The influence of kinematics of engine-driven nickel-titanium instruments on root canal shape assessed by micro-computed tomography: a systematic review

Aim: To evaluate if the kinematics of engine-driven instruments affect the root canal shape. Method: The systematic review was registered in PROSPERO (CRD 42017077043). A broad search was performed for articles published before 26 September 2018 in the electronic databases: pubmed, scopus, web of science and Lilacs using MeSH and free terms. Only in vitro studies with human teeth that evaluated root canal shape by volume, surface area and unprepared surface area using reciprocating and rotary system assessed by micro-computed tomography were included. A modified checklist for randomized controlled trials from the Joanna Briggs Institute was used to assess the risk of bias. Results: Twenty-one articles were selected. According to quality assessment, all studies were considered 'moderate methodological quality'. Eighteen articles analysed volume increase, only four studies showed statistically significant difference, three indicating that the reciprocating movement obtained a greater increase in volume than the rotary system and one rotary system obtained a greater increase. Twelve studies analysed surface area, only three studies showed statistically significant difference, two presented a reciprocating system revealing greater amount of surface area and one showed a rotary system obtained a greater amount of surface area. Ten articles evaluated unprepared surface area, two studies that analysed total length, one study presented that the rotary system revealed lower unprepared surface area while another study showed reciprocating with less unprepared area. One study analysed middle and apical third, and observed that the rotary system presented lower unprepared surface area in the middle third. Conclusions: Both the rotary and reciprocating kinematics produce changes in volume and surface area and leave unprepared areas in the root canal, however reciprocating system showed greater increase of volume and surface area, while the rotary system maintains less unprepared surface area.