An in vitro evaluation of canal preparation using Profile .04 and .06 taper instruments.

A model system involving a double radiographic exposure technique was developed in order to evaluate maintenance of the original canal path of curved root canals. The mesiobuccal roots of 30 maxillary molars were prepared using one of three techniques (n = 10 in each group). One group was instrumented using rotary Profile .04 tapers and a second group was prepared using orifice openers, rotary Profile .04 and .06 tapers. The final group was prepared using Profile hand files .02 taper and Gates-Glidden drills. Canal transportation was evaluated in the apical, middle and coronal regions from the double-exposed radiographs. Canal shape was determined by the ease with which a D11T spreader passed to within 1 mm of the working length. Time of instrumentation was also recorded. The results showed no significant difference between the techniques in canal transportation in the apical, middle or coronal regions (P > 0.05). It was significantly easier to place the D11T spreader in the .06 taper group (P < 0.05). Canal preparation was significantly quicker in the .04 taper group (P < 0.05). In conclusion, the use of .06 taper files improved canal shape and did not increase transportation. The additional file changes, however, increased the instrumentation time.