Documents published in Scipedia

• Design parameters of dental implants: A review

  P. Rahmanivahid, M. Heidari

  Rev. int. métodos numér. cálc. diseño ing. (2022). Vol. 38, (1), 6

  
  

  Abstract

  An ideal dental implant is a design that maximizes the anchorage strength of implants in human jawbones and minimizes peak stress values in bone-implant interfaces under given standard loads. The stress concentration at the bone-implant contact is controlled by implant design, which determines the bone biological response. Implant design has improved as a result of marketing demands. The modification of shape, size, material, and surface topography of primary designs has been the focus of dental implant design in response to marketing needs. Since the integration of bone-implant has been highlighted in dentistry investigations, improving implant design depends on the prediction of mechanical reactions and remodeling response of bony tissues around implants. There are four types of implants design including Screws, cylinders, Conical cylinders, and Blades type implants. The major difference between these designs is in implant primary stability. With the development of computational technologies, researchers can predict long term oral bone remodeling around implants by use of the finite element method. This review considers the design parameters of dental implants in which affect stress, strain in bone-implant interfaces, and bone remodeling around the implant.

  Abstract
  An ideal dental implant is a design that maximizes the anchorage strength of implants in human jawbones and minimizes peak stress values in bone-implant interfaces under given [...]

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• Design and fabrication of a drill guide template for total elbow arthroplasty

  M. Heidari, P. Rahmanivahid, F. Yusof, J. Kashani

  Rev. int. métodos numér. cálc. diseño ing. (2021). Vol. 37, (1), 5

  
  

  Abstract

  Optimum implant positioning and technique used for its alignment are vital parameters to improve clinical results. Visual cues and jigs are utilized in the recent surgical techniques, which lead to some errors in the flexion-extension axis identification. Surgeons have used computer-assisted surgery for the alignment of the hip, knee, and shoulder. However, there is a restricted application of this technology to the elbow. In this study, a technique was used to model a drill guide template to precisely place an implant in the bone. The computed tomography dataset was used to construct four different elbow bones, and an elbow implant was modeled. The surgical drill guides were designed based on the computed tomography data. The drill guide templates and constructed bones were fabricated, using a 3D printer. The accuracy of the surgical guides was validated experimentally. The results showed that the mean deviations between the achieved and planned positions of the hole at the bone apex and base of bones were less than those reported in previous studies in both medial/lateral and posterior/anterior positions. The low positioning errors observed in this study proposed that the implant’s location can be precisely aligned to its target using the introduced technique.

  Abstract
  Optimum implant positioning and technique used for its alignment are vital parameters to improve clinical results. Visual cues and jigs are utilized in the recent surgical [...]

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• Effect of elbow implant design parameters on loosening: A finite element analysis

  M. Heidari, P. Rahmanivahid, S. Sharifi, M. Hashemi, E. Mohammadian, A. Akbari, Z. Razaviyan

  Rev. int. métodos numér. cálc. diseño ing. (2020). Vol. 36, (1), 20

  
  

  Abstract

  Loosening of an implant is the main complication after total elbow arthroplasty. The design parameters of the implant are a factor that contributes to the loosening of the implant. In this study, the correlation of loosening and geometry of the elbow implant component was investigated using the finite element method. Image processing software was used to construct elbow bones. Humeral and ulnar components were modeled with various cross-sections and flanges using modeling computer-aided design software. Modeling of all stems was based on conventional cemented fixation. Axial torsion and Anterior-posterior force were applied to the articular surface. Zero-displacement was applied to the proximal humerus and distal ulna. Bone graft was used between the flange and distal humerus bone. The stress shielding of bones and micro-motion were obtained in cement-implant-bone interfaces. Results showed that humeral and ulnar stems with modified diamond cross-section observed less micro-motion in the cement-bone-implant interfaces and as well as the least stress shielding in the distal humerus and proximal ulna compared to others. Furthermore, the modified flange, concave, transferred the least micro-motion to the bone-cement-implant interface and less stress shielding in distal humerus in comparison with trapezium and rectangular ones. This computational analysis represented a step in quantifying the role of interface micro-motion stress shielding of bone in initiating elbow implant loosening. A reduction of micro-motion and stress shielding through design modifications may improve the clinical outcomes.

  Abstract
  Loosening of an implant is the main complication after total elbow arthroplasty. The design parameters of the implant are a factor that contributes to the loosening of the [...]

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• Numerical analysis of side hull configuration in Trimaran

  M. Heidari, Z. Razaviyan, F. Yusof, E. Mohammadian, A. Alias, M. Akhbari, A. Akbari, F. Movahedi

  Rev. int. métodos numér. cálc. diseño ing. (2019). Vol. 35, (2), 32

  
  

  Abstract

  A trimaran is a multihull vessel designed to reduce wave-making resistances at high speeds. Optimization of the hull shape increases hull efficiency and speed of a vessel. The behavior of a ship is generally analyzed through numerical methods to save time and reduce high expenditures as compared to experimental methods. Although wide ranges of studies have investigated the hydrodynamic behavior of a vessel, the effect of trim angle, yaw angle, and heel angle of side hulls on hydrodynamic behavior of a trimaran has not been addressed properly. In the present study, a trimaran was modeled using computer-aided design software. Dimensions of the computational domain and boundary conditions were applied. Furthermore, mesh convergence was carried out. The accuracy of the method was validated. Analyses are based on the finite volume method. The analysis is carried out to obtain the resistance of side hulls and its effect on total trimaran resistance, effect of speed on hulls vessel resistance, wave patterns generated by the vessel at different trim and yaw angles, effect of trim, heel and yaw angles on side hull and total resistance of trimaran, the wetted surface at different trim, yaw, and heel angles, shape of free surface between the hulls, and the optimal position and trim angle of side hulls relative to the main hull. This computational analysis represents a step in quantifying the role of the trim, heel and yaw angles of side hulls on hydrodynamic characteristics of trimaran in calm water. The worth of information from present study may express the importance of the factors that could reduce the total resistance of a trimaran.

  Abstract
  A trimaran is a multihull vessel designed to reduce wave-making resistances at high speeds. Optimization of the hull shape increases hull efficiency and speed of a vessel. [...]

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