Comparison of the relative risk of molar root perforations using various endodontic instrumentation techniques

One hundred canals in the mesial roots of 60 mandibularmolars were instrumented using five techniques. The remaining 20 canals became uninstrumented controls. A standard technique without flaring and four techniques with flaring were evaluated. In two of the flare techniques only hand instrumentation (circumferential and anticurvature) was used while in two others additional engine-driven instrumentation (round burs and Gates-Glidden burs) was used. Of the flare techniques, hand instrumentation used in an anticurvature manner showed significantly less risk (p