Abstract
The effect of root canal preparation technique on microcrack initiation is a controversial issue. This systematic review aimed to assess the role of root canal preparation techniques with different kinematics (manual, rotary, reciprocating, adaptive, self-adjusting file) on microcrack initiation. In vitro and in situ studies comparing the influence of at least two different root canal preparation techniques on the initiation of dentin microcracks were searched in PubMed/MEDLINE and SCOPUS up to June 5, 2018 without language and period restriction. Two authors independently reviewed all identified titles and abstracts for eligibility. Tables were generated to summarize the included studies, and the included studies were assessed for bias. Fifty-four (n=54) articles met the eligibility criteria. The results were classified according to the method used for microcrack evaluation, and most studies that used micro-computed tomography showed no formation of new cracks after root canal preparation. In general, the instrumentation techniques induced microcrack formation when the methods were destructive, irrespective of kinematics. In relation to the apex region, when the preparation working length was set as the root canal length subtracted of 1 mm, the risk of microcrack initiation reduces. The majority of the included studies had low risk of bias for all assessed domains. Our results seem to indicate that the various root canal preparation techniques considered in this study will not cause damage to the dental structure when adequately employed and the proper methodology is applied.
Highlights
Hand root canal preparation techniques were successfully employed for many years, with advances leading to alternative mechanized systems that employ different kinematics, optimizing the procedure, enhancing shaping ability and decreasing the risk of instrument fracture during treatment (1,2)
The results were classified according to the method used for microcrack evaluation, and most studies that used micro-computed tomography showed no formation of new cracks after root canal preparation
Seven studies (63.64%) demonstrated no formation of new cracks after root canal preparation (9-12,24,28,33), and the following studies revealed formation of new cracks after root canal preparation: Li et al (49) showed that the OneShape system resulted in increased microcracks; Ceyhanli et al (30) compared two rotary systems (ProTaper Universal and RaCe) and one reciprocating system (Safesider) and the results revealed that all systems increased the number of microcracks, and ProTaper Universal generated more microcracks than the RaCe system; Pop et al, (55) tested ProTaper Universal and WaveOne and both systems induced microcracks
Summary
Hand root canal preparation techniques were successfully employed for many years, with advances (e.g. development of nickel–titanium instruments) leading to alternative mechanized systems that employ different kinematics, optimizing the procedure, enhancing shaping ability and decreasing the risk of instrument fracture during treatment (1,2). Kinematics of engine-driven Ni-Ti (nickel–titanium) instruments may be divided into rotary motion, rotational reciprocating motion, vertical vibration (Self-adjusting File system based on in-and-out motion to remove dentine and provide continuous irrigation during preparation), and rotary motion plus rotational reciprocating motion (adaptive motion) (3). Considering that these systems are operated under different kinematics and parameters of use, these factors may potentially influence the efficacy of the instrumentation and its impact on the final performance of endodontically treated teeth. A systematic review that considers all existing evidence on such scientific field may help to clarify such causal relation or guide future studies to adequately answer such important question
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