الفهرس 
ACKNOWLEDGEMENTSOnly 14 pages are availabe for public view
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Abstract
In the past decades, vertical root fracture was a common complication associated with mechanical preparation, leading to tooth loss. A crack or a craze line can propagate into root fracture if the tooth is subjected to repeated stress, therefore, currently the consensus is that such defects should be prevented.
The aim of this study was to evaluate dentinal defects formed using two single file systems (reciprocating and continuous rotation) versus manual instrumentation using cone beam computed tomography (CBCT).
Forty five mesial roots of mandibular first extracted molars were used in this study. The mesial root specimens were randomly divided into three groups of 15 teeth each, according to the type of instrument used; group (1): WaveOne primary file, group (2): One Shape file, group (3): K-Flexofiles. Evaluation of the incidence and size of dentinal defects originally present in the specimens was done for the full length of the root by CBCT.
In group (1), WaveOne primary file was used in reciprocating motion. In group (2), One Shape file was used in continuous rotation motion. While in group (3), step back instrumentation technique was carried out using K-Flexofiles. Evaluation of the incidence and size of dentinal defects formed after instrumentation was done for the full length of the root by CBCT.
The results were collected, tabulated and statistically analyzed and according to the results of this study, the formation of dentinal defects was observed in all groups. The highest number of dentinal defects was found in the continuous rotation group (One Shape), although no statistical significant difference was found between this group and both the reciprocating and the manual technique groups.