A comparison of molar root canal preparations using six instruments and instrumentation techniques.

Six different instruments (Flexofile, Canal Master U, Heliapical, Flexogate, Ultraflex, and Lightspeed) were evaluated in 240 mesial canals of extracted mandibular molars (40 canals per instrument type). After instrumentation, the roots were cross-sectioned 2, 5, and 9 mm from the apex. The cross sections were evaluated to determine the quality of canal preparation (round, oval, irregular). The best results were obtained with nickel-titanium, a short cutting blade and a rotary rather than a filing motion. The Canal Master U, Flexogate, and Lightspeed instruments had significantly more round canals than the Flexofile, Heliapical and Ultraflex instruments at all levels. The Lightspeed had the largest number of round canals at all levels. Instrumentation time was also recorded. The Canal Master U and Flexogate were significantly slower than the Flexofile, heliapical, Ultraflex, and Lightspeed instruments. There were no statistically significant differences within the faster group.