Background and aim: Dental irreversible hydrocolloid (Alginate) is a major dental used world wide in many clinical procedures. The purpose of this study was to investingate the dimensional stability after prolonged storage of Alginate Elastic Chromo. This study was carried out in 2008 in Azad Islamic university.Method and Material: This experimental study was carried out by using labratory metal master model that contained two dies.20 impression were taken for master model by Alginate Elastic Chromo The four storage conditions were as follow: 0/5 hours, 24 hours , 48 hours, 120 hours, stone model were poured. Die's height, diameter and distance between dies were measured by profile projector and compared with labratory model by use ANOVA test.Results: There is no significant different between of four times casting. Height & distance dimensional change were less than 1/5% (Max distoration after 24 hours) but diameters were more than 1/5%.Conclusion: Alginate Elastic Chromo was not dimensionally stable over a 5 day period ( 120 hours). However, no effect of the times on dimensional change.

Objective: To investigate the effect of Romberg Exercise on balance improvement in elderly persons, 70 elderly persons with the history of two or more falling during recent 3 months were selected from Kahrizak nursing home in Tehran (38 as cases and 32 as controls).Materials & Methods: Romberg Exercise was done in case group every day (45 minute per day and one time each day) for 3 months. Among all persons, 28 persons in case group and 21 persons in control group were followed for 6 months and incidence and frequency of falling were assessed during this time.Results: The Incidence of one or more falling in case and control groups was 31.3% and 47.6% in men and 57.9% and 27.3% in women, respectively. We found no significant relation between gender and the incidence of falling (P=0.460). Also, no significant relation was found between age and incidence (P=0.554) and frequency of falling (P=0.144) in elderly persons.Conclusion: Although the effect of Romberg Exercise on improvement of balance disturbance and falling was not demonstrated, it needs additional studies with larger sample size and longer follow-up.

In this paper, a corotational Lagrangian finite element method is presented to analyze the geometric and material nonlinearity problems using degenerated shell and solid elements. The formulation is based on the updated - Lagrangian conjugate stress and strain tensors with the linear and nonlinear terms to eliminate the approximation of the Cauchy stress in the finite element formulation. Linear work hardening and Prandtle-Reuss flow rule along with 1`von-Mises yield criterion is used to model material nonlinearity. To investigate the accuracy and computational efficiency of the formulation, some examples in Elastic and Elastic-plastic regime is presented. Also, the results obtained from this method are compared with those available using other corotaional finite element formulations.

Determining the mechanical characteristics of the artery is very essential for the production of vascular implants. In the present work, the mechanical characteristics of arterial walls were investigated by considering plaque and stent in a 3D model. This article aims to investigate the effect of the arterial tissue with the same boundary conditions and restrictions for an artery blocked with the plaque and stent, in creating stress in the tissue. An intravascular stent implantation is a treatment method whose success largely depends on the mechanical characteristics of each vascular component, plaque and stent, and blood flow pressure. For opening up the blood flow in the blocked artery, stents could be used as medical devices. In this research, a stent was designed, and its impact on all three models of Elastic, viscoElastic, and hyper-Elastic arterial tissue with plaque was studied and compared. An ideal finite element model was made to find the effect of three types of the artery tissue (Elastic, viscoElastic, hyper-Elastic) with the systolic and diastolic blood flow pressure to observe the stress and the deformation of arteries, plaques, and stents. In addition, for the hyper-Elastic model, two Mooney-Rivlin and Ogden models were also investigated. It was found that the type of artery had an effective impact on the result of the stress and the deformation created in the stented artery. Moreover, the results illustrated that considering different models for the artery tissue affected the plaque and stent behavior. Arteries exhibit interesting mechanical behaviors. In the present study, an attempt was made to investigate different mechanical behaviors of arteries with the plaque and stent obstruction. In the examined models, the stress for the artery and plaque was higher in the Ogden model and the lowest one was in the viscoElastic model, and the deformation was higher in the viscoElastic model and lower in the Ogden model. It should be noted that the average stress for the vessel in the Ogden model was about 50% higher than the viscoElastic model. Pathological changes in the walls of the vessels can lead to high-risk cardiovascular diseases such as heart attacks and strokes. Understanding arterial mechanical behaviors provides valuable insight into disease. Therefore, the investigation of different behavioral models helps to evaluate the behavior of the arterial wall by considering the composition and function of the tissue.