In Vivo and In Vitro Effectiveness of Rotary Nickel-Titanium vs Manual Stainless Steel Instruments for Root Canal Therapy : Systematic Review and Meta-analysis

Introduction: This systematic review evaluated the effectiveness of nickel-titanium (NiTi) rotary files compared to stainless-steel (SST) hand files. Methods: An electronic search was performed on Medline, EMBASE, CENTRAL and Scopus databases up to February 2016. An additional hand searching was performed in 13 journals. The studies were classified according to study type and the outcome variables. Two reviewers independently applied eligibility criteria, extracted data, and three reviewers independently assessed the quality of the evidence of each included study according to The Cochrane Collaboration's procedures. A meta-analysis was performed whenever it was possible. Results: The electronic and hand search strategies yielded 1155 references of studies after removal of duplicates. Four clinical studies (two prospective and two retrospective studies) and 18 in vitro studies (on extracted teeth) were included for the qualitative synthesis after full-text evaluation of the eligible studies. The overall level of methodological quality of the studies included can be considered inadequate. Only one clinical study was judged at low risk of bias, whereas most non-clinical studies had a low risk of bias. Three meta-analyses, based on a very limited number of studies, could be performed. Each meta-analysis contained two studies. Of these, one meta-analysis was based on clinical studies. Conclusions: The results of this systematic review suggested that NiTi rotary instruments were associated with lower canal transportation and apical extrusion when compared to SST hand files, whereas both groups had similar outcomes in terms of success of therapy, amount of residual bacteria, and cleansing ability after treatment. However, due to the limited evidence available, these results should be interpreted with caution. Consequently, more randomized control trials using standardized protocols are needed in order to provide more solid recommendations.