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ePaper created 2017-11-24, 11:00:53 | version 1.38.0
| study defects after preparation to cause less dentinal defects. Similar to the results of other studies (Capar et al. 2014, Li et al. 2015), the researchers attributed these results to the heat treat- ment, to which WaveOne files are exposed. Karata et al. (2015a) have examined the dentinal cracks cre- ated by ProTaper Universal, ProFile Vortex (Dentsply Maillefer), ProTaper GOLD, Reciproc (VDW, Munich, Germany), and F360 (Komet Brasseler, Lemgo, Ger- many) files systems in mandibular incisor teeth, and reported that there was no statistically significant dif- ference between ProTaper Universal, ProFile Vortex, ProTaper GOLD and Reciproc groups in terms of den- tinal defect formation. It is believed that the reason for the difference in the present study originates from the differences in methodologies used. Similar to the pres- ent study, Coelho et al. (2016b) have used LED in inves- tigating the dentinal defects created by ProFile (Dent- sply Maillefer), TRUShape (Dentsply Maillefer) and WaveOne GOLD systems on mandibular molar teeth’s mesial canals, and reported statistically non-signifi- cant differences between the negative control group and experimental groups in terms of dentinal defects. Capar et al. (2014) have examined the dentinal de- fects created by HyFlex CM, ProTaper Universal and ProTaper Next NiTi file systems on mandibular premo- lar teeth during preparation procedure. The research- ers have reported ProTaper Next and HyFlex CM files to cause less dentinal defects than the ProTaper Uni- versal files. Ashraf et al. (2016) have examined the dentinal defects created by ProTaper Universal, Pro- Taper Next and HyFlex CM NiTi file systems in mandib- ular premolar teeth by using sectioning method. Re- searchers have reported that HyFlex CM files caused less cracks than ProTaper Universal and ProTaper Next files did. In our literature review, it was determined that HEDM files’ dentinal defect incidence had not been studied before. For this reason, it is not possible to directly compare the results of the present study to those of others. In a finite elements analysis, it has been shown that increasing the taper of files also in- creased the stress on root canals during shaping pro- cedure (Kim et al. 2010). Bier et al. (2009) reported that the taper of files might influence dentinal defects on roots during the shaping procedure. Yolda et al. (2012) have alleged that the tip design, cross-section, constant or variable taper, and groove and pitch struc- ture of NiTi files might be related with the formation of dentinal defects. However, it is not exactly known how the taper of files affected the results of present study, because the taper of files used were not same and the taper of HEDM file was not known. The similar results obtained are thought to originate from the fact that the files were made of alloys having no shape memory (Gold and CM). shaping was three times more than that on the apical third. Despite that, Kim et al. (2010) have reported the stress on the apical third during shaping of the curved root canals to be more than that on the middle and cor- onal third. According to the results of the present study, there was statistically non-significant differences be- tween the dentinal defects created by NiTi file systems on the apical, middle, and coronal third, and this finding is believed to originate from the fact that the files were made of alloys having no shape memory (Gold and CM). Even though it was important to simulate the clinic conditions in a laboratory environment in the present study, especially in the studies on examining the me- chanical properties of teeth, many external factors such as storing the teeth after extraction and until the sectioning procedure affected the results of study (Bürklein et al. 2013). For this reason, as stated by Coelho et al. (2016b) in their study, the use of teeth ex- tracted using periodontal reasons, which require very low level of force during extraction, and the careful storage of these teeth until the sectioning procedures would allow for more successful outcomes. Another limitation of present study is the difficulty of stand- ardisation of apical pressure applied by the operator during root canal shaping procedure and that this may influence the results. Conclusion Within the limitations of the present study, no statistically significant difference was found among the HEDM, WOG, PTG and the control group in terms of the total number of dentinal defects._ Editorial note: List of references is available from the pub- lisher. contact Dr Taha Özyürek, DDS, PhD; Ondokuz Mayis University, Faculty of Dentistry, Department of Endodontics Samsun, Turkey tahaozyurek@hotmail.com Dr Mustafa Gündo ar, DDS, PhD; Department of Endodontics, Faculty of Dentistry, stanbul Medipol University, stanbul, Turkey Dr Gül ah Uslu, DDS, MSc; Private Practice, Dental Clinic, Çanakkale, Turkey Versluis et al. (2006) have reported that the level of stress on coronal and medial third during root canal Dr Koray Yılmaz, DDS, MSc; Çorum Oral and Dental Health Center, Çorum, Turkey 30 roots 4 2017