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ePaper created 2017-11-24, 11:00:53 | version 1.38.0
| study defects after preparation Assessment of dentinal defects Statistical analyses Under water-cooling (Isomet; Buehler Ltd, Lake Bluff, IL, USA), the roots of 80 specimens were cut per- pendicular to the tooth axis at 3, 6, and 9 mm distant from the apex, and 3 slices were obtained from each specimen. Trans-illumination was applied to the slices from 1 mm distance in mesial, distal, buccal, and lin- gual directions using a LED (LED Light; Denshine Tech- nology, China) device. The digital images (4 images from each slice) were taken under x25 magnification using a digital camera connected to stereomicroscope (Olympus BX43, Olympus Co, Tokyo, Japan). In order to eliminate the bias of observers, the canals on digital images were masked using a circular drawing. A total of 960 digital images—240 from each group—were examined to determine if any cracks were present. The images obtained were then randomly assigned to two experienced endodontists, who were not involved in In examining the intergroup incidence of dentinal defects, a Chi-Square test was used. The level of sta- tistical significance was set to 5 %. The statistical analyses were performed using SPSS 21 (IBM-SPSS Inc., Chicago, IL, USA) software. Results In the present study, 960 images taken from 240 tooth slices were examined. The distribution of den- tinal defects caused by the tested NiTi file systems between apical, medial, and coronal regions is pre- sented in Table 1. In the present study, no statisti- cally significant difference was found among the NiTi files tested and between them and control group in terms of the total number of dentinal de- fects (P > 0.05). Fig. 1: Samples of slices obtained at different distance from the apex presenting dentinal defects. (a) Control Group, (b) HyFlex EDM, (c) WaveOne Gold, and (d) ProTaper Gold. Fig. 1a Fig. 1b Fig. 1c Fig. 1d “In the present study, no statistically significant difference was found among the NiTi files tested and between them and control group in terms of the total number of dentinal defects (P > 0.05).” the preparation of the specimens, in order to deter- mine the presence or absence of dentinal defects. To define crack formation, two different categories were made (i.e. ‘no crack’ and ‘crack) to avoid the confusing description of root cracks. ‘No crack’ was defined as the root dentine without cracks or craze lines either at the internal surface of the root canal wall or the external surface of the root. ‘Crack’ was defined as all lines ob- served on the slice that either extended from the root canal lumen to the dentine or from the outer root sur- face into the dentine (Shemesh et al. 2009) (Fig. 1). Discussion In this study, the dentinal defects created by HEDM, WOG and PTG NiTi file systems on mandibu- lar molar teeth’s mesial canals were evaluated. Ac- cording to the results of the present study, it was determined that all of the tested NiTi files created dentinal defects but no statistically significant dif- ference was found when compared to thecontrol group. For this reason, the null hypothesis of the present study was accepted. 26 roots 4 2017