The effect of different types of half pins on stress transfer parameter during osseointegration

Abstract Introduction: Pedicle screw fixation systems are widely used for treatment of various spinal pathologies, including spinal stenosis, scoliosis, spinal deformities and fractures. Stress shielding is considered to be a major factor contributing to insufficient fixation strength, leading to screw loosening. In this study, the influence of pedicle screw thread width on the displacement of pedicle screw and stress transfer is analyzed using 2-Dimensional axisymmetric finite element (FE) model. Methods: FE model consisting of cancellous and cortical bone, along with pedicle screw is developed for this study. The pedicle screw thread width is varied between 0.1 mm and 0.6 mm in steps of 0.1 mm, while the other geometric parameters, including screw half-angle, pitch, diameter, and length are kept constant. Three different contact conditions between screw and bone, such as frictionless, frictional, and bonded are considered to simulate hours, days, and months after surgery, respectively. The material properties and boundary conditions are applied based on previous studies. An axial force of 80 N is applied on the screw head to simulate axial pull-out test. Results: Similar patterns of stress distribution are observed for all screw models, with high stress concentration above the first thread. The highest displacement in screw is observed shortly after surgery, while the highest displacement in cancellous and cortical bone is observed few days and months after the surgery, respectively. The average von Mises stress in screw decreases with increase in thread width for all contact conditions. In few hours/days after the surgery, stress transfer parameter increases with increase in thread width, up to a thread width of 0.5 mm and then decreases. The changes in stress transfer parameter are negligible few months after the surgery. Conclusion: This study highlights the influence of thread width on displacement and stress transferred to the bone, at different durations after the surgery. It is observed that a thread width of 0.5 mm exhibits the highest stress transfer, leading to reduced stress shielding and improved bone remodeling. It appears that this study might aid in developing better pedicle screws for the treatment of various spinal pathologies.

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Comparison of stress transmission between implant-supported overdenture and removable partial denture prostheses in the edentulous mandible

10.21203/rs.2.12325/v1 ◽

2019 ◽

Author(s):

Gulsum Sayin Ozel ◽

Ozgur Inan ◽

Ozgun Yusuf Ozyilmaz

Keyword(s):

Stress Distribution ◽

Stress Transfer ◽

Titanium Implants ◽

Ease Of Use ◽

Force Transmission ◽

Removable Partial Denture ◽

Alternative Treatment Option ◽

Edentulous Mandible ◽

Different Types ◽

Stress Transmission

Abstract Background: A new treatment concept using two or four implant-supported fixed prosthesis-retained removable partial dentures has been proposed for an edentulous mandible. However, the stress transmission of this new system is unknown. The purpose of this study was to compare the stress transfer characteristics of two different types of implant-supported prostheses (implant-supported overdentures and implant-supported removable partial dentures) retained by two or four implants via photoelastic stress analysis. Methods: This study was designed to evaluate the force transmission of commercially available titanium implants inserted into edentulous mandibles composed of photoelastic resin within two to four implants using two different types of prosthesis: overdentures and implant-retained removable partial dentures. In all models, implants were placed parallel to each other and the midline. A 300 N load was applied first to the premolars. Loading and stress distributions were photographed after the completion of the prostheses. Results: In the models with two implant-retained removable partial dentures, the stress distribution was found to be lower than that with the four implant-retained removable partial dentures. The locator, a stud attachment, showed the most equitable stress distribution for overdenture models. Despite this, non-splinted implants caused high stresses around the distal implant on the loading side. Conclusions: When models were compared, the stress loads were transmitted to other implants by splinting. Acceptable stresses were observed in implant-supported removable dentures, especially those with precision attachments. Implant-supported removable partial dentures with an anterior fixed prosthetic design may serve as an acceptable and affordable alternative treatment option. These dentures appear to be advantageous in terms of stress transmission considering effects such as ease of use, esthetic requirements, patient requests, and reduction in the area covered by the prosthesis.

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Effect of the Presence of Mortar Joints in the Bond Behaviour of Tuff Masonry Elements

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.624.526 ◽

2014 ◽

Vol 624 ◽

pp. 526-533 ◽

Cited By ~ 6

Author(s):

Francesca Ceroni ◽

Angelo Garofano ◽

Marisa Pecce ◽

Gian Marco Procaccini

Keyword(s):

Southern Italy ◽

Base Material ◽

Stress Transfer ◽

Local Stress ◽

Bond Behaviour ◽

Lap Shear ◽

Experimental Campaign ◽

Different Types ◽

Glass Carbon ◽

Set Up

In this paper, the bond behaviour of masonry elements made of tuff stone and bonded with different types of FRP fabrics (glass, carbon, basalt) has been investigated through an experimental campaign. Tuff is a natural stone representing a very common base material for the construction of masonry buildings in Southern Italy and many Mediterranean areas. Two series of specimens have been tested: 1) single blocks and 2) prisms made of three blocks and two mortar joints. The tests have been carried out according to a single-lap shear scheme according to a push-pull set-up. Presence of a plastering was also investigated for both series. The experimental results have been examined in terms of both debonding load and local stress transfer phenomena in order to evidence the performance of the different fibres and the effect of both mortar joints and plastering.

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Modeling of the Interfacial Stress Transfer Parameter for Polymer/Carbon Nanotube Nanocomposites

Physical Mesomechanics ◽

10.1134/s102995992006017x ◽

2020 ◽

Vol 23 (6) ◽

pp. 616-620

Author(s):

Y. Zare ◽

K.-Y. Rhee

Keyword(s):

Carbon Nanotube ◽

Stress Transfer ◽

Interfacial Stress ◽

Transfer Parameter

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The extinction time of a general birth and death process with catastrophes

Journal of Applied Probability ◽

10.1017/s0021900200116031 ◽

1986 ◽

Vol 23 (04) ◽

pp. 851-858 ◽

Cited By ~ 1

Author(s):

P. J. Brockwell

Keyword(s):

Laplace Transform ◽

Size Distribution ◽

Sufficient Conditions ◽

Necessary And Sufficient Conditions ◽

Death Process ◽

Extinction Time ◽

Birth And Death Process ◽

Different Types ◽

The Laplace Transform ◽

Necessary And Sufficient

The Laplace transform of the extinction time is determined for a general birth and death process with arbitrary catastrophe rate and catastrophe size distribution. It is assumed only that the birth rates satisfyλ0= 0,λj> 0 for eachj> 0, and. Necessary and sufficient conditions for certain extinction of the population are derived. The results are applied to the linear birth and death process (λj=jλ, µj=jμ) with catastrophes of several different types.

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Differentiating between different forms of moral obligations

Behavioral and Brain Sciences ◽

10.1017/s0140525x19002589 ◽

2020 ◽

Vol 43 ◽

Author(s):

Rajen A. Anderson ◽

Benjamin C. Ruisch ◽

David A. Pizarro

Keyword(s):

Moral Character ◽

Moral Obligations ◽

Different Types

Abstract We argue that Tomasello's account overlooks important psychological distinctions between how humans judge different types of moral obligations, such as prescriptive obligations (i.e., what one should do) and proscriptive obligations (i.e., what one should not do). Specifically, evaluating these different types of obligations rests on different psychological inputs and has distinct downstream consequences for judgments of moral character.

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Ultrastructural Investigations of the Contractile Filaments of Amoebae

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100050950 ◽

1974 ◽

Vol 32 ◽

pp. 188-189

Author(s):

P.L. Moore

Keyword(s):

Cytoplasmic Streaming ◽

Three Dimensional ◽

Freeze Fracture ◽

Amoeboid Movement ◽

Different Types ◽

Chemical Conditions ◽

Complete Interpretation

Previous freeze fracture results on the intact giant, amoeba Chaos carolinensis indicated the presence of a fibrillar arrangement of filaments within the cytoplasm. A complete interpretation of the three dimensional ultrastructure of these structures, and their possible role in amoeboid movement was not possible, since comparable results could not be obtained with conventional fixation of intact amoebae. Progress in interpreting the freeze fracture images of amoebae required a more thorough understanding of the different types of filaments present in amoebae, and of the ways in which they could be organized while remaining functional.The recent development of a calcium sensitive, demembranated, amoeboid model of Chaos carolinensis has made it possible to achieve a better understanding of such functional arrangements of amoeboid filaments. In these models the motility of demembranated cytoplasm can be controlled in vitro, and the chemical conditions necessary for contractility, and cytoplasmic streaming can be investigated. It is clear from these studies that “fibrils” exist in amoeboid models, and that they are capable of contracting along their length under conditions similar to those which cause contraction in vertebrate muscles.

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Study of the Molecular Architecture of Keratin Filaments by Electron Microscopy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100053310 ◽

1982 ◽

Vol 40 ◽

pp. 118-119

Author(s):

U. Aebi ◽

P. Rew ◽

T.-T. Sun

Keyword(s):

Electron Microscopy ◽

Structural Organization ◽

Cell Types ◽

Structural Features ◽

Molecular Architecture ◽

The Past ◽

Keratin Filaments ◽

Different Types ◽

10 Nm Filaments ◽

Different Cell Types

Various types of intermediate-sized (10-nm) filaments have been found and described in many different cell types during the past few years. Despite the differences in the chemical composition among the different types of filaments, they all yield common structural features: they are usually up to several microns long and have a diameter of 7 to 10 nm; there is evidence that they are made of several 2 to 3.5 nm wide protofilaments which are helically wound around each other; the secondary structure of the polypeptides constituting the filaments is rich in ∞-helix. However a detailed description of their structural organization is lacking to date.

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A New Defect in Polyethylene Single Crystals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100070795 ◽

1973 ◽

Vol 31 ◽

pp. 70-71

Author(s):

E. L. Thomas ◽

S. L. Sass

Keyword(s):

Single Crystals ◽

Screw Dislocation ◽

Small Distance ◽

Dipole Model ◽

Dislocation Dipole ◽

Chain Folding ◽

Black And White ◽

Polymer Crystal ◽

Different Types

In polyethylene single crystals pairs of black and white lines spaced 700-3,000Å apart, parallel to the [100] and [010] directions, have been identified as microsector boundaries. A microsector is formed when the plane of chain folding changes over a small distance within a polymer crystal. In order for the different types of folds to accommodate at the boundary between the 2 fold domains, a staggering along the chain direction and a rotation of the chains in the plane of the boundary occurs. The black-white contrast from a microsector boundary can be explained in terms of these chain rotations. We demonstrate that microsectors can terminate within the crystal and interpret the observed terminal strain contrast in terms of a screw dislocation dipole model.

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