Changes in root canal geometry after preparation assessed by high-resolution computed tomography

Root canal morphology chanties during canal preparation, and these changes may vary depending on the technique used. Such changes have been studied in vitro by measuring cross-sections of canals before and after preparation. This current study used nondestructive high-resolution scanning tomography to assess changes in the canals' paths after preparation. A microcomputed t omography scanner (cubic resolution 34 mum) was used to analyze 18 canals i n 6 extracted maxillary molars. Canals were scanned before and after prepar ation using either K-files, Lightspeed, or ProFile.04 rotary instruments. A special mounting device enabled precise repositioning and scanning of the specimens after preparation. Differences in surface area (DeltaA in mm(2)) and volume (DeltaV in mm(3)) of each canal before and after preparation wer e calculated using custom-made software. DeltaV ranged from 0.64 to 2.86, w ith a mean of 1.61 +/- 0.7, whereas DeltaA varied from 0.72 to 9.66, with a mean of 4.16 +/- 2.63. Mean DeltaV and DeltaA for the K-File, Profile, and Lightspeed groups were 1.28 +/- 0.57 and 2.58 +/- 1.83; 1.79 +/- 0.66 and 4.86 +/- 2.53; and 1.81 +/- 0.57 and 5.31 +/- 2.98, respectively. Canal ana tomy and the effects of preparation were further analyzed using the Structu re Model Index and the Transportation of Centers of Mass. Under the conditi ons of this study variations in canal geometry before preparation had more influence on the changes during preparation than the techniques themselves. Consequently studies comparing the effects of root canal instruments on ca nal anatomy should also consider details of the preoperative canal geometry .