Basic ResearchPreparation of Oval-shaped Root Canals in Mandibular Molars Using Nickel-Titanium Rotary Instruments: A Micro-computed Tomography Study
Section snippets
Materials and Methods
From teeth that had been extracted for reasons unrelated to the current study, a total of 200 human mandibular molars were collected. Distal roots were inspected under a stereomicroscope to verify that they had only one main portal of exit. The remaining 100 molars were prescanned using MCT (μCT 20; Scanco Medical, Brüttisellen, Switzerland) at a resolution of 68 μm. Based on a slice-by-slice assessment taking the distal root apex as a reference point, the slice 6-mm coronal of the apex was
Results
Preoperatively, there were no differences regarding overall and apical canal volumes among experimental groups (p = 0.56), indicating adequate randomization. Root canal preparation of distal root canals resulted in increased volumes (p < 0.001) with no significant differences among groups. Neither a ProTaper rotary instrument nor a Hedström file fractured in any of the experimental groups.
Figure 1 shows representative examples of superimposed root canal models before and after canal
Discussion
The main aim of this study was to compare commonly recommended methods to prepare root canals with long-oval cross section based on MCT reconstructions. Distal root canals in mandibular molars represented an adequate model for the present experiment, with a mean diameter ratio of 1:3.91 even at the 6-mm level. The present data suggest that the preparation of nonround canals leaves some canal surface uninstrumented. This finding was not related to the preparation strategy, and its extent was
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