Shaping efficiency of rotary and reciprocating kinematics of engine-driven nickel-titanium instruments in moderate and severely-curved root canals using micro-computed tomography: a systematic review of ex vivo studies.

INTRODUCTION: This systematic review aimed to compare reciprocating with continuous rotary instrumentation kinematics, by means of microcomputed tomography evaluations, in extracted human permanent teeth with moderate and severe canal curvatures. METHODS: The research protocol was registered in the International Prospective Register of Systematic Reviews and given the reference number CRD42023404035. An electronic search was undertaken in MEDLINE (PubMed), EBSCO, Scopus, Web of Science databases until December 2021. Manual screening of issues in endodontic journals and references of relevant articles were assessed individually. The risk of bias of the included articles was evaluated with the QUIN tool (Quality Assessment Tool for In Vitro Studies). RESULTS: Among 1640 retrieved articles, 49 were included in the qualitative synthesis. Fifteen articles had low risk of bias, 33 articles had medium risk of bias, and only 1 study was at high risk of bias. Continuous rotary systems had better centering ability in both moderate and severe canal curvatures and resulted in less apical transportation in severely curved root canals. None of the kinematic systems was capable of instrumenting the entire canal surface area. Reciprocating kinematics systems tended to provide higher increase in surface area of severely curved canals and produced fewer dentinal microcracks in moderately curved canals. CONCLUSIONS: The evidence presented in this review suggests that continuous rotary system seems to be better than reciprocating system in solving the major issues encountered during root canal instrumentation of extracted teeth with moderate and severe curvatures.