Case Histories
The etiology for endodontic failure has been attributed to both local and systemic factors, which have included the age and sex of the patient, the health of the patient, pre- and post-operative infection, and idiopathic phenomenon.
Although this list of etiologic agents for failure has been widely circulated, the author generally discounts the possibility that any one of these agents is a true cause of endodontic failure. It is believed, however, that the etiologic agents for failure are more simplistic: (1) inadequate removal of bacteria and bacterial substrate and (2) inadequate obturation or elimination of the root canal system.
The best evidence of this hypothesis is the post-operative result of a simple tooth extraction. When an abscessed tooth is removed from the oral cavity, few would argue that the rate of success is almost invariably 100%. The success rate is unaltered by things such as the age, sex or health of the patient, nor does it appear to be related to the prior existence of infection or the severity of that infection. Furthermore, post-operative failure only appears to occur when one fails to remove the tooth completely. The obvious conclusion that one draws from this analogy is that endodontics must fail only when the contents of the root canal system have been ineffectively eliminated, and when that system has been inadequately occluded/obturated.
Although the clinical realities dictate that endodontic success is predicated on (1) complete debridement and (2) total obliteration or three-dimensional obturation of the root system, it is understood that accomplishing this end is often complicated by complex anatomical configurations and/or iatrogenic mishaps. The following are case reports that address some of these complexities.
Case Report 1
Endodontic failure and retreatment including the removal of therma-fil carriers-multiple secondary (lateral) canals are noted.
A young adult male businessman presented with pain and palpation sensitivity associated with a previously endodontically treated upper first molar.
The clinical examination revealed a tooth that was sensitive to percussion and in slight hyper-occlusion.
The radiograph demonstrated an endodontic filling that approximated the anatomical foramina, however, the preparations appeared to be under-prepared. A small lateral root lesion could be visualized on the mesial aspect of the apex of the palatal root.
Endodontic retreatment was recommended. A minor occlusal adjustment was provided and the patient was given an 8-day course of Clindamycin 150 mgs t.i.d and Naprosyn 375 mgs as needed for pain. The patient was instructed to return in one week for treatment.
In the subsequent visit, a local anesthetic was administered and the tooth was isolated with a rubber dam. Using an operating microscope, an attempt was made to empty the canals using traditional right-hand helix rotary instruments. Although the gutta percha was removed relatively easily, portions of Thermo-Fil (plastic) carriers remained lodged in the apical extent of each canal. Additional work using Hedstrom files in a “bind and tug” modality was required to remove the carriers.
The canals were reprepared and disinfected with copious amounts of sodium hypochlorite. Obturation of the canals was completed using Schilder technique (warm gutta percha with vertical condensation) and Kerr sealer.
The final radiograph revealed multiple secondary (lateral) canals exiting the mesial aspect of the apex of the palatal root.
It becomes clear from comparing the pre-operative and the post-operative radiographs that the previous methodology was inadequate in sealing/obturating canals of extremely fine caliber such as those depicted in the computer enhanced film above. Thus, endodontic success is not only dependent on the skill and experience of the clinician, but on the selection of the technique and the materials chosen to perform the procedure.
Case Report 2
Endodontic failure and retreatment including the removal of a silver cone-a subradiographic secondary (lateral) canal is noted.
A healthy middle-aged female lawyer presented with intermittent pain and swelling associated with an upper left central incisor. The tooth had been previously endodontically treated by her general dentist many years prior. The patient had been referred to an endodontist on two separate occasions to eliminate the problem. Surgical endodontics had been attempted both times without success.
The clinical examination revealed chronic sinus (drainage) tract located above the apex of the offending tooth. A gray to black pigmentation 2-3mm in diameter was coincident with the drainage tract.
The radiograph demonstrated a loose-fitting silver cone in the endodontic cavity space (root canal) and a large retrograde amalgam that had been placed in the end of the root.
Endodontic retreatment was recommended. The patient was given 2000 mgs of Amoxicillin for the prophylactic treatment of a pre-existing heart murmur and instructed to return for a subsequent visit.
Following the administration of a local anesthetic and isolation of the tooth with rubber dam, a lingual access was gained with the use of an operating microscope. The previously placed silver cone was easily removed using reverse-thread CPT file. The canal was putrescent, and was cleansed and shaped uneventfully using a variety of modern hand instruments and copious amounts of sodium hypochlorite. The canal was obturated with using Schilder technique (warm gutta percha with vertical condensation) and Kerr sealer.
The patient returned for a two-week recall visit reporting the absence of pain and/or swelling. The clinical examination revealed that the drainage tract was closed. A subsequent visit was undertaken to complete an internal bleaching procedure and to replace the previous restorations.
Close examination of the final radiograph, using computer enhanced imaging, demonstrates a large lateral canal that had been sealed during the retreatment procedure. The lateral canal is so small that it cannot be traced radiographically. The dimension of this system, therefore, is less than 50 microns, which is the maximum resolution of “hard film” (the resolution of digital radiography is generally less).
Case Report 3
Endodontic failure and retreatment including the treatment of a fifth canal
A healthy young female student presented with persistent pain associated with a previously endodontically treated lower molar. The tooth had been treated approximately one year prior by a family dentist.
The clinical examination revealed a tooth that was sensitive to percussion and palpation. The tooth was also in hyper-occlusion.
The pre-operative radiograph demonstrated several poorly filled root canals with termini substantially short of the radiographic apex.
A minor occlusal adjustment was provided and a prescription for Augmentin 500 mgs was recommended t.i.d. Naprosyn 375mg be also prescribed to mitigate inflammation and further discomfort.
In a subsequent visit, a local anesthetic was administered and the tooth was isolated with a rubber dam. Using an operating microscope, the mesial canals were emptied using wide flute right-hand helix rotary instruments. The canals were renegotiated to the anatomical terminus with hand instruments.
A similar procedure was undertaken to negotiate the distal canals. The tooth presented as a typical lower molar with four canals. The canals were reprepared and disinfected with copious amounts of sodium hypochlorite. . The canal was obturated with using Schilder technique (warm gutta percha with vertical condensation) and Kerr sealer.
In addition to the four canals that had been cleansed and shaped, the post-operative radiograph demonstrated another canal intermediate to the mesiolingual and mesiobuccal canals, which had been obturated subsequent to the compaction. The fifth canal can be seen between the two mesial canals and demarcated at its terminus by a small amount of surplus sealer.
The patient returned for a six-month recall examination. The access cavity had been restored with an amalgam post-core restoration. The patient was asymptomatic and there was no further evidence of pathology.
Case Report 4
Endontic failure and retreatment including the removal of a “hard paste” root canal filling
A healthy middle aged long-shoreman presented with intermittent pain associated with a previously endodontically treated lower molar. The tooth had been previously treated his place of birth in Russia several decades prior.
The clinical examination revealed a tooth that was sensitive to percussion and palpation and a previously placed amalgam restoration that was in disrepair.
The pre-operative radiograph demonstrated a poorly filled distal canal. The mesial canals were unfilled. An antibiotic specific for anaerobes was prescribed in addition to an anti-inflammatory analgesic and the patient was rescheduled for treatment.
In a subsequent visit, a local anesthetic was administered and the tooth was isolated with a rubber dam. Using an operation microscope, the distal canal was emptied using Gates Glidden and broad flute right handed helix rotary instruments. The previous filling material was reminiscent of zinc phosphate cement (a commonly used material as a root canal filling material in the old USSR).
The canal was renegotiated to the anatomical terminus with hand instruments.
The mesial canals were also cleansed and shaped. The canals were disinfected with copious amounts of sodium hypochlorite and obturated with using Schilder technique (warm gutta percha with vertical condensation) and Kerr sealer. The access cavity was restored with an amalgam post-core restoration.
The patient returned for a one-month post-operative examination reporting relief of his symptoms and comfort when chewing.
Discussion
Although anatomical complexities such as secondary (lateral) and tertiary portals of exit are associated with a significant number of endodontic failures, the greatest number of failures is attributable to inadequate cleansing, shaping and obturation of primary canal spaces.
As we discussed earlier, endodontic success must be predicated on (1) complete debridement and (2) total obliteration of the root canal system. Unfortunately, these concepts are openly ignored by some and accepted only begrudgingly by others.
Considerable debate continues between well-educated clinicians regarding the terminal extent of the filling itself. Some still advocate filling the primary canal space l-2 mm short of the radiographic terminus. Although canals occasionally end slightly short of this terminus, there is no justification for ending the cleansing and obturating effort significantly short of the apex in every case. Furthermore, when we refer to the etiology for failure, it becomes increasingly evident that canals should be cleansed and filled to the extent of overfilling as opposed to underfilling. We are well aware of the biologic compatibility of gutta percha (a biologically inert elastomer) and Kerr sealer (essentially zinc-oxide and eugenol). We are also aware of the biologic incompatibility of the bacteria and bacterial substrate associated with an endodontically involved tooth. Thus, the author advocates filling all root canal systems to their radiographic terminus. The expression of small amounts of surplus sealer into the attachment apparatus is the normal sequelae of an endodontic delivery system that utilizes a hydraulic vector during treatment, which is biologically inconsequential.
Thus, the elimination of the patient’s symptoms and the rapid onset of healing in these cases are consistent with the premise that the endodontic cavity space must be completely cleansed and sealed to eliminate bacteria and bacterial substrate.
Although tooth extraction can accomplish the same objective, endodontic therapy that is thorough and complete is obviously a viable alternative.