Changes of up to 80°C has been reported for oral cavity temperature. This could well effecti on the nature of restorations for example failure of bonding of adhesive restorations. It is advocated that using opaque layer in porcelane to restorations could reduce this problem. This experimental study was designed to evaluate the effect mentioned using finitelement analysis method.Results showed that cooling has a more destructive effect than warming process restorations with the presence of opaque having a finitelement analysis effect on restorations.

Background and Aim: The movement of molars has been evaluated in many studies to correct Cl II malocclusion by non-compliance appliances but the results are controversial. The aim of this study was to compare the upper first and second molars' movement in cervical headgear (HG) and pendulum appliance (PEND) by finite element method.Materials & Methods: For modeling process, one of the best dry skulls was CT scanned (l mm slices). Modeling was done according to the mechanical properties of cortical and trabecular bone of maxilla and PDM and teeth and transferred to computer by scanner. Elementing, meshing and loading was done. The magnitude of force for both appliances was 250 gr and line of force for HG was 20 degree above the occlusal plane action and for PEND was along the midlingual surface of upper first molar crown. Tooth movement analysis was performed by the software named Ansys 5.71.Results: The amount of dislocation of the 1st molar cusps tip (mesiobuccal, mesiopalatal, distobuccal, distopalatal) at presence of second molar in bucco-lingual dimension showed distal-in rotation in HG and mesial-in rotation for pendulum. In mesio-distal dimension, the four cusps of 1st molar moved distally in HG and palatal cusps moved more in PEND. In vertical dimension, 1st molar showed extrusion in HG and intrusion in PEND for distal cusps.Conclusion: The presence of second molar had impact on the quality of upper first molar in both appliances and it moved in a distal direction, extruded and buccal drifted in both of them. Therefore, with regard to the cooperation of the patients, pendulum appliance is recommended to correct Cl II malocclusion instead of cervical headgear.

Background: Since three decade ago, the application of the concept of finite element analysis (EEA) have received a keen interest among dental investigators. In practice the FEA provides detailed stress information regarding to a non-homogenious body such as craniofocal skeletal growth, tooth post ceramo-metal crowns and etc. The aim of this study was the determination of the influence of stress distribution at the cement interface of metal ceramic restoration-dentin. Materials and Methods: An idealized metal-ceramic crown model was developed. The model was divided into very small segments. Various loading conditions was applied to the model. A super sap software was used for analyzing the stress distribution. Results & Conclusion: The results of this study suggest that the higher shear stress was developed in the cervical region by two dimensional methods.

Background and Aim: Considering the importance of the design of framework in the stress distribution and probability of creating initial cracks in connectors region, proper design of framework is considered as a requirement. For this purpose, in order to examine the stress distribution in two designs of straight and curved framework, comparison was made using FEM method.Materials and Methods: Research using a descriptive method of FEM was performed. A laboratory prototype was produced and was scanned in a digital form, using CMM equipment by the laboratory and a super spot from the geometry of the part was created. The super spot was transformed to a 3D solid model by utilizing Catia software. The above model was divided into a high number small elements, using Meshing method, by Abaqus software to analyze the finite elements. Afterwards, by Boundary Condition definition, the part was ready to be analyzed. The mechanical properties of Zirconia was entered into the software in the form of a table. Reviewing stress distribution in the bridge specially with the stress on connectors region was performed. Three vertical loading models for each part were applied in central and distal Fosa and analyzed separately.Results: In this study, the findings were described in the form of Von mises stress in Mpa scale. The stress in the Curved model was more than the Straight model. As a result, the stress distribution is more desirable.Conclusion: According to the results of this study, the straight model showed a more desirable stress distribution compared with the curved model. However, it should be noted that these results were obtained in F.E. environment.

Background and Aim: Since today using dental implants which be substituted destroyed teeth is completly effective and current. The researchers make effort in design and making new generation of implants for having mere resistance against applied forces. This research has evaluated the pattern of horizontal and vertical forces distributed in implants with or without microthread using finite elements method.Materials and Methods: We have used the developed software Ansys 11 for modeling, applying forces and stress distribution evaluation. Cortical and Spongy bone in the limitation of implant with natural dimensions were modelled. In this research Superline and Implantium implant systems with the diameter of 4.3 mm & length of 12 mm, T.B.R (Connect) and Branemark MKIII implant system were modeled with the diameter of 4 mm & length of 13 mm, Each model were simulated in the bone. Vertical force of 200 N and horizontal force of 100 N and resultant of the force exerted to lingual abutment. The amount of vertical & horizontal stress and shear stresses and maximum shear stresses and equivalent stresses were measured.Results: Under horizontal and inclined (lateral) loading the microthread systems showed less stress in comparison with microthread less systems in buccal and lingual cases. More over Branemark system showed less stress in lingual level and highest stress in buccal level. Under loading of vertical forces the microthread and microthread less systems showed different behaviors. T.B.R system showed less stress and Superline showed highest stress and Branemark placed in the third level after implantium.Conclusion: The findings in this research showed considerably the effect of microthreads in the stress distribution in the bone under different loading. It means that the dentist can control the quality & quantity of stress distribution in bone through selecting special implant design.

In this paper, a high-order finite element discretization and its newly developed fictitious domain approach, the finite cell method, are employed to compute a series of benchmark problems in the finite strain von Mises or J2 theory of plasticity. The hierarchical (integrated Legendre) shape functions are used for the finite element approximation of incompressible plastic dominated deformations occurring in the finite strain plasticity of ductile metals. The computational examples include the necking under uniaxial tension with notched and un-notched samples and the compression of a perforated plate. These computations demonstrate that the high-order finite element methods can provide a locking-free behavior with a pure displacement-based formulation. They also provide high convergence rates and robustness against high mesh distortions. In addition, it is shown that the finite cell method, on the top of the aforementioned advantages, provides easy mesh generation capabilities for highly complex geometries. The computational results are verified in comparison with the results obtained using a standard low-order finite element method known as the F-bar method. The numerical investigations reveal that both methods are good candidates for the plasticity analysis of engineering materials and structures made up of ductile materials, particularly those involving complex geometries.