The influence of plug shape on the performance of an aerospike nozzle thrust force is studied in different back pressure conditions. To generate smooth plug contours, Cubic B-Spline technique is employed. In the current research, basis functions are obtained using Deboor’ s relation. The flow field around the aerospike nozzle is investigated implementing various shapes, and the best of the generated configurations is determined. The flow field is simulated using Navier-Stokes equations and k-ε turbulence model. A triangle unstructured grid is applied for discretization of the governing equations. The computational methodology utilizes steady state density-based formulation, and a finite volume cell centered scheme is used to discretize the flow field equations. The flow field is divided into several zones to accelerate the solution convergence, , and an appropriate initial condition is assigned to each zone. Six different shapes of the plug are generated, and the effect of the spike shape on the formation of the shock and expansion waves is investigated in each case. The thrust force is calculated for each case, and the best configuration is determined in terms of the maximum thrust generation. Eventually, the temperature distribution is calculated along the nozzle for further investigations, and it is concluded that the best configurations show a lower temperature rise compared to other designs.

Managing of necrotic permanent teeth with immature apices is a treatment challenges. Treatment of such teeth includes apexification, apical plug and more recently, revascularization technique with the probable advantage of continuation of root development. In the present case report the referred patient had discomfort with a necrotic immature mandibular first molar. Periapical radiography showed a rather large apical lesion around immature roots. Revascularization protocol using calcium-enriched mixture (CEM) cement was indicated for the mesial root. However, in distal canal apical plug technique was applied. At 2-year followup, both procedures were successful in relieving patient’ s symptoms. Dentin formation and increase in length of the mesial root was obvious. Apical plug and revascularization technique proved to be successful in management of necrotic immature teeth; moreover, revascularization carried the advantage of continuation of root development.

In this research work a shape from shading (SFS) technique which incorporates a Lambertian model is implemented for the automatic generation of a digital terrain model (DTM) using a single view aerial image. The developed algorithm is tested on both simulated and real data. The estimated accuracy of the generated DTM from the simulated data, which has a bilinear surface, is about ±3 cm. The real data is a scanned aerial photograph taken over a low texture hilly terrain. The generated DTM by the SFS technique is compared with a DTM acquired by the manual measurement of the stereo image of the same area using a photogram metric plotter. The estimated rimes of the discrepancies between the grid nodes of the measured and the automatically generated DTM is about ±4 meters. The unsuccessful reconstruction of the terrain surface for the real data is due to the fact that a simple Lambertian model does not take into account, in a perfect way, different nondeterministic influential factors such as the terrain alb Edo variations and the random noise. The influence of the latter case was reduced by a low pass filter applied as a preprocessing stage.

Background & Aim: Extrusion of debris from apex is one of the main factors of flare up (inflammation, pain or combination of both). Various studies have been conducted toward the amount of debris extrusion but no one compared this drawback on one – shape and xp-shaper system in curved root canals. So, this study aimed to determine the amount of apical debris extrusion following preparation of canal by one-shape or xp-shaper in curved canals of mesiobuccal root in mandibular first molars.Material & Method: This experimental study was done on 34 mandibular first molars with 30 to 40 degree curved mesiobuccal root canal. The samples were randomly divided in two groups. First group had one –shape for root canal preparation while the other had xp-shaper. Roots of the teeth were fixed in pre weighted fluxes till cervical area so that all apical debris were collected in vials. After desiccation process, the vials were weighted again. The difference between original and secondary weight of vials containing debris is considered as weight of debris extrusion. Data were analyzed using T-test.Results: Amount of debris extrusion in one– shape group was 0.018±0.014 and in xp-shaper group was 0.01±0.007 and the difference was statistically significant (0.01).Conclusion: Considering the situation and limitation of this in vitro study, xp-shaper rotary system was associated with less debris extrusion compared to one – shape systems.

The classification of shape data is a significant challenge in the statistical analysis of shapes and machine learning. In this paper, we introduce a multinomial logistic regression model based on shape descriptors for classifying labeled configurations. In this model, the explanatory variables include a set of geometric descriptors such as area, elongation, convexity, and circularity, while the response variable represents the category of each configuration. The inclusion of these descriptors preserves essential geometric information and enhances classification accuracy. We evaluate the proposed model using both simulated data and real datasets, and the results demonstrate its effective performance. Additionally, the proposed method was compared with one of the existing methods in the literature, and the results indicated its superiority in terms of both classification accuracy and computational simplicity.

Statement of problem: Management of open apices teeth is one of the most serious problems for dentists. Contemporary endodontics proceeds to single step techniques such as apical plug and customized cone for management of these cases.Purpose: The purpose of this study was to compare apical micro leakage between customized cone and apical plug techniques on open apices polyester made root canals.Materials and methods: In this in vitro experimental study, 68 clear models were made from polyester in two different forms: S models (round canals), and L models (oval canals). Thirty models (15 S and 15 L) were obturated with customized cone technique and 30 models (15 S and 15 L) were obturated with apical plug technique using Ca (OH)2 as an apical barrier. Eight models were considered as positive and negative control groups. Models were immersed in methylene blue for 48 hours and maximum linear dye penetration of each was measured by three separate observers. Student t test was used for statistical analysis of the findings.Result: The results illustrated that the mean leakage of the customized cone group was statistically greater than apical plug group (p<0.05). In addition, when comparing L and S models in customized group, L models showed more linear leakage than S models (p<0.05), but this difference was not significant in apical plug technique.Conclusion: The finding of this study indicated that the apical plug technique, when using Ca (OH)2 plug as a barrier may produce a better apical seal than the customized cone technique in short term.

The tissues in the human body comprise complex assemblages of several different types of cells that are dispersed on an extracellular matrix (ECM). In addition to biochemical and chemophysical factors, dynamic changes in the mechanical-structural properties of ECM lead to changes in cell behavior such as proliferation, differentiation, and its nature. Since any activity of the cells takes place on a dynamic substrate in the body, it is necessary to provide conditions in which the dynamic environment inside the body can be simulated. Therefore, researchers need intelligent biomaterials that can act as a powerful substrate to design smart cell culture platforms and tissue engineering scaffolds, as well as to simulate this complex environment. Shape memory polymers (SMPs) and shape-changing polymers (SCPs) are the new generations of intelligent materials that can be converted from shape A to shape B in a response to a stimulus, creating new mechanical and structural properties. Although tissue engineering studies on static substrates have been performed so far, it is now clear that the fate of cells in proliferation and differentiation is influenced by the dynamic conditions of the environment. However, recent studies have been focused on designing new substrates to mimic the dynamic microenvironment. In this review article, a brief definition of cell mechanobiology is introduced and then the recent advances in the design of SMPs and SCPs used in fundamental cell mechanobiology studies were highlighted. A survey of the current review can create a more innovative perspective for researchers in this field.

Introduction: The aim of this study was to assess the fracture strength of immature single-rooted teeth restored with fiber post and apical plug.Materials & Methods: In this experimental study, fifty mandibular premolars were divided into five groups. The coronal and apical portions were cut to obtain15±1 mm root lengths and cleaning& shaping were performed. Peeso reamer #4 was passed the apex by 1 mm to simulate an immature tooth and the apical portion in group 1 to 5 was filled by lateral compaction of 5 mm of guttapercha; 5 mm of mineral trioxide aggregate (MTA); 5mm of calcium enriched mixture (CEM) cement; 3 mm of MTA and 2 mm of gutta-percha by vertical condensation and 3 mm of CEM cement and 2 mm of gutta-percha, respectively. The remaining portion was restored with glass fiber post and self-etch cement and composite cores were built. Compressive load was applied at a crosshead speed of 1 mm/minute at 90o angle until fracture in a universal testing machine. Data were analyzed using ANOVA in SPSS16.Results: The mean±SD fracture strength was recorded 607.8±162.41 N, 700.48±183.24 N, 595.16±171.77 N, 886.36±382.92N, and 868.87±440.36 N in groups one to five, respectively. No significant difference was observed among the experimental groups (p=0.1).Conclusion: In immature teeth requiring an apical plug, fiber post can be placed directly on the MTA and CEM apical plugs and there is no need for placing gutta-percha on the plug.