Impact of Case Difficulty on Endodontic Mishaps in an Undergraduate Student Clinic.

INTRODUCTION: The aim of this study was to identify the effect of case difficulty on the number of endodontic mishaps and the number of treatment visits using 2 different instrumentation methods, hand files, and reciprocating engine-driven WaveOne files (Dentsply Maillefer, Ballaigues, Switzerland) in an undergraduate student clinic. METHODS: Endodontic treatment performed by fourth-year dental students using 2 different instrumentation methods was evaluated: hand files and reciprocating engine-driven WaveOne files. All cases were categorized according to the American Association of Endodontists case difficulty assessment form. Endodontic mishaps related to instrumentation and treatment visits needed to complete the treatment were recorded. RESULTS: Of the 257 teeth included in the study, 141 were instrumented with hand files and 116 with WaveOne files. Eighty-two teeth (31.9%) were registered with at least 1 endodontic mishap. The most frequent endodontic mishap was overinstrumentation (17.5%). This was followed by loss of working length (8.56%), obturation more than 2 mm from the radiographic apex (8.56%), overfill with gutta-percha (6.61%), canal transportation (4.28%), instrument separation (2.33%), and lateral or strip perforation (1.56%). Several endodontic mishaps were significantly correlated. Cases in the high difficulty category had significantly more endodontic mishaps (P < .001) and required more treatment visits (P < .01). There were no significant differences in endodontic mishaps or the number of treatment visits between the hand and engine-driven groups. Several endodontic mishaps were associated with significantly more treatment visits (P < .05). CONCLUSIONS: Case difficulty rather than the instrumentation method was the main determinant of endodontic mishaps in the undergraduate clinic. The American Association of Endodontists case difficulty assessment form is an important and valuable tool in undergraduate dental education to predict potential endodontic mishaps and the number of treatment visits.