Written by Richard E. Mounce, DDS Monday, 31 August 2009 19:00
Knowing when to treat an endodontic case and when to refer is an invaluable clinical skill. There is one best chance to get an excellent final result―the first time the tooth is entered. Much like an extraction that is referred midtreatment with an open flap and a root tip, referring a tooth during the middle of a root canal procedure is rarely satisfactory for any of the parties involved. It most often leaves the patient with lost trust in the clinician who started the procedure and yet, in the end, could not finish.
Making clinical decisions about which patients and teeth should be treated, and which should be referred, ultimately hinges on the following fundamental question: Am I the best clinician to treat this patient at this moment; given the skills, time, equipment that I possess, and the patient’s needs? If the answer is yes, the treatment should be started and if no, the patient should be referred. Inherent in this question is an adequate case assessment with regard to the risks posed by the tooth and any special needs of the patient. Starting a tooth with the belief that it can always be referred later is dangerous because very rarely is the tooth/patient in better condition by a midtreatment referral.
There are myriad reasons for referral. Some patients may have special needs that make even the simplest root canal a challenge (limited opening, dental anxiety, medical considerations that alter their care, etc). Alternatively, cooperative patients, and those without special needs, may possess a tooth of extreme difficulty and need advanced materials and techniques. Some especially difficult teeth may have both factors working in tandem; a challenging tooth along with challenging patient management. In any event, if the general practitioner is honest with themselves after evaluating the patient and tooth properly, as to whether the case requires a specialist or not, given the criterion above, will be a relatively simple decision.
CLINICAL EXAMINATION OF THE CASE DISCUSSED
Figure 1. The clinical case before the initial access.
Figure 2. The clinical case after access and at the time of referral.
The clinical case described in this article addresses a tooth of severe difficulty that was referred mid treatment because one of the canals was blocked after access. Its management is discussed from a clinical viewpoint with an eye toward addressing the risk factors that were initially present and how these factors were managed after referral.
STRATEGIES NEEDED TO PREVENT IATROGENIC OUTCOMES
Figure 3. The Twisted File (SybronEndo).
Figure 4. The clinical case after completion.
|Figure 5. RealSeal (SybronEndo) bonded obturation material.|
This tooth was ideally treated with a surgical operating microscope (SOM [Global Surgical]). The SOM brings many clinical advantages to treatment of all types, endodontic and otherwise. In my hands, the SOM is used for every patient, every tooth, every day, from the initial access through the completion of the build-up. My operatories do not have overhead lights because the SOM is also my overhead light. Especially for cases with this level of difficulty, the SOM is an invaluable diagnostic tool before treatment providing the means to guide the course of treatment because canal shaping and obturation takes place in full view of the clinician.
The SOM is especially valuable in canal location. In this particular case, it was used to confirm that there was no third mesial canal and/or a second canal in the distal root, ie, that all the canals had been located. Viewing the tooth through the SOM could also alert the clinician to the possibility of a furcal floor or vertical root fracture. The widened periodontal ligament at the cervical level of the mesial root in the Figures 1 and 2, give rise to the possibility that a fracture might have occurred and not yet become fully manifest radiographically. No fractures were observed upon access with the SOM after access.
Access refinement is vitally important to allow unfettered tactile control in the apical third. Ideal straight-line access and cervical dentinal triangle removal are the platform on which the middle third and apical shaping are based. Ideal management of the second curvature at the apex of the mesial root depends wholly on the quality of the coronal access. If access is compromised, or restrictive dentin is not removed in the coronal portion of the root, the clinician doesn’t have tactile control of the files at their tips in the apical third risking debris blockage, ledging, and fracture.
In this clinical case, the orifices were refined with the Twisted File (TF [SybronEndo]) (Figure 3) in the .08 taper in all canals. The access was copiously irrigated in order to remove any debris from the chamber floor as it was formed. Orifice enlargement and removal of the cervical dentinal triangle was performed with an upward brush stroke away from the furcation with the TF to minimize any possibilities of perforation. The .08 TF was chosen for this task because .08 was also the ideal master apical taper. TF is able to create larger tapers throughout the length of the root relative to many other RNT file systems that are manufactured by grinding. The .08 taper was chosen considering the risks of instrument fracture as well as the risk of midroot perforation in this challenging root.
It is advised that the clinician consider the final taper (master apical taper) that will be prepared as well as the master apical diameter and be confident that their chosen system will allow the preparation of both these dimensions. For clinicians using ground RNT instruments, the master apical taper for this clinical case would realistically be .06 taper and not .08 taper. Going into the case the clinician would not know specifically what the master apical diameter should be, that said, once the canal is prepared to a .08 taper throughout its length, the clinician can determine the initial diameter of the minor constriction (MC) (by gauging the canal) and then adjust the master apical diameter from that level.
Since the clinician who had started the case had removed dentin in the coronal and apparently into the middle third of the root, care was taken to look for a perforation upon entry into the canal. If the root wall was already thin toward the furcation, using too large of a taper could create an overt perforation. Even if such a perforation were not created, removing too much dentin unnecessarily would leave the root vulnerable to vertical fracture later after the completion of treatment.
TREATMENT STEPS UNDERTAKEN IN THIS CLINICAL CASE
The procedure was explained to the patient, the alternatives were discussed (extraction) the risks of treatment explained (separated instrument and perforation risk) and their questions answered. The patient consented to have treatment and the case commenced.
Sequential management of this case through each stage of this cases progression is essential. Treatment staging requires straight line access, orifice location, cervical dentinal triangle removal, shaping of the coronal third, middle third, and finally the apical third, followed by obturation and coronal seal.
The patient was anesthetized with a combination of Articaine and Marcaine by infiltration and inferior alveolar block, and then a rubber dam was applied. Access was made and expanded slightly to allow straight-line access into the mesial canals. The initial access upon referral did not allow a hand or RNT file to progress into the orifice of the mesial roots without deflecting off of the access walls. At the time of access, it was noted that the orifices of all canals were relatively small, especially in the mesial canals. This lack of initial size is relevant because it explains in part, the challenge of negotiating the apical curvatures of the mesial root. An inadequate orifice size diminishes the irrigation of the mesial roots as well as restricts the tactile control of hand files and RNT files further apically.
After refinement of the access, the first goal was to enlarge the coronal 3 to 4 mm of the canal to allow apical patency to be achieved. The .08 TF was inserted into the orifice of all canals to provide optimal hand K file (HKF) negotiation. The initial estimated working length was 23 mm. An adequate supply of No. 6 and No. 8 HKF were available for negotiation of the canals. No. 6 HKF was precurved using an EndoBender pliers (SybronEndo). Significant time was spent using No. 6 HKF to establish patency. Multiple insertions of precurved No. 6 HKF instruments were directed into different portions of the apical root anatomy. In both of the mesial canals there was significant resistance to apical movement of the HKF with the mesial lingual canal demonstrating a complete blockage near the apex. In the mesial buccal the tactile perception was that the canal was ledged and needed to be bypassed and the ledge rubbed out. In the mesial lingual the tactile perception was that the canal was blocked with debris. HKF were not forced, but rather finessed, into the portions of the apical root anatomy in which progression could be made. After numerous attempts, the canals were patent to the estimated working length of 23 mm and a tangible pop was detected at the apex of the root in each canal.
Once the estimated working length was reached, the electronic apex locator was put on each HKF and the first determination of the true working length (TWL) made. The MC was used as the location of the TWL in this treatment. All instrumentation, irrigation and obturation were taken to the MC with nothing beyond except patency files.
After patency was achieved, the No. 6 HKF pathway was enlarged to that of a No. 8 HKF using the M4 Safety Reciprocating Handpiece (SybronEndo). The M4 reciprocates HKF 30° clockwise and 30° counter clockwise. It mimics the manual use of HKF. Reciprocation, performed with the M4 safety handpiece, takes place with a vertical movement of 1 to 3 mm, gently and slowly for approximately 30 seconds. As time progresses during reciprocation, the HKF meets less resistance and moves vertically more easily as the canal is enlarged. The M4 safety handpiece is used with an electric motor possessing an E type coupling at 900 rpm at the 18:1 setting. Reciprocating a No. 6 HKF can enlarge a canal to the size of a No. 8 HKF, reciprocating a No. 8 HKF can enlarge a canal to the size of a No. 10 HKF, etc. After the canals in this clinical case were reciprocated by the No. 10 HKF (because the canal is effectively the size of a No. 15 HKF), the tooth was ready for RNT enlargement.
TF was chosen because relative to other RNT, it allows the creation of greater tapers to the apex, can reach the apex in fewer insertions, is extremely flexible, does not possess areas of metal roll over and micro cracking at its surface from manufacture (as do some ground RNT files) and has unsurpassed fracture resistance. It is a complete system with files available in the following tapers and tip sizes: .12/25, .10/25, .08/25, .06/25/30/35, and .04/25/40/50.
The distal root bled profusely after the first insertion of a hand K file into the apical region of the canal. From the initial radiographic images it was determined that the apex of the distal root was unlikely to have suffered an iatrogenic event. The bleeding was interpreted as having occurred as a result of pulp tissue that might have been left in the canal as a result of the initial attempted treatment. Once a No. 15 HKF reached the apex of the distal root, the canal was instrumented with TF, as were the mesial canals. It was expected that once the pulp tissue was removed from the distal root, the excessive bleeding would stop, which it did.
The TWL was determined to be 22 mm electronically in all canals, despite the mesial roots appearing shorter than the distal roots radiographically. Given the complexity of the mesial root, it was decided to create a smaller taper first and then adjust the taper to a larger master apical taper. In the mesial roots the .06/25 TF was inserted and in 4 individual motions, the canal was shaped to the MC. The rubber stops were removed from the TF in order to read the laser markings that are present near the head of the files. The .06/25 TF was able to reach the apex of the distal root in 2 insertions. The .08/25 TF was inserted next and reached the apex of all 3 canals in 2 insertions.
Had this clinical case been less complex, potentially, the entire case could have been shaped crown down using larger tapers to smaller (inherently crown down). The double curvature, degree of root fluting, the fact that the case had been accessed before, all argued for caution and initial creation of a smaller taper. Insertion of TF was passive and taken to resistance and the file removed. I rotate TF at 900 rpm with the torque control off. Each insertion takes 2 to 3 seconds and the file is turning on entry and the file removed upon resistance. Of the 2 significant curvatures present in the mesial root the apical curvature is the more likely to cause iatrogenic potential. It is important to insert TF to the MC and not further. In other words, at all costs, the clinician needs to avoid locking the tip of the file at the apex or taking the RNT beyond the MC. Doing so can lead to apical perforation or file breakage, either of which is an event that will leave significant uncleaned and unfiled space apically and predispose the tooth to failure.
After the canal was prepared to the initial diameter of a No. 25, the master apical diameter was enhanced to a No. 35 in the mesial and a No. 40 at the distal. TF was used step back from .06/30, .06/35 and .04/40 in the 3 canals in this order. The smaller taper of the .06 and .04 TF fit easily inside the larger taper of the .08 master apical taper (the largest taper taken to the apex). It is especially important, irrespective of the RNT system used, that the clinician irrigate and recapitulate after every insertion. Recapitulation was preformed with a .10 HKF and was designed to assure that the canal path was patent.
Working length was remeasured and assured at several junctures in the treatment; after the first TF reached the TWL, and after the last TF reached the TW. A bleeding point was taken with paper points prior to obturation to assure that the canals were open, patent, and negotiable as well as to reconfirm the position of the MC/TWL.
It is noteworthy that the orifice and coronal third of the distal canal was not made bigger than that shown in Figure 4. While it could have been made larger, there was little if any clinical indication to do so. The chosen size was both appropriate to open the more apical levels of the canal to cleaning, shaping, and obturation but also creates a minimal risk of future vertical root fracture given that excessive dentin was not removed in preparation and a post was not indicated. This conservatism should be compared to the case where the removal of dentin at the coronal third is excessive (from using orifice openers and Gates Glidden Drills that are too large for the root form) and represents a significant risk for a future vertical root fracture.
The tooth was irrigated throughout the procedure with sodium hypochlorite that had been heated first in a water bath. The final irrigation was performed with a liquid EDTA solution, SmearClear (SybronEndo) to remove the smear layer. Obturation was performed with RealSeal (SybronEndo) (Figure 5), via the System B technique and the Elements Obturation unit (SybronEndo). Cone fit was achieved using .06/20 RealSeal cones that were trimmed at their ends until the cones had tugback at the TWL. Sealer was placed using the 17 mm NaviTip (Ultradent Products) on the Skini Syringe (Ultradent Products). The coronal seal was placed with Maxcem Elite (Kerr) and the tooth was rough prepped for a crown and taken out of occlusion. The tooth retained 2 complete access walls as well as portions of the other 2, hence, no post was indicated.
A clinical case has been presented which discusses the clinical pre- and post-op assessment of a challenging clinical case. Emphasis has been placed on risk assessment as well as prevention of iatrogenic events by achievement and maintenance of apical patency as well as attainment of an ideal master apical taper and diameter.
Disclosure: Dr. Mounce is on the advisory board of SybronEndo and is paid for some aspects of this work, for example, giving lectures.
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