The active vibration control of a smart cantilever Rotary Beam, using dual sensor and actuator piezoelectric patches stuck on the outer surface of the Beam, is studied. Motion equations are discretized by finite element method with 6 and 9 DOF elements for parts without piezoelectric patches and with them, respectively. Several types of controllers such as LQR, LQG and rate feedback controller are employed to actively control vibrations of the Beam. Simulation results exhibit a better performance in terms of settling time for the LQR controller due to all states’ feedback; while rate controller is only relying on the sensor patches for feedback which is convenient in terms of cost. Also, the effect of the number of piezoelectric patches is studied.

Background and Aim: Maintaining the original shape and path of the canal is among the most important criteria for optimal root canal preparation. The aim of this study was to compare the centering ability of F6 SkyTaper and RaCe Rotary files in mesiobuccal canals of mandibular molars. Materials and Methods: In this experimental study, 30 mesiobuccal canals of extracted human mandibular molars with 25-30-degree curvature were randomly divided into two experimental groups (n=15) of RaCe and F6 SkyTaper. After mounting of the teeth in a putty mold, the distance between the canal walls and the outer surface of the roots in mesial and distal aspects was measured. The measurements were made at 1, 3 and 7 mm from the apex. Initial glide path in the canals was achieved using a # 15 K-file. Then, the canals in group A were prepared by RaCe Rotary file #25/6% while the canals in group B were prepared by F6 Sky Taper Rotary file #25/6%. Measurements were repeated and the difference between the two measurements was calculated and compared with the Mann-Whitney U test. Results: The mean centering ability was 0. 72 ±,0. 62 in the RaCe group and 0. 95 ±,1. 39 in F6 SkyTaper group. the centrality was better in F6 SkyTaper group (it was closer to 1) but the difference was not statistically significant (P=0. 4). Conclusion: Both RaCe and F6 SkyTaper Rotary systems partially offset the centrality of the root canal system.

The free vibration analysis of rotating functionally graded (FG) nano-Beams under an in-plane thermal loading is provided for the first time in this paper. The formulation used is based on Euler-Bernoulli Beam theory through Hamilton’ s principle and the small scale effect has been formulated using the Eringen elasticity theory. Then, they are solved by a generalized differential quadrature method (GDQM). It is supposed that, according to the power-law form (P-FGM), the thermal distribution is non-linear and material properties are dependent to temperature and are changing continuously through the thickness. Free vibration frequencies are obtained for two types of boundary conditions; cantilever and propped cantilever. The novelty of this work is related to vibration analysis of rotating FG nano-Beam under different distributions of temperature with different boundary conditions using nonlocal Euler-Bernoulli Beam theory. Presented theoretical results are validated by comparing the obtained results with literature. Numerical results are presented in both cantilever and propped cantilever nano-Beams and the influences of the thermal, nonlocal small-scale, angular velocity, hub radius, FG index and higher modes number on the natural frequencies of the FG nano-Beams are investigated in detail.

Background and Objective: The preparation of the root canal (i. e., cleaning and shaping) is the main step in the endodontic treatment. The nickel-titanium Rotary files result in fewer errors during the preparation of curved canals. This study aimed to compare the transportation of Neolix and Reciproc Rotary systems in curved canals using cone Beam computed tomography (CBCT). Materials and Methods: In this experimental study, 70 extracted curved premolar teeth from patients referred to dentistry faculty were assigned into two groups (n=35). The preparation of the canals was performed by the Neolix and Reciproc Rotary systems. Remaining dentin thickness, transportation, and canal-centering ratio were evaluated and compared using CBCT images before and after the instrumentation. The data were analyzed in SPSS software (version. 19) through ANOVA, independent t-test, and paired t-test. Results: There was a significant difference in terms of remaining dentin thickness in three sections of 3, 5, and 7 mm from the apex, before and after the instrumentation regarding the level of mesiodistal and buccolingual. However, no significant difference was observed in terms of the transportation in three sections of 3, 5, and 7 mm from the apex in both Neolix and Reciproc systems. Conclusion: According to the results, both Neolix and Reciproc Rotary systems showed high efficacy in root canal shaping. The amount of transportation in these systems during preparation of curved canals was very low leading to the protection of canal-centering ratio.

Original Article Introduction: The aim of this in vitro study was to evaluate the transportation of mesiobuccal canals of mandibular first molars prepared with either BioRaCe or Mtwo Rotary instruments or hand K-Flexofile, by means of cone-Beam computed tomography (CBCT).Methods and Materials: Forty-five mandibular molars were selected and randomly divided into three groups (n=15). Mesiobuccal roots of these teeth were prepared by BioRaCe, Mtwo, or hand K-Flexofile. Transportation was measured by pre- and post-operative CBCT images. Two-way ANOVA analysis was applied to detect any differences between the groups followed by the post hoc Tukey’s tests. The level of significance was set at 0.05.Results: The non-parametric Friedman test was used to compare the behavior of each file at 3-, 6- and 9-mm levels. There were no significant differences between different levels in Mtwo group (P=0.15); however, the differences in K-Flexofile and BioRaCe groups were significant (P>0.05). The post hoc Tukey’s test revealed significant differences between BioRaCe and K-Flexofile and also between Mtwo and K-Flexofile, both in the 3-mm depths (P<0.05).Conclusion: Under the limitations of the present study, BioRaCe and Mtwo Rotary instruments are considered suitable for canal preparation to greater apical sizes provided that the recommended sequences are observed.

Statement of Problem: Total removal of tissues and remnant microorganisms as well as canal shaping is the essential objectives of endodontic therapy. A successful endodontic treatment is obtained through Shilders principals, however; complete observation of this technique using stainless steel files manually is problematic and time-consuming. Modern technology, in order to eliminate such problems, has presented new facilities such as Nickel-Titanium (NiTi) files and engine driven instruments.Purpose: The aim of this in-vitro study was to compare the canal debridement efficiency of three engine driven instruments: Rotary, Reciprocal and Vertical.Materials and Methods: In this experimental study, 60 mesial roots of human first and second mandibular molars were divided into three groups randomly. In each sample, one canal was considered as case, the other one as control. Files used in Reciprocal and vertical groups were of handy Ni-Ti type and in Rotary group, Rotary Ni-Ti files were used. After debridement, the roots were sectioned at 3mm and 5mm from anatomic apex, stained and examined under light microscope. Comparison criteria between case and control groups were based on residual debris and predentin and the level of root canal preparation and shaping after debridement. Data were subjected to kruskal-Wallis non-parametric test.Results: There was no significant difference between the efficiency of debridement at 3mm and 5mm sections between all groups. But difference in time consumption was significant ranked from the shortest to the longest as Rotary, reciprocal and vertical.Conclusion: The efficiency of debridement between the three automated instruments was approximately equal, however; the instrumentation time was different between three groups. Rotary system was the fastest one, as compared with reciprocal (second) and vertical (last). It may be concluded that Rotary system has a superiority over the other two groups in conventional root canal therapies.

In this paper, vibration analysis of multiple-stepped Bernoulli-Euler and Timoshenko Beams carrying point masses is presented analytically for various boundary conditions. Each attached element is considered to have both translational and rotational inertias. The method of solution is “transfer matrix method” which is based on the changes in the vibration modes at the vicinity of any discontinuity in geometrical and natural parameters; these changes are shown by transfer matrices depended on the geometry of each step or value of the translational and rotational inertias of each attached element. First, natural frequencies and corresponding normal mode shapes are obtained by implementation of the compatibility conditions and external boundary conditions; Then, the precision of the proposed method is checked by comparison of the results with other exact solutions; Finally, the effect of the translational and rotational inertias and position of the attached elements on the natural frequencies of multi-stepped Beams are investigated for various boundary conditions.

Background and Aim: This study evaluated the remaining dentin thickness (RDT), canal transportation (CT), and canal centering ratio (CCR) of three different Rotary file systems using cone-Beam computed tomography (CBCT).    Materials and Methods: In this in vitro study, 153 extracted mandibular molars were evaluated. The working length was determined using CBCT before starting the experiment. A skilled dentist then prepared the root canals using three types of Rotary files: ProFit S3, HyFLEX CM, and NeoEndo S. Pre- and post-treatment CBCT scans were analyzed to compare the results. One-way ANOVA and Tukey test were used for statistical analysis.    Results: ProFit S3 demonstrated a superior performance in preserving dentin thickness and maintaining canal geometry compared to HyFlex CM and NeoEndo S. In both MB and ML canals, at 6 mm and 9 mm, ProFit S3 exhibited significantly higher RDT (P≤0.007), less CT (P≤0.006), and better CCR (P≤0.01) than other systems. Among the remaining systems, HyFlex CM performed better than NeoEndo S for RDT and CT at these levels. At 3 mm, no significant differences were found for RDT or CT; however, ProFit S3 showed significantly better CCR than NeoEndo S (P<0.01) and HyFlex CM (P<0.05). Conclusion: Among the tested systems, ProFit S3 resulted in the least change in canal volume, suggesting that it may be better at preserving the original shape of the root canal, as well as the surrounding dentin, compared to Hyflex CM and NeoEndo S.

Background and purpose: The purpose of mechanical cleaning of the root canal is to clean the canal walls, create a conical shape to facilitate access, effective washing, and filling all areas of the root canal. Errors such as root canal transportation are cuased by excessive dentin removal from the canal. The objective of this study was to investigate root canal transportation by a BT Race Rotary and manual file with Cone Beam Computed Tomography (CBCT). Materials and methods: An Ex-vivo study was conducted in 54 extracted first molars. Root curvature was measured by Schneider's method. Preparation was performed in two groups (n= 27 per group) with manual and Rotary files. CBCT images were prepared pre and post instrumentation of the canals. SPSS 18 Software was used to measure the amount of canal transportation. Results: The mean differences of canal transportation between the two groups were 0. 24 ± 0. 16, 0. 19 ± 0. 13mm, and 0. 17± 0. 12mm at T1 (1 mm from apical foramen), T2 (2 mm from apical foramen), and T3 (3 mm from the apical foramen), respectively. The total deviation was 0. 022mm in this study. The Rotary and manual files at T1 (P=0. 51) and T3 (P=0. 57) were not significantly different in causing transportation but T2 was found to cause significant canal transportation (P=0. 027). Conclusion: The average canal transportation in 2mm canal from the apical foramen by manual files was lesser than the Rotary files. BT race and K-flexo file instruments can preserve the curvature of the root canals. Therefore, both systems can be used in clinical settings with minimal apical transportation.