Introduction: All Instrumentation techniques have been reported to be associated with extrusion of infected debris. The aim of this study was to evaluate the number of bacteria extruded apically from extracted teeth ex vivo after canal Instrumentation using the two engine-driven techniques utilizing nickel-titanium instruments (Flex Master and M two).Materials and Methods: Seventy extracted maxillary central incisor teeth were used. Access cavities were prepared and root canals were then contaminated with a suspension of Enterococcus faecalis and dried. The contaminated roots were divided into two experimental groups of 30 teeth each and one control group of 10 teeth. Group I, Flex Master; Group2, M two; Group 3, control group: no Instrumentation was attempted. Bacteria extruded from the apical foramen during Instrumentation were collected in to vials. The microbiological samples from the vials were incubated in culture media for 24 h. Colonies of bacteria were counted and the results were given as number of colony-forming units. The obtained data were analyzed using the Kruskal-Wallis one-way analysis of variance and Mann-Whitney V-tests, with a = 0.05 as the level for statistical significance.Results: Findings showed that there was no significant difference as to the number of extruded bacteria between two engine-driven systems (P>0.05).Conclusion: Both engine-driven Nickel-Titanium systems extruded bacteria through the apical foramen.

Introduction: The objective of this in vitro study was to evaluate whether cervical preparation with Mtwo files in a crown-down technique influences Instrumentation time and the cyclic fatigue resistance of these instruments. Methods and Materials: Two Instrumentation techniques were evaluated (manufacturer and crown-down). Each group consisted of 10 kits containing four Mtwo instruments (10/0. 04, 15/0. 05, 20/0. 06, and 25/0. 06), which were used to prepare three standard simulated curved resin canals. The mean Instrumentation time and the corresponding number of cycles for each Instrumentation (NCI) were recorded. The instruments were rotated at a constant speed of 300 rpm in a stainless-steel canal (diameter of 1. 5 mm) at a 90° angle of curvature and 5-mm radius. The center of the curvature was 5 mm from the tip of the instrument. The cyclic fatigue resistance of the files was determined by counting the number of cycles to failure (NCF). Data were analyzed by the Mann-Whitney test. Results: The mean Instrumentation time and NCI of files 10/0. 04 and 15/0. 05 were significantly lower (P<0. 05) when the crowndown technique was used compared to the manufacturer’ s method for the same tip size/taper file. There was no significant difference in the mean NCF between the two techniques. Conclusion: The crown-down technique did not interfere with resistance to cyclic fatigue. However, the shorter Instrumentation time of files 10/0. 04 and 15/0. 05 could reduce the fracture risk in the case of reuse of these instruments.

Introduction: Pulpectomy of primary teeth is commonly carried out with hand files and broaches; a tricky and time consuming procedure. The purpose of this in vitro study was to compare the cleaning efficacy and time taken for Instrumentation of deciduous molars using hand K-files and Flex Master Rotary system.Materials and Methods: In this study, 68 canals of 23 extracted primary molars with at least two third intact roots and 7-12 mm length were selected. After preparing an access cavity, K-file size #15 was introduced into the root canal and India ink was injected with an insulin syringe. Sixty samples were randomly divided in to experimental groups in group I (n=30), root canals were prepared with hand K-files; in group II (n=30), Rotary Flex Master files were used for Instrumentation, and in group III 8 remained samples were considered as negative controls. After clearing and root sectioning, the removal of India ink from cervical, middle, and apical thirds was scored. Data was analyzed using student's T-test and Mann-Whitney U test. Results: There was no significant difference between experimental groups cleaning efficacy at the cervical, middle and apical root canal thirds. Only the coronal third scored higher in the hand instrumented group (P<0.001). Instrumentation with Flex Master Rotary files was significantly less time consuming (P<0.001).Conclusion: Although there was no difference in cleanliness efficacy at the apical and middle thirds, the coronal third was more effectively cleaned with hand files. Predictably, time efficiency was a significant advantage with Rotary technique.

Introduction: To compare the cleaning effectiveness of K3 and Race NiTi Rotary systems with K-Flexo file instruments during the preparation of curved canals in extracted human teeth.Materials and Methods: A total of 50 root canals of mandibular and maxillary molars with curvatures ranging between 25o and 35o were divided in three groups of 15 each and 5 as negative control groups. Canals were prepared using a low torque control motor in two Rotary groups according to manufacturer's instructions. Conventional Step back with S.S K-files was the preparation technique in third group. The amount of debris and smear layer was quantified on the basis of a numerical evaluation scale. The data were statistically analyzed using Chi- Square and Likelihood Ratio tests.Results: In general, no significant difference in terms of amount of debris were found among three groups, only in apical zones of Race and K-Flexo file groups a significant difference was detected (P=0.041). Race Rotary system left significantly less smear layer than K-Flexo file in the middle (P=0.009) and apical thirds (P=0.012), respectively. K3 significantly achieved higher scores of cleanliness than K-Flexo file in apical third only (P=0.049).No significant difference between Race and K3 Rotary groups for residual debris and formed smear layer was detected.Conclusion: Obtaining higher scores of cleanliness in various regions of the canals, crown down technique and the use of Rotary Instrumentation seem to be superior to conventional hand Instrumentation with step back technique .No significant difference between K3 with three radial lands and Race with three cutting edges in terms of debris and smear layer formation was detected.

Background. This study compared apical extrusion of debris and Instrumentation time following root canal Instrumentation with Reciproc, Reciproc Blue, and Gentlefile (GF) Rotary instruments versus the manual step-back technique. Methods. This in vitro study was conducted on 80 extracted mandibular premolars with mature apices and a root curvature of<10º. The teeth were randomly assigned to 4 groups (n=20), standardized regarding working length, and placed in pre-weighed vials. The root canals were instrumented with Reciproc, Reciproc Blue, and GF systems and the manual step-back technique in the four groups. The vials containing the collected debris were then dried and weighed. The Instrumentation time was also recorded for each group. Data were analyzed with one-way ANOVA and post hoc Games-Howell test (α=0. 05). Results. Minimum apical debris extrusion was noted in Reciproc, followed by Reciproc Blue, GF, and manual technique (P<0. 05). Pairwise comparisons showed significantly lower apical extrusion of debris in the Reciproc compared with GF (P=0. 015) and manual Instrumentation (P=0. 011) groups. The Reciproc system also had the shortest Instrumentation time, followed by Reciproc Blue, GF, and manual Instrumentation (P<0. 05). Pairwise comparisons showed significant differences between all the systems (P<0. 05) except between Reciproc and Reciproc Blue (P>0. 05) in this respect. Conclusion. Although all systems caused apical extrusion of debris, manual Instrumentation caused maximum extrusion of debris. In contrast, the Reciproc system was superior to others regarding minimal apical extrusion of debris and the shortest Instrumentation time.

Introduction: Use of Rotary files in root canal preparation is inevitable due to their high speed and reduced duration of treatment. However, microcracks and even root fracture may sometimes occur in teeth where canal(s) is/are prepared using these devices. The purpose of the current study was to compare NeoNiti single-file with RaCe multi-file Rotary systems. Materials and Methods: An accurate scanner designed detailed three-dimensional file models, and a simulated model was developed using canal-specific features; including dentin thickness, root canal length, taper rate and root canal curvature. Cleaning and shaping conditions were simulated with appropriate speed and crack conditions for both types of files on the computer. Strain accumulation sites in the root dentin wall where microcracks was likely to occur were simulated and investigated. Abaqus and ANSYS software were used to perform finite element simulations. Results: RaCe files with 0. 04 taper caused the lowest level of stress (34. 33 MPa) to the simulated canal. Conversely, the highest level of stress (62. 35 MPa) was applied by 8% NeoNiti file to the simulated canal. Conclusions: Based on the present experimental study, it can be concluded that RaCe multi-file Rotary system may better be used in endodontic therapy, and the risk of microcracks in the tooth wall is less than that of NeoNiti single-file Rotary system.

Background and Aim: Pulpectomy of primary teeth is commonly performed with hand files and instruments. However, it is a time consuming procedure. Compared to hand files, Rotary Instrumentation has more advantages. The purpose of this in vitro study was to compare the cleaning efficacy and time taken for Instrumentation of deciduous molars using Reciproc and Mtwo Rotary systems. Materials and Methods: In this experimental study, 96 canals of 28 extracted primary molars with at least two-thirds of intact roots, with no previous treatment and 7-12 mm length were selected. After access cavity preparation, size #15 K-file was introduced into the root canal and India ink was injected with an insulin syringe. Then, 96 samples were randomly divided into two experimental groups and one control group. In group I (n=44), root canals were prepared with Reciproc; in group II (n=44), Mtwo files were used for Instrumentation, and in group III, eight samples were considered as negative controls. After clearing and root sectioning, the removal of India ink in the cervical, middle, and apical thirds was scored. Data were analyzed using Student's t-test and Mann-Whitney U test. Results: There was no significant difference between the experimental groups regarding cleaning efficacy at the apical third of root canals (P>0. 05). The coronal and middle thirds scored higher in the Reciproc group (P<0. 05). Instrumentation with Reciproc Rotary files was significantly less time consuming (P<0. 001). Conclusion: Using new systems such as Reciproc file for pulpectomy of primary teeth is beneficial.