 1b. Digital radiograph at treatment visit.|
|Figure 1c. Four-year follow-up digital radiograph showing lateral osseous healing. Root canal system was not re-treated.||Figure 1d. Clinical of sinus tract healed.|
The main problems with perforations are (1) the angle of access is not in alignment with the angle of incidence; (2) bleeding; and (3) difficult to compact due to lack of a backstop (Figures 1a and 1b). Prior to MTA (DENTSPLY/Tulsa), time-tested materials such as Calcitite nonresorbable hydroxyapatite bone-grafting material (Calcitek) were used to create perforation barriers to seal against with good long-term results. MTA has further improved results. With the use of microcarriers to place the MTA and then trowel it into the perforation with microspatulas such as the West Nos. 1 and 2 and Nos. 3 and 4 (Sybron Endo-dontics), this material has led to excellent success by many clinicians (Figures 1c and 1d).
|Figure 2a. Anatomy of a “block.”|
What is the anatomy of a block? How are they formed?2 What does the dentist have to think and do in order to predictably “deblock?” When an instrument does not go to length due to a dense collagen or “dentin mud” block, the densest part of the block is the most incisal or coronal. The majority of the apical portion is more “lightly packed” (Figure 2a). The reason for this is found in how the block got there in the first place. It is often there because of lack of restraint by the clinician. First, he or she discovers the instrument just “won’t go.” The very next human reaction is to push. That does not solve it so we push harder. The clinician experiences more frustration and begins to push harder and harder, thinking that this forcing will enable him or her to thrust through the block back to home base.
|Figure 2b. Pretreatment radiograph showing gutta-percha cone tracing to probable lateral portal of exit(s).||Figure 2c. No. 8 file gently touching “dense dentin mud” multiple times in order to disrupt beginning of block.|
A more effective technique is to do exactly the opposite of forcing and trying. If the clinician were to choose to be delicate, patient, and demonstrate extraordinary restraint, then deblocking is predictable and fun. So, I play a game whenever a file does not advance due to a block. I agree with myself, with the patient, and with the dental assistants that I will slide to the block, gently touch it without any intention of going deeper, irrigate and do that 10 times without pushing. We will always go deeper, although it may only be a micron! This enables the clinician to disturb the dense block and then easily navigate to the terminus again (Figures 2b and 2c). A No. 8 file is recommended.
Rules for Deblocking
(1) Remember, the path is still there.
(2) Shake your fingers “loose as a goose.”
(3) Whistle a merry tune.
(4) Irrigate thoroughly with sodium hypochlorite.
(5) Make believe you can do this.
(6) Forget the clock.
(7) Remember the game of restraint, and the promise to slide deeper is the reward.
(8) Use randomizations and not searching.
|Figure 2d. Six-month follow-up radiograph showing osseous healing.||Figure 2e. Sinus tract healing.|
Now, these rules always work, unless they do not! Imagine you have faithfully followed these steps not 10 times, but say 30. When these blocks are so dense, they need a little more persuasion, or, shall we say, encouragement. A useful irrigant at this point is Chemet (Succimer, 150 mg).3 This “compounded strength EDTA” in combination with a No. 20 reamer (preferably carbon) will enable the clinician to “tunnel” through and down almost any dense collagen or dentin block and then successfully clean, shape, and develop obturation hydraulics that enable a 3-D seal and healing (Figures 2d and 2e).
|Figure 3a. Line drawing illustrating ledge.|
|Figure 3b. Line drawing illustrating reduction of ledge enabling cone fit.|
|Figure 3c. Retreatment of mandibular molar does not allow ProTaper Finisher 1 to pass by ledge.|
|Figure 3d. Precurving of ProTaper F1 using cotton pliers or orthodontic pliers.|
|Figure 3e. Now ProTaper F1 manually slides past the shelf and is manually rotated several times. Ledge is easily removed and cone can now fit.|
Ledges are an endodontic clinician’s least favorite friend (Figures 3a and 3b). In addition, one of the fatal flaws of NiTi rotary is when a smooth glide path has not been created before the rotary shaping. Previous techniques required the clinician to precurve a small file or hedstrom, slip around the ledge, and circumferentially file to reduce the ledge sufficiently to allow the gutta-percha cone to go to length. Of course, the outline form was permanently imperfect, and to shape smoothly beyond the ledge was more luck than intention. Precurv-ing a ProTaper F1 (ProTaper, DENTSPLY/Tulsa), sliding past the ledge manually, and then rotating manually for 2 to 4 revolutions can achieve a more effective elimination of ledges (Figures 3c to 3e). These finishers are designed to cut at exactly any spot that prevents its exact shape from being carved. The cone and subsequent 3-D obturation follows.
|Figure 4a. Pretreatment radiograph of endodontic failure.|
|Figure 4b. Line drawing demonstrates sufficient tooth structure to warrant nonsurgical retreatment.|
|Figure 4c. Twenty-year recall.|
|Figure 4d. Line drawing demonstrates insufficient tooth structure to warrant shaping required for vertical compaction obturation.|
|Figure 4e. Pretreatment digital radiograph showing underformed apex and lesion of endodontic origin following pulp necrosis.|
|Figure 4f. MTA apical placement and immediate composite coronal restoration.|
The problem with the torn or “open apex” is there is no capacity to capture the maximum cushion of obturation material and mold it apically. Where there is enough tooth structure to achieve an appropriate, continuously tapering cone, ie, a “super foramen,” simply shape inside, fit the cone, and pack (Figures 4a to 4c). Where there is not enough tooth structure, place an apical barrier with Colecote (Sybron Endo, or Capset calcium sulfate bone-grafting material, Lifecore) and then obturate with sealer and gutta-percha using the Obtura (Obtura/Spartan) or “Calamus” Flow Obturation Delivery Device (DENTSPLY/Tulsa Dental, Figure 4d). A more recent technique is MTA obturation followed by composite restoration (Figures 4e and 4f). No gutta-percha is required.4 This can be a single-visit procedure and particularly useful when a child is noncompliant and whose visits are episodic.
Like all endodontic challenges, perforations, blocks, ledges, and transportations are also opportunities. They are opportunities for all of us to perfect our clinical artistry further and take these breakdowns and turn them into successful breakthroughs.
1. West JD. Finishing: the essence of exceptional endodontics. Dent Today. Mar 2001;20:36-41.
2. West JD. Cleaning and shaping the root canal system. In: Cohen S, Burns RC. Pathways of the Pulp. 7th ed. St Louis, Mo: Mosby; 1998:242.
3. Hottel TL, el-Rafai NY, Jones JJ. A comparison of the effects of three chelating agents on the root canals of extracted human teeth. J Endod. 1999;25:716-717.
4. Torabinejad M, Chivian N. Clinical applications of mineral trioxide aggregate. J Endod. 1999;25:197-205.
Disclosure: Dr. West maintains a royalty position with ProTaper Rotary Files, DENTSPLY/Tulsa.
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