Basic Research-Technology
Complications Associated with Fractured File Removal Using an Ultrasonic Technique

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Abstract

A technique utilizing modified Gates Glidden burs and ultrasonics has recently been advocated to remove fractured instruments from root canals. Varying extents of tooth structure are removed during this procedure, potentially leading to complications. This study evaluated the in vitro and in vivo complications associated with fractured file removal. Fractured instrument fragments were removed from three different levels (coronal, middle, or apical third) of mesiolingual canals of extracted human mandibular molars. The success rate, frequency of perforations, and root strength were recorded for each group. Perforations and unsuccessful file removal occurred only with fragments lodged in the apical third. Fracture resistance declined significantly with more apically located file fragments. A review of 60 clinical cases showed similar rates of successful file removal and rate of perforations. Removal of a fractured file fragment from the apical third of curved canals should not be routinely attempted.

Section snippets

Experimental Study

Sixty extracted human mandibular molars with fully formed apices and no history of previous root canal treatment were used. All teeth were initially stored in 0.1% thymol following extraction and were continuously hydrated throughout the experimental procedure. The mesial roots were examined for pre-existing cracks at 25× magnification. All teeth were radiographed preoperatively and then accessed and any remaining pulp tissue was removed. Patency was established in the mesiolingual canals with

Experimental Study

Of the 45 teeth in the experimental group containing fractured instruments, 14 were classed as being in the coronal third, 16 in the middle third, and 15 in the apical third. Removal was successful in all cases where the file fragment was located in the coronal or middle third. Only 11 of the 15 files located in the apical third were successfully removed (Table 1). Stripping perforations occurred in three cases, all where the fragment was located beyond the curve (Table 1).

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Discussion

Many factors are involved when deciding how to deal with fractured instruments lodged within the root canal. If removal is attempted, the chances of success should be balanced against potential complications. Previous methods were often grossly destructive and unsuccessful (5, 16), but recently a more routinely safe and successful technique has been demonstrated (10, 11). This study confirms that this technique is highly successful in removing files lodged in the coronal and middle thirds of

Acknowledgments

This study was supported by grants from the School of Dental Science, The University of Melbourne, Australia, and The Australian Society of Endodontology, Inc.

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The authors thank Associate Professor Ian Gordon from the Statistical Consulting Center, The University of Melbourne, for assisting with the statistical analysis.

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