This study evaluates the effectiveness of different activated irrigation techniques on removal of debris and smear layer from curved root canals. Ninety mandibular molars with a root canal curvature between 20 and 40 degrees were assigned to 4 groups (n = 20): syringe irrigation (SI), passive ultrasonic activation (PUI), sonic activation with EDDY (ED) or EndoActivator (EA) and a control group. Mesiobuccal root canals were prepared to size 40, 0.04 and irrigated with NaOCl (3%) according to the respective technique. Roots were split longitudinally and subjected to scanning electron microscopic analysis. Presence of debris and smear layer was evaluated using 5-grade scoring systems with 2009 and 10009 magnification, respectively. Data were analysed with nonparametric analysis for ordinal longitudinal data (a = 5%). Activation of the irrigant significantly improved smear layer removal (P < 0.05). Regarding debris, only activation with EA and ED was significantly more effective than SI (P < 0.05). No activation technique was able to eliminate debris and smear layer completely from curved root canals.
This study evaluates the effectiveness of different techniques to remove fibre posts from root filled teeth in vitro. One hundred and fifty-three extracted single-rooted teeth were decoronated, root-canal treated and divided into three groups (n = 51). Post spaces were prepared for different types of fibre posts: glass fibre, quartz fibre, carbon fibre. Each group was divided into three subgroups with regard to the post removal technique (n = 17): SonicFlex Endo, long-shaft round bur, DT-Post removal kit. Residual material, loss of dentine, working time and procedural errors were assessed using computed tomography. Statistical analysis was performed with a one-way anova (α = 0.05). The highest effectiveness was achieved with the sonic tip and the round bur. A high prevalence of perforations or severe deviations from the root axis was observed for all groups. No technique presented favourable results in all assessed parameters. There is a high risk of perforations.
Moisture content of dentine influenced detection of microcracks when evaluated using micro-CT. Scanning should be performed on dried specimens to allow reliable identification of dentinal defects. Formation of new cracks during dry periods up to 24 h was disproved.
All authors have contributed significantly and are in agreement with the manuscript.
AbstractThis study evaluated the effect of three different NiTi instrumentation techniques on the incidence of microcracks after the preparation of straight and curved root canals using micro-CT. Roots from mandibular premolars and maxillary molars (n = 66) with the same mean canal curvatures were assigned to three groups of straight and three groups of curved roots (n = 11). After preoperative micro-CT scans, root canals were prepared with Reciproc, OneShape and ProTaper Next to size 25. Specimens were scanned again, and pre-and post-operative cross-sectional images (n = 75 263) were screened to identify the presence of dentinal microcracks. Overall, microcracks were detected in 2.97% (n = 2236) of the cross-sectional images. No new dentinal microcracks were observed after root canal instrumentation of straight and curved canals with the tested NiTi systems. Instrumentation with Reciproc, OneShape and ProTaper Next did not induce the formation of dentinal microcracks irrespective of canal curvature.
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