Friday, March 29, 2013
The natural tooth is the best implant. Rarely is the indication for both retreatment and implant therapy equally weighted between the two modalities. Each has a place.
In order to provide optimal service to the patient, the value of knowing when its time for retreatment, time for referral or time for extraction cannot be overstated. While implants have their place in the restoration of dental function and esthetics, endodontic therapy is generally less invasive and less expensive than the alternatives.
This column was written to discuss treatment-planning considerations in endodontic retreatment, and to specifically emphasize the importance of gaining patency as a clinical step in the process.
Given that clinical success rates for endodontic retreatments are essentially identical to implant success rates, arbitrary extraction of teeth that could successfully be retreated without giving patients all their options is a great disservice. Because they are the gatekeepers to either endodontists for retreatment or alternatively to surgeons for extractions and implants, general dentists have a pivotal role to play in determining which cases can and should be retreated.
Figure 1: Pre-operative view of #20. The previous root canal was completed several years prior and did not treat entire canal space.
Figure 2: Retreatment of #20 was completed in two visits. Calcium hydroxide was placed after the first visit.
While success of first time endodontic therapy is very high, failures occur, some with a clear mechanism of failure and others without. How these failures occur is due to an extensive set of complex factors that most often is within the control of the clinician. Assessing cases correctly prior to treatment goes far toward achieving the desired result after treatment.
As a full-time practicing endodontist, it is my observation that failure is most often preventable and has much more to do with assessment of the risks before treatment than any other single factor.
For example, recognizing a furcal floor fracture based on all the information present via 2D and 3D radiographic assessments of the tooth and evaluation of the bone support, percussion, palpation, mobility and probing, among other means can be a key way to avoid such a failure. Obviously removing these fractures from the retreatment side of the ledger avoids unproductive procedures. Alternatively, judging that a tooth has a vertical fracture when it in fact does not, achieves just the opposite.
Figure 3: Pre-operative view of #4 and #5. Both teeth when accessed showed evidence of coronal leakage and uncleaned and unfilled space within the root canal system.
In essence, taking financial considerations out of the equation and comprehensively assessing the clinical factors such as previous treatment quality, the periodontal condition and the contemplated final restoration for the tooth—including what loads it will be asked to carry—is essential before embarking on treatment in order to give the patient the best opportunity to retain their tooth where indicated.
Once a decision to begin treatment has been made, several goals are paramount in the mind of the specialist retreating a failed root canal treatment. These include, removing the existing restorations, posts, and endodontic filling without acerbating or causing any iatrogenic issues, repairing iatrogenic issues if present, gaining patency, cleaning, shaping and obturating the canal and placing a coronal seal prior to the coronal restoration. In essence, retreatment is a strategy to revise the previous treatment, and in the process remove to the greatest degree possible the bacterial source of failure, to facilitate healing.
Figure 4: Post operative view after retreatment.
Of these goals above, the least appreciated aspect of retreatment is the time spent attempting to recapture the canal path during retreatment. The feasibility of gaining patency in the hands of a specialist to negotiate previously untreated canal space is paramount to the success of retreatment procedures. This is intimately related to decision making relative to whether the tooth is a candidate for apical surgery or possibly extraction.
Radiographic interpretation of cases, even with cone beam technology, can be challenging. With this caveat, if the canal appears hopelessly ledged and a lesion is present, retreatment is obviously less predictable. Alternatively, if the filling is centered in the root and negotiable canal appears below the obturation, when the gutta percha is removed, it most often is. Caution and clinical judgment are advised.
Using the correct type, sequence and manual pressure with hand files is essential to avoid blocking the root during negotiation, getting around a ledge or preparing a glide path once the canal is negotiated. While a technical and detailed description of this series of steps is beyond the scope of this article, the use of stiff and small hand files is essential early in the process of canal negotiation. While preferences for individual hand file brands vary, almost always starting with small and stiff hand files sizes, #6, #8, #10 (in this order) give the best chance to negotiate a canal during either first time treatment or retreatment.
Mani D Finders are the equivalent of a stiff carbon steel instrument used for canal negotiation in such cases. Precurving the D finder, introducing it with gentle pressure in every possible orientation in the canal to gain patency, not advancing file sizes until the first and smaller file will spin freely are all strategies for canal negotiation and are especially important in cases of endodontic retreatment.
In addition, having the correct length of file is vital. A hand file that is too short to reach the minor constriction of the apical foramen risks blockage of the apex with debris as well as transportation.
A concise description of conceptual goals in endodontic treatment has been presented. Emphasis has been placed on a thorough case assessment, realistic decision making of the weight of clinical predictability between endodontic retreatment and implants and the value and importance of gaining patency during retreatment. I welcome your feedback.