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.

Background and Aim: Over the last few years, concept of platform switching has gained popularity for reducing degree of crestal bone resorption. Many researchers believe that, this theory can be used for improving stress distribution in implant-bone interface. The purpose of this three dimensional FINITE ELEMENT Analysis (FEA) was to study and compare stress distribution in implant-bone interface and implant-abutment interface of 3i implants (Biomet 3i, USA) in mandibular molar area.Materials & Methods: For this FEA, computed tomography (CT) images of an adult human mandible was used to make the three-dimensional model of posterior edentulous mandible. The implant systems which used was the 3i system consisted of 3i fixtures: 4 and 5 mm in diameter and 11.5 mm in length, and 3i Certain abutment 4.1 and 5mm (Biomet 3i, USA). This implant systems were assembled on the mandible model in 3 different designs: a platform-switched configuration; MODEL 4: 4-mm 3i fixture, 4.1-mm abutment; MODEL 5: 5-mm 3i fixture, 5-mm abutment; MODEL 6: 5-mm 3i fixture, 4.1-mm abutment, a platform-switched configuration. A linear static analysis was performed on the prepared 3D solid models with two different oblique load of 100 and 250 N in the lingobuccal direction with 15 degrees of inclination on the center of the abutment.Results: Regardless of the implant system used, maximum Von Mises stresses in cortical bone around implants were lower in platform switched models compared to matching diameter implant-abutment. This effect was not related to the usage of larger implant diameters in these models. However, Von Mises stresses in implant-abutment interface were the lowest in models with larger implant diameter. Conclusion: The platform switching technique reduces the stress concentration in the area of crestal bone-implant interface and shifted it to the area of implant-abutment interface. In the present study, this stress reduction was not.

one of the simplest numerical integration method which provides a large saving in computational efforts, is the well known one-point Gauss quadrature which is widely used for 4 nodes quadrilateral ELEMENTs. On the other hand, the biggest disadvantage to one-point integration is the need to control the zero energy modes, called hourglassing modes, which arise. The efficiency of four different anti-hourglassing approaches, Flanagan (elastic approach), Dyna3d, Hansbo and Liu have been investigated. The first two approaches have been used in 2 and 3-D explicit codes and the latter have been employed in 2-D implicit codes. For 2-D explicit codes, the computational time was reduced by 55% and 60% for elastic and Dyna3d, respectively. However, for 3-D codes the reduction was dependent on the number of ELEMENTs and was obtained between 50% and 70%. Also, the error due to the application of elastic methods was less than that for Dyna3d when the results were compared with those obtained from 2-points Gauss quadrature. Nevertheless, the convergence occurred more rapidly and the oscillations were damped out more quickly for Dyna3d approach. For implicit codes, the anti-hourglassing methods had no effect on the computations and therefore a 2-points Gauss quadrature is recommended for implicit codes as it provide the results more accurately

Aim: The aim of this investigation was to reveal the biomechanical changes of mandible during chin cup therapy using the FINITE ELEMENT method.Material and Method: A three dimensional ELEMENTed model of mandible was reconstructed from a young human skull by means of a well developed software. The mandible was supposed to be fixed at the superior surface of glenoid fossa of the computerized model to determine the boundary of forces applied by chin cup. Two forces of 400 and 900 grams were applied to the pogonion of the mandible in relation to the line connecting pogonion to the condyle. Stress distribution was analysed from the loads and direction of displacement of mandible.Results: Compressive stress was clearly present in pogonion and anterior border of ramus, particularly in the junction with the body of mandible. The distribution of stress was also present in the whole body of the mandible, ramus and surface of condyle, although it was greater in anterior portion of the condyle and it's neck. Tensile stress was present in the inferior border of the body of mandible and posterior border of the ramus, specially near the condyle neck.Conclusion: The mandibular displacement was determined to be at upward and backward directions.

Wavelet Analysis has called the attentions in numerical solutions of PDEs in recent years. Because of orthogonality and compact support of Daubechies scaling functions, these functions have excellent ability of providing good accuracy and convergence for the approximation of the solution in singularities. In this article the method of using these functions for numerical solving of PDE for Euler–Bernoulli beams is formulated. This procedure needs to calculate derivatives and integrals of scaling functions as the shape functions of wavelet-based FINITE ELEMENT method. Because of non-explicit formulation and high oscillation of these functions, conventional methods -like Gauss method for integration- are not suitable and accurate. Thus some special methods are formulated for these requirements. The ability and high accuracy of wavelet-based beam ELEMENT for different boundary conditions and loads is shown in some examples.