Zohreh Arabshahi

Manufacturing of flexible surgical guide for fully edentulous patients

Despite efficiency of modern implantology, unplanned perforation and drill deviation could be happened during freehand placement. The aim of this study was to provide a methodology for fabricating dental surgical drill guide for fully edentulous patients while it was flexible in term of changing drill diameter. The data of patient consisted of bone anatomy and radio-opaque template obtained from computed tomography. Jawbone and radio-opaque template three dimensional models converted into a three dimensional modeling software by means of an image processing package. Based on jawbone anatomy and radio-opaque template, implantation plan and design of surgical guides were carried out in three dimensional software. Rapid prototyping technique was used to manufacture several surgical guides to be used in different drilling sequences. Finally stainless steel tubes were accommodated passage of drill. Sequential surgical guides were different only in terms of the metal tubes internal diameter. This provides the ability of changing diameter of the implant or drill after fabricating surgical guide.

Influence of the TMJ Implant Geometry on Stress Distribution

The purpose of this study was to investigate the influence of Temporomandibular Joint implant geometry on stress distribution in total reconstruction of temporomandibular joint. A three dimensional model of a lower jaw of a patient was developed from a Computed Tomography scan images. Anatomical curvature and flat contact surface of implant design and fixation screws were modeled. Two implanted mandibles were then compared by means of finite element analysis. The muscle forces for incisal clenching were applied. The equivalent stress resulted in contact surface region of the bone and implant and in fixation screw holes were investigated to evaluate the designs. In applied loading condition, The results showed that anatomical design of implant was more preferred and it will lead to long-term success of implant.

Design Analysis of TMJ Implant under Physiological Loading Condition

Equal channel angular extrusion (ECAE) is a severe plastic deformation (SPD) method for obtaining bulk nanostructured materials. The ECAE die consists of two equal channels that intersect at an angle, usually between 90。and 135。. In the present study, the plastic deformation behavior of copper during the ECAE process with 120o die was investigated. To analyze the deformation behavior and the related strain distributions in the specimen, the commercial FE code ABAQUS has been used. The properties of the materials are strongly dependent on the shear plastic deformation behavior during equal channel angular extrusion (ECAE), which is controlled mainly by die geometry, material properties, and the friction between billet and the die. The ECAE process for these conditions was explained using the two different friction conditions of 0.15 and 0.08 to all sliding surfaces. The effective strain by the theoretical equation is in good agreement with the FEM results.

Finite element analysis of different ferrule heights of endodontically treated tooth

Objective: To investigate the influence of ferrule height on the crown mechanical resistance and stress distribution through the root and luting cement to explain restoration lose and root fracture pattern. Material and methods: Threedimensional models of an adult maxilla and root of incisor tooth were developed from a Computed Tomography scan images. Periodontal ligament, luting cement, crown and custom post were reconstructed on the computer . A static load of 50N was applied to the crown at 70° to the occlusal plan. Results: Design with no ferrule had the most crown displacement and 2mm ferrule had the least. Also 2mm ferrule design had the lowest root and luting cement stress Conclusion: The study suggests that a ferrule increases mechanical resistance of crown. Furthermore, a ferrule decreases stress in dentin and luting cement; consequently, the fracture and losing restoration risk decline.