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Abstract
Objectives
The purpose of this study was to determine the optimal master apical file size with minimal transportation and optimal efficiency in removing infected dentin. We evaluated the transportation of the canal center and the change in untouched areas after sequential preparation with a #25 to #40 file using 3 different instruments: stainless steel K-type (SS K-file) hand file, ProFile and LightSpeed using microcomputed tomography (MCT).
Materials and Methods
Thirty extracted human mandibular molars with separated orifices and apical foramens on mesial canals were used. Teeth were randomly divided into three groups: SS K-file, Profile, LightSpeed and the root canals were instrumented using corresponding instruments from #20 to #40. All teeth were scanned with MCT before and after instrumentation. Cross section images were used to evaluate canal transportation and untouched area at 1- , 2- , 3- , and 5- mm level from the apex. Data were statistically analyzed according to' repeated nested design'and Mann-Whitney test (p = 0.05).
Results
In SS K-file group, canal transportation was significantly increased over #30 instrument. In the ProFile group, canal transportation was significantly increased after preparation with the #40 instrument at the 1- and 2- mm levels. LightSpeed group showed better centering ability than ProFile group after preparation with the #40 instrument at the 1 and 2 mm levels.
Figures and Tables
Figure 1
Measuring the distance and the angle between original center and deviated center. a: original center of the canal. b: deviated center after preparation. Canal transportation (by distance) : Distance between a and b. Canal transportation (by degree) : A positive value indicates a movement of the canal center in the outer root surface (purple arrow), while a negative value signifies a shift in the opposite direction (green arrow).
* Original canal wall was drawn by red line and canal wall after preparation by black line.
Figure 2
Cross sectional images acquired by µCT illustrate the sequential canal deviation by each group of instrument. Profile and Lightspeed group show more round and less deviated canal shapes.
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