Authors: Davis MS, Joseph SW, Bucher JF.
Title: Periapical and intracranial healing following incomplete root canal fillings in dogs.
Journal: Oral Surg Oral Med Oral Pathol
Date: May 1971
Citation: 31(5):662-75
Category: Success and Failure
Evidence-based Ranking: 5
Purpose/Objective: To study the reactions of the periapical tissues of dogs to hollow tubes in the form of widely prepared but underfilled root canals following vital pulp extirpation and to determine how healing would occur in this environment.

Materials and methods: 32 root canals in four dogs were treated endodontically. The mandibular 3rd and 4th premolars were used. The teeth were isolated with a rubber dam. All canals were prepared to within 1mm of the radiographic apex up to the size of a no. 80 file. The canals were filled with gutta percha by lateral condensation. Dogs 1, 2 and 3 had left side filled to the working distance and all canals treated on the right side were filled 3mm short of the radiographic apex. Dog 4 had 2 canals filled to the working length, 2 canals filled 3mm short and 4 canals grossly overfilled. Radiographs were taken preoperatively, immediately postoperative and follow up just prior to sacrificing the animal which was 17 weeks after RCT. The dogs were observed periodically for signs of inflammation or infection throughout the observation period.

As the teeth were taken and observed, it was broken down into 5 groups: I: grossly overfilled with gutta percha and sealer (4 canals), II: filled to apex with extruded sealer particles (5 canals), III: filled to working distance within 1mm of apex (9 canals), IV: instrumented to within 1mm of apex filled 3mm short (6 canals), V: instrumented to or slightly beyond apex, filled 3mm short (8 canals).

Results: Postoperative observation revealed no apparent signs of inflammation or infection until 15 weeks after the completion of RCT. Dog 4 developed a parulis on the internal aspect of the mandibular mucosa adjacent to the apex of one of the overfilled canals. 2 of the canals in Group II were associated with bone loss, but considerable new bone formation was evident. In one of these cases, bone destruction was seen with an area of intense chronic inflammation. The other 3 canals exhibited mild periapical inflammation confined to the areas adjacent to the extruded sealer particles with little evidence of bone destruction. Group III had 6 canals associated with normal intact periodontal tissues with little or no evidence of inflammation. 2 canals exhibited moderate amounts of chronic inflammatory infiltrate in the pdl with minimal bone destruction and with new bone and cementum formation. Overall success rate was high, 8 of 9. Group IV consisted of 6 canals had some chronic inflammatory infiltrate present in the periapical tissues. 3 had moderate to marked inflammation, bone loss and liquefaction necrosis while the other 3 had mild inflammation with no significant loss of bone. Group V had 8 canals that exhibited generally excellent healing with some cases having canal space filled with viable tissue in the form of a complete and apparently functional attachment apparatus which was continuous with the periodontium.

Reviewer’s comments: The study was a dog model and not in humans; small number of canals treated. Excessive enlargement of the apices was done (size 80). Also, specific treatments for each dog were not randomly distributed; only one dog had all the overfilled canals.