Written by Richard E. Mounce, DDS, and Gary D. Glassman, DDS Friday, 31 October 2008 19:00
Often, the information that clinicians need in making decisions in their clinical cases is not easily found in text-books or in scientific articles. Clinicians regularly send us questions about specific clinical cases; we will share 3 of them in this article. We have made observations from the history and radiographs provided. Each of the clinical cases discussed will illustrate an important clinical principle that will ultimately guide how the treatment might be carried out. These cases are shared with the goal of discussing the clinical ramifications, treatment considerations, and possible options that the clinician has going forward, given the parameters provided.
CASE 1: QUESTION
“I saw this female adult patient with a noncontributory medical history first on January 18, 2008. She had a draining parulis facial to tooth No. 10 with percussion sensitivity on that tooth. Tooth No. 10 tested necrotic and slightly mobile. A pulpectomy was performed that day. She returned on February 22, 2008 with the drainage completely healed and the mobility decreased. Treatment was completed. She returned on April 18, 2008 for a hygiene visit, at which time it was found that the drainage had resumed. I am attaching the films from the 3 visits. What is your opinion?” (Only 2 films were provided in the clinician’s communication).
CASE 1: ANSWER
It is a positive development that the parulis healed in the 3 weeks noted. It is possible that it will take longer, up to 2 to 3 months in some cases. The fact that it came back is an indication that the treatment was unsuccessful.
While this tooth is an anterior (eg, an upper lateral incisor), and might be considered to be relatively simple by some clinicians, a careful examination of the root reveals several important observations that may influence treatment.
Preoperative Considerations for Case 1
|Figure 1a. Case 1||Figure 1b. Case 1|
Upon careful radiographic examination, the apex looks immature (Figure 1a). Whether this is from trauma, arrested development from the time that the pulp became nonvital, or another etiology, is not entirely clear. In any event, the presence of such an “open” apex will have clear implications for the clinical treatment. First, it would be relatively easy to over-instrument the canal, violate the minor constriction (MC) and extrude obturating material, sealer, and irrigants through the apex. Second, there is a great deal of taper in the coronal two-thirds of this root, and the taper narrows somewhat in the apical third. In essence, the preparation is not continuous throughout its length. The canal is relatively large initially; and as a result, the tooth required relatively little instrumentation after access. The cleanliness derived from its treatment was always destined to be more effective from irrigation than mechanical preparation.
The shape of the apical anatomy makes determination of the true working length somewhat challenging. Radiographically, the minor diameter of the apical foramen appears approximately 2 to 3 mm up the root and this has implications for treatment. Each insertion of a Rotary Ni-Ti (RNT) file will have to be carefully correlated with the incisal reference point. In this clinical case, the final obturation will ideally be made somewhat short of the anatomic apex of the root, given the initial narrowest diameter of the canal.
Choosing the correct taper throughout the entire root, especially in the apical one half, is not entirely straightforward. It is essential that the clinician choose the correct initial taper for the root. While a .12-tapered RNT orifice opener would rather easily engage the coronal third, the clinician should resist the temptation to use such an instrument. Using a .12 orifice opener first will have a tendency to enlarge the coronal third beyond that which is needed, and to make the creation of a continuous taper, from the orifice to apex. The clinician should instead consider using a .10 or .08 instrument such as the Twisted File (TF) (SybronEndo) to the estimated working length. Either of these files could easily shape this entire canal with one instrument to the apical terminus.
Postoperative Considerations for Case 1
The postoperative images have a number of distinctive features, which might guide the future management of this case (Figure 1b). There appears to be some space within the root canal system that is uncleaned and unfilled. Looking to the mesial of the primary filling point, there is a sealer tract; and both sides of the point show a shadow indicating a clinical void. It is noteworthy that this void is likely 360° around the point, and not just to both sides of the point. (It is buccal to lingual, as well as mesial to distal). While such treatment may heal, even with a clinical void, such a void is indicative of less than optimal cleansing, shaping, and obturation.
The junction of the middle third gutta-percha and the apical gutta-percha shows an acute bend to the core filling material. It appears that the obturation is a single-cone filling. The obturation does not appear to have been compacted into the root canal space, and as a result, the quality of the apical seal is in doubt.
It is difficult to make certain conclusions as to the final position of the obturation, but if the electronic apex locator gave this position as the location of the MC and there was confirming evidence in the form of a bleeding point, then the apical termination point is accurate.
Clinical Recommendations for Case 1
Given the fact that the drainage has resumed 3 months after the initial visit, it is advisable to remove the gutta-percha and place calcium hydroxide for one to 3 weeks. If the tooth is asymptomatic after the placement of the calcium hydroxide, the canal can be prepared, ideally to a master apical diameter, which is biologically relevant. Biologically relevant in this context means to determine the initial diameter of the MC by gauging the apex. Gauging would be accomplished by taking a hand K file to the MC. The hand K file that binds at the MC is the initial diameter of the MC. After the canal is gauged, the canal can be prepared to its master apical diameter. For example, if a No. 40 binds at the MC, the canal could be prepared to a No. 55 or 60 RNT file, such as the .04 tapered K3 (SybronEndo); taking the various K3 files in sequence from Nos. 40, 45, 50, and 55, etc. Subsequent obturation would ideally be via a warm vertical condensation technique that would value tugback of a well-fitted master cone to minimize the possibility of extrusion of sealer and obturation material.
CASE 2: QUESTION
|Figure 2. Case 2|
“This patient has had tooth No. 31 treated. The tooth is asymptomatic, but the periapical area is suspicious (Figure 2). Is that a lesion? Alternatively, would you say it is the inferior alveolar nerve canal? The coronal seal has not been intact for some time, probably years. I recently began seeing this patient and told her that this tooth would require a retreatment. Her response? ‘Just extract it then.’ So I told her that we would like to get another look at the x-ray from you to verify that it would need retreatment.”
CASE 2: ANSWER
Preoperative Considerations for Case 2
Cone beam technology would be very helpful to determine the position of the inferior alveolar nerve bundle. Ideally, we would like to see more digital radiographs of this tooth: one radiograph from the mesial, one from the distal, and one from the buccal. If we only had one picture, our assessment is that the radiolucency is both a lesion and the canal. One is superimposed upon the other, with one being more to the buccal and one more to the lingual. If this tooth is to be retained, it is indicated for retreatment as soon as possible.
The primary indication for retreatment is the lack of a coronal seal. Even if this tooth did not have an apparent apical lesion, the lack of a coronal seal indicates that the contents of the canals are contaminated with bacteria. As a result, it is a matter of time before this tooth becomes symptomatic. This tooth has good bone support and an excellent root structure. In addition, there are no periodontal indications for its removal. Significant uncleaned and unfilled space is present in the canal system. It is very possible that there are up to 5 canals present in this tooth. While only this view of this tooth is available for evaluation, it is highly unlikely that this tooth only possessed 2 to 3 canals; given the width of the roots in a mesial to distal direction, and especially considering the amount of dentin that is present at the mesial aspect of the mesial root.
Given the appearance of the obturation to be fairly blunted at the apical extent, it is very possible (and highly likely) that there is significant canal space in the apical 3 to 4 mm. While the radiographic apex is an unreliable landmark for determining the true position of the MC, given the distance of the root canal filling to the radiographic apex, it is unlikely that the apical third of these roots has been adequately cleansed, shaped, and obturated. Several possibilities must be considered; one is that the roots are now blocked with debris from the previous treatment, and that in an attempt to retreat the apical aspect of the canals, the blockage would be made worse. Steps would certainly need to be taken to address these is-sues in retreatment.
Retreatment Technique for Case 2
While retreatment is usually a specialist procedure, it has value to address the technical steps that would be used to prevent blockage of the apical aspect of the tooth, as well as to enlarge the apical third of such a challenging clinical case.
First, irrigation would be copious. Given that this is a retreatment, the irrigant of choice would be 2% chlorhexidine, because of its ability to predictably remove E faecalis from the root canal system. Removal of the gutta-percha from the root canal system in this clinical case would be passive, mechanical, and thermal first—before the use of solvents. An excellent set of instruments to achieve this removal would be the heat source from the Elements Obturation Unit (SybronEndo) using the SystemB (SybronEndo) heat tips. Mechanical means would include the K3 shapers (SybronEndo) and TF (Twisted File [SybronEndo]) in .12 and .10 sizes. Solvents such as chloroform to dissolve the gutta-percha would not be dropped into the canals until the gutta-percha had been removed to the level of the previous apical termination of the filling. Once the bulk of the gutta-percha is removed from the root canal system, the solvents are entered one drop at a time into the chamber. Then, a small hand file is used to gently work the solvent down the canal to dissolve the remaining gutta-percha.
The hand files must be used with several precautions and considerations in mind. The hand K files are precurved with Endo-Bender pliers (SybronEndo) that precurve the hand K file in the apical 3 to 4 mm. The hand files used in the early negotiation of the apical third of this tooth would be small Nos. 6, 8, and 10 files. It is important to make sure that the hand K file used is stiff enough to allow the instrument to break through calcifications and blockages. It is important that the clinician track and negotiate the true canal and not create a ledge. Part of the ability to do this is done by using a hand K file that is long enough to reach the anticipated length of the root. In this case, the root is approximately 23 to 25 mm and the hand K file used should reflect this length but be stiff enough to break through the blockage.
As the hand K file is placed down the root and apical progress is made, the clinician should be aware of the length of the root and attempt to correlate the tactile sensation of the hand file to the resistance of the file; bearing in mind the length of the file inserted and where it is in the canal. Specifically, the clinician anticipates that a tangible “pop” should be felt once passing through the MC. This tangible feeling can be correlated with the reading of an electronic apex locator (Elements Diagnostic Unit [SybronEndo]) to finalize the position of the file relative to the MC.
The aforementioned steps are occurring with a drop of chloroform in the canal to soften the gutta-percha. As the clinician moves down the canal, once there is no further slurry of gutta-percha evident, the clinician should switch from the gutta-percha solvent to 2% chlorhexidine and complete the negotiation of the canal to the MC. Once the canal has been negotiated to the MC, it can be enlarged to an initial diameter of a No. 15 hand K file, which is the creation of a glide path for the subsequent RNT files which will be used.
All of the above presupposes several important conditions: use of the rubber dam; use of the surgical operating microscope (G-6 SOM [Global Surgical]) to have ideal visual and tactile control over the process; straight line coronal access, which makes possible straight line apical access; and removal of the cervical dentinal triangle.
It should be noted that there could be apical drainage upon gaining apical patency. However, it is not likely given the fact that the patient is asymptomatic and there is no reported palpation sensitivity or swelling. In any event, drainage or not, this clinical case would ideally be completed in 2 visits using calcium hydroxide as an interappointment medicament between the visits. Finally, after this tooth is retreated, it is essential to place the coronal seal at the time of treatment.
CASE 3: QUESTION
|Figure 3. Case 3|
“This patient came in today with in-durated swelling on the lower left buccal area for one day. There was no pain intraorally, just on the exterior. A periapical radiograph of tooth No. 18 is attached with what looks like a periadicular lesion around the distal root. RCT was done in 2004. There was no percussion sensitivity or temperature sensitivity. I told her she needed a retreatment of the tooth with you. I am putting her on a 10-day regimen of Pen VK and getting her in to see you in the next 7 to 10 days. Let me know your thoughts.”
CASE 3: ANSWER
Preoperative Considerations for Case 3
Preoperative and radiograhic observations of this tooth include the following: as a matter of managing the clinical swelling, this patient ideally should have an incision and drain-age with the choice of having IV sedation. While the patient could be given antibiotics and observed, such a treatment is not as entirely predictable as an incision and drainage would be. After the swelling was managed and resolved, the tooth is ready to be retreated.
Retreatment and Technical Considerations for Case 3
After the swelling is managed and resolved, the tooth is ready to be retreated. The mesial root canal preparation is ledged. Radiographically, it is clear that the path of the root, and the path of the obturation, do not coincide. In essence, the apical 2 to 4 mm of this root was not negotiated properly. Also, there was no glide path guiding the RNT used to prepare the canal. It is not at all predictable (or certain) that the true canal path can be recaptured. While it is possible that it could be recaptured, the patient should still be informed that surgery might be necessary. This is especially the case if, after all of the needed techniques are applied, the canal cannot be ideally cleaned, shaped, and obturated. Significant time and effort will be required to achieve patency after the removal of the warm carrier-based product used to obturate this canal.
It is highly likely that coronal microleakage is present. While not as obvious as in case 2 presented previously, there are several very strong clues indicating the presence of coronal leakage. First, the mesial margin still has sealer from the cementation of the crown, and the crown appears to have a slight discrepancy relative to the tooth structure. As a result, the margin cannot be assumed to be sealed.
It appears that there may be gutta-percha in the chamber. In any event, whether it is gutta-percha or composite, there are voids present. Empirically, almost without exception, access through crowns leads to clear evidence of coronal microleakage under crowns during retreatment. Said differently, having retreated many thousands of teeth between us, it is our empirical observation that it is extremely rare to access a crown which does not show clear evidence of coronal leakage under the SOM. After retreatment, this crown needs to be remade and the marginal discrepancy on the mesial resolved definitively.
The serrations present radiographically quite clearly distinguish these obturators as an early version of the product type. Removal of obturators with metal carriers (as opposed to plastic carriers) is slightly less complex. Metal carriers usually can be grasped under the SOM with a pair of Steiglitz forceps after solvent has been used to remove the majority of the gutta-percha that surrounds the carrier. Most often, upon access into the crown of such a tooth, the coronal ends of the obturators can be isolated and grasped as described. Such retreatment should not be contemplated without the use of a SOM and advanced training. It may also be helpful to use an ultrasonic tip, which can be placed directly onto the coronal end of the metal carrier tip, which should be freely exposed in the chamber to vibrate the obturators and free them up in addition to the other techniques mentioned here.
It is entirely possible in a clinical case that the distal root may also have 2 canals. Visualization through the SOM would allow the clinician to know for certain if 2 canals were present, and if a second distal canal is present—whether it branches off from the main canal at or below the level of the pulpal floor.
This will probably be a 2-visit retreatment procedure. The first visit will likely be needed to get the obturators out and allow for any drainage through the crown. Again, as in the second case, this is likely to be a 2-visit treatment utilizing calcium hydroxide between the visits. In addition, the same concerns regarding regaining apical patency apply to a case as did case No. 2.
Three clinical cases have been described to demonstrate treatment-planning principles that will have value to the clinician when evaluating previous root canal treatment. Emphasis has been placed on evaluating the existing coronal seal, the presence of uncleaned and unfilled spaces in the root canal system, techniques for gaining patency, and the removal of obturators.
Disclosure: Dr. Mounce is on the Advisory Board for SybronEndo and does receive an honorarium for some aspects of this work, for example, some lectures.
Dr. Glassman graduated from the University of Toronto, Faculty of Dentistry in 1984 and was awarded the James B. Willmott Scholarship, the Mosby Scholarship and the George Hare Endodontic Scholarship for proficiency in Endodontics. A graduate of the Endodontology Program at Temple University in 1987, he received the Louis I. Grossman Study Club Award for academic and clinical proficiency in Endodontics. The author of numerous publications, he is on staff at the University of Toronto, Faculty of Dentistry in the graduate department of endodontics. Dr. Glassman is a renowned international lecturer on endodontics. He is also a Fellow of the Academy of Dentistry International, the Pierre Fauchard Academy, and the Academy of Dental-Facial Aesthetics. He is the endodontic editor for Oral Health. He is Past President of the George Hare Endodontic Study Club and the H.M. Worth Radiology Study Club. Dr. Glassman maintains a private endodontic practice in Toronto, Ontario. He can be reached through his Web site at rootcanals.ca.
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