الفهرس 
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Abstract
The current study was conducted to evaluate and compare the dentinal crack formation of Kedo-SG Blue file and Wave-One Gold in comparison with Stainless Steel hand K files after root canal preparation in primary molars using Scanning Electron Microscope (SEM).
Seventy five primary mandibular second molars with at least two thirds of intact mesial roots were collected, disinfected and then stored in sterile saline solution at room temperature until experiments were conducted.
The selected teeth were randomly allocated to three experimental groups of 25 teeth each, according to the type of instrumentation used to clean and shape the canals. The root canals were prepared in a standardized instrumentation procedures with Kedo-SG Blue, Wave One Gold and K- files for group I, II and III respectively.
After instrumentation, roots were sectioned at three different level(coronal, middle and apical thirds) using a water-cooled, low-speed saw then inspected under SEM to evaluate the incidence of dentinal defects after root canal instrumentation.
The results from this study showed that manual and rotary groups develop crack after root canal preparation. But there was a statistical significant difference between different file types in coronal, middle and apical where (p=0.043), (p=0.003), (p=0.013) respectively.
Over all percentage of cracks in all sections were 41.3%, 24.0% ,and 13.3% for WOG, Kedo SG Blue and K-file groups respectively. Regarding total number of crack in all sections, WOG showed statistically significant more dentinal cracks than Stainless steel hand k files (p<0.001), but no statistically significant difference with Kedo SG Blue.
The present study demonstrated that WOG was statistically a significant difference with ST.ST K-file in coronal and apical third (p<0.001), no statistically a significant in middle. Also, WOG was statistically a significant difference with Kedo SG Blue in middle third (p<0.001) , but no statistically a significant in coronal and apical third .
Kedo SG Blue showed no statistically a significant difference with stainless steel K-file in coronal and middle, but there was statistically a significant difference at apical part of the root (p<0.001).