Ramy El-saadany, MuhammedOsama,AmroAbdul Razekm Abstract: Introduction: The aim of the current study was to evaluate and assess the changes in root canal morphology after instrumentation with XP endo shaper, HyFlex cm and Sendoline S5 sing cone beam computed tomography (CBCT). Methods: forty five mesiobuccal canals from mandibular first molar were matched anatomically using (CBCT) and distributed into 3 homogeneous groups (n = 15) according to the canal preparation protocol. Reregistered images, before and after preparation, were evaluated for the canal surface area and roundness. Data were statistically compared between groups using the one-way analysis of variance post hoc Tukey's post hoc test and within groups with the paired sample t test (a = 5%). Results: no important statistical differences among the three groups before instrumentation After preparation protocols, changes in area and roundness of the root canals showed no difference between groups (P >0.05) Conclusions: The XP endo Shaper, Hyflex cm, and Sendoline S5 systems showed a similar ability to maintainroot canal roundness.