Abstract
The purpose of this study was to compare the influence of dentinal defects (crazelines and incomplete fracture) after canal preparation withNi-Ti rotary (Twited file (TF) + Revo-S) and Hand (K – file) instruments, along with two different type of irrigation ( NaOCl + EDTA) and (CHX + EDTA). Seventy human single rooted teeth were used. The coronal portionof all teeth was removed by using a low speed disc with water coolingleaving roots measured 16 mm in length. Ten roots were left unprepared ( n = 10). The other roots were prepared either with manual Ni-Ti Khandfile (n = 20) or with two different rotary systems: 1. Twisted file (n = 20) and 2. Revo-S (n =20). All roots were sectioned perpendicular to the long axis at 3, 6, and 9 mm from the apex. Digital images of each section were captured at 40× magnification using a digital camera attached to a stereomicroscope (SZ 40-45, Japan). Eachspecimen was checked by 2 operators for the presence of dentinal defects. (crazelines and incomplete fractures) was noted. A total of 60 sections were examined in each group, except for unprepared group 30 sections were examined. Results of present study regarding to both types of irrigations (NaOCl + EDTA ), and ( CHX + EDTA) in the three tested instruments shows, no statistical significant difference. Yet, Revo-S system with (NaOCl + EDTA ) shows the highest number of defects, followed by Twisted , leand the lowest number of defects showed in K- hand fi