A Comparison of Mesial Molar Root Canal Preparations Using Two Engine-Driven Instruments and the Balanced-Force Technique

Abstract

The purpose of this study was to compare the effects of two engine-driven, nickel-titanium instrument systems with hand files in the final shape of slight and moderately curved canals. A total of 72 mesial roots of extracted human mandibular molars were divided into three groups: ProFile .04 taper, Pow-R rotary systems, and Flex-R hand-filing technique. The roots were mounted and cross-sectioned at two different horizontal levels using a modified Bramante technique. Pre- and postinstrumented cross-sectional roots were imaged, recorded, and computer analyzed. Results showed that, at the middle third, in almost all groups, there was a tendency of cutting more toward the mesial side with only one exception: Pow-R cut more to the distal side (danger zone) (p < 0.02). At the apical third, Flex-R (p < 0.03) and ProFile (0.001) transported to the mesial side (danger zone) when the curvature increased. When the three techniques were compared analyzing each side and considering the two groups of curvature, at the middle third in the moderately curved-canal group, Flex-R cut statistically more than Pow-R toward the lingual side. The other comparisons showed no statistically significant difference. When the techniques were compared in relation with the degree of curvature, in the apical third, ProFile .04 cut statistically more toward the mesial side in the moderately curved canal group than in the slightly curved canal group. The other comparisons showed no statistically significant difference. Canal preparation time was shorter with hand instrumentation (p < .05) in a few instances.

A Comparison of Three Ni-Ti Rotary Instruments in Apical Transportation

“…After reassembling the sections, the canals are instrumented and once again re-evaluated for postinstrumentation changes. The labor-intensive reassembly technique yields excellent results but many teeth are lost because of ledging caused by gaps between sections of the roots (10,11). The use of high-resolution computed tomography to study root canal anatomy is a promising tool; however, it is time consuming and expensive (5,12).…”

Assessing apical transportation in curved canals: comparison between cross-sections and micro-computed tomography

“…[5][6][7][8][9][10] The limitations of each of these methods have been extensively discussed, 11,[20][21][22][23] encouraging continuing research into technologies that allow both quantitative and qualitative three-dimensional assessments of the root canal. To this end, the present study compared the µCT and the cross-sectioning methods used to quantify apical transportation after rotary instrumentation of curved canals at 2.0, 3.5, and 5.0 mm from the apex.…”

“…The main advantages of this widely-used method are the possibility to compare the root canal structure before and after instrumentation, and the fact that the analyzes are conducted in the real image of the root canal. 10,11,20,21,24 However, disadvantages have also been described, e.g., assessment restricted to limited portions of the root canal, insofar as this is a two-dimensional technique, and material may be lost from serial tooth sectioning. Moreover, it is an invasive method, with irreversible changes to specimens.…”

“…Other authors have also described this loss of root structure as leading to slight discrepancies between sections. 11,20,21 Nonetheless, although the cross-section method obtains faithful measurements based on the real image of the specimen, sectioning of the roots does not allow simulation of clinical conditions during root canal preparation.…”

“…11 Moreover, the two-dimensional projections of three-dimensional structures provided by this method do not adequately represent the real object, reducing the accuracy of the analyses performed in quantitative studies. 12 The search for more reliable and less invasive methods to assess apical transportation has led to the widespread use of micro-computed tomography (µCT) in endodontic research.…”