Hidden Missed Canal

Terry Pannkuk, DDS, MScD Diagnosis, Access, Cleaning and Shaping, Complications: Advanced Management, Missed Canals, Retreatment Strategies


Patient: 70 year old female in good health

Chief Complaint: Localized pain associated with the maxillary right second bicuspid

Dental History: The root canal treatment had been performed by her dentist in two visits separated by 2 weeks. She was in pain before the first visit and in no pain on the second final visit which was two months ago. Her symptoms just started a few days ago.

Significant Findings of Interest: Severe percussion sensitivity localized to the maxillary right second bicuspid (#4), 6mm wide periopocket at the mesial aspect and all probing points bled, Normal occlusion. No palpation sensitivity at the cervical or apical areas.

Differential Diagnosis:

  1. Strip perforation of the inside of a root curve with resultant acute apical periodontitis
  2. Missed canal with resultant acute apical periodontitis
  3. Acute periodontitis
  4. Root fracture with resultant acute apical periodontitis

After CBCT Scan-Diagnosis: Missed Canal (failing previous endodontic treatment) with acute apical periodontitis

Prognosis: Fair due to previously weakened root

Note: Once the CBCT slicing progressed past the cervical area, No hemispherical radiolucencies were seen suggestive of a root fracture. The mesial pocket seemed to be a standard coincidental angular perio defect (primary periodontitis unrelated to endodontic pathosis).

Treatment Plan: Nonsurgical Endodotnic Retreatment (two steps with calcium hydroxide)

Treatment Description with Special Considerations: CBCT imaging demonstrated a deep split and missed second canal. On the first visit the previous root canal filling material was removed, the access was extended to achieve a direct line to the missed branch; the entire root canal system was cleaned and shaped, and then filled with calcium hydroxide. Initial perio therapy was instituted to address the coincidental primary periodontitis and an appointment was scheduled to finish treatment one month later after resolution of symptoms and disease. If the periodontal status did not improve, it was suggested to remove the crown. The patient had a considerable investment in this tooth so it was important to assess outcome at each decision point before progressing further toward definitive treatment and restoration. No crack or perforation was found.

If surgery had been performed a lowered prognosis would be accepted without defining the etiology and having no understanding of the internal root canal system anatomy associated with the extension of disease. Apical resection and reverse filling may leave a significant track of septic percolation, which is just a matter of time before it compromises the case again. Definitive ideal treatment should be proposed first, leaving the surgical option as a secondary backup option. Nonsurgical retreatment was performed with predictable achievement of all objectives by creating adequate occlusal access extended toward the buccal and creation of a direct line without overshaping the already over-filed inside curves of the roots. This case demonstrates the concept of passive instrumentation described by Schilder. With patience and care the previous gutta percha can be removed without aggressively shaping the prep wider and risking a strip perf on the inside of the S-curve.

Oval anatomy is not addressed well by rotary instruments so the cleaning and shaping was performed primarily with precurved K-files.

The the key feature of the Schilder cleaning and shaping technique is to randomly contact dentin walls via the envelope of motion achieving eventual thoroughness after multiple recapitulations and flushing with irrigants.

Hedstroms require special finesse and can be dangerous. They can smooth out an irregularity almost instantly, but if one cuts into a curve with the tip there will be a ledge. The can be used sparingly for special circumstances and only after complete control of the apical prep being cleared and patent. K-files are extremely safe but not particularly efficient; whereas Hedstroms are extremely efficient and not particularly safe. Other files are at various points along the continuum inbetween safety and efficiency. It's largely personal preference. This author prefers safety as opposed to efficiency to achieve idealized objectives.

The patient’s symptoms were eliminated after completion of treatment.

Key Learning Objectives:

  1. Nonsurgical retreatment provides a more definitive and predictable result compared to surgical retreatment
  2. Bicuspids frequently have more than one canal often with deep bifurcations and complex ramifications.
  3. Extended direct line access is particularly important in treating teeth likely to have complex root anatomy
  4. CBCT imaging can help find subtle canals that would otherwise be missed.

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