My Casebook

A Zipping Perforation Revisited

The patient seeked a second opinion after being advised to have her second lower molar removed and replaced with another implant supported crown. The first molar had previously been replaced by just such a prosthesis. (Figure 1)

The patient's history was non-contributory. Her main complaint was that of tenderness and occasional pain of the tooth in question. Careful examination of the tissues showed some percussion tenderness of the tooth, but significantly, no periodontal pocketing or visible cracks. The radiographic view (Figure 1) was clearly that of overzealous shaping of the mesial canals, termed zipping, with weakening of the canal walls and even possible perforation, predisposing to the diagnosis of peri-radicular periodontitis.

After explaining to the patient the significance of the findings, especially the compromised status of the root structure, she nevertheless elected to have a re-treatment of the root canal of the second lower molar. Contributing to her decision was her previous experience of implant therapy, that of the first molar, adjacent to the tooth presently under consideration.

Re-treatment was carried out. The final post-operative radiograph clearly showed some extrusion of filling material into the peri-radicular tissues, exactly in the area of the zipping lesion. (Figure 2) 

At the time of writing, the patient's symptoms had disappeared but the case will be closely monitored.

What can we learn from this case?

Firstly, patients do not always share practitioners's enthusiasm for implant therapy. This is good because there is a worldwide tendency, even more pronounced in South Africa, amongst dental practitioners, to sacrifice natural teeth in favour of implant supported teeth. I frown heavily upon this prejudice.

Secondly, enthusiasm is a good thing, but it can also be dangerous. It is good to properly shape and clean root canals, but... It is equally bad when one destroys too much tissue. The secret is to know when enough is enough. In one sentence: A canal has been adequately shaped when access to the apical third, for 1. an irrigation needle 2. a GP cone and 3. a condensing instrument has been created. In this case the mesial canals had been over shaped, to such an extent that the so-called "zipping" had pre-disposed to a perforation. I freely admit that the actual perforation may have been caused by myself during the re-treatment, but Figure 1 clearly shows how thin the walls of the mesial canals had been left by the original practitioner. Perforation, inevitable, as it had been, however is no absolute contra-indication to endodontic re-treatment. In the final analysis, the decision always rests with the patient. 

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