Ten-year Clinical Experience and Laboratory Validation of the Modified Tube Technique for Removing Fractured Endodontic Instruments using In Vivo Collected Samples.

INTRODUCTION

Numerous techniques have been proposed for the reliable removal of separated instruments from root canals. In 2015, the modified tube technique (MTT) was introduced, whereby an optical fiber is inserted down to the lumen of a cannula containing composite resin in its tip. The cannula/composite devise is then inserted around the exposed fragment end, entrapping the instrument prior to the light curing of the resin via the optical fiber. This study evaluates the transfer of laboratory findings into clinical practice and vice versa.

METHODS

A total of 278 separated instruments were removed during endodontic retreatment therapy, primarily using ultrasonic devices and the loop technique. In this collection, 20 fragments (7.19%) were ultimately retrieved using the MTT after conventional techniques had failed. The in vivo obtained cannula-fragment complexes were analyzed radiographically and subjected to tensile strength testing. The ratio of force to estimated lateral surface area lateral surface area (N/mm2) was calculated and statistically analyzed using Spearman's correlation.

RESULTS

The median fragment length was 4.085 mm with a diameter of 0.2 mm. An overlap of approximately 1.06 mm within the cannula enabled a tensile strength of 44.668 N. A strong positive correlation was observed between lateral surface area and applied force (ρ = 0.844). The mean estimated force-to-area ratio was higher for steel instruments (91.38 N/mm2) than for Nickel-Titanium instruments (55.54 N/mm2).

CONCLUSIONS

The MTT appears to be a reliable approach for the retrieval of separated instruments, generating high retention forces with a mean fragment exposure of only 1.06 mm. As a minimally invasive, adhesive-assisted microtube technique, MTT represents a promising treatment option for cases in which conventional retrieval methods are unsuccessful.