Analysis of the Pullout Testing of Straight and Angled Abutments in Narrow Diameter Implants

2020 ◽  
Vol 1012 ◽  
pp. 461-465
Author(s):  
Ana Lígia Piza Micelli ◽  
Frederico Nigro ◽  
Cristiano Stefano Mucsi ◽  
Maicon Cavalieri ◽  
Luís Cláudio Aranha ◽  
...  
Keyword(s):  
Statistical Difference ◽  
Mechanical Stability ◽  
Screw Loosening ◽  
Pullout Resistance ◽  
Osseointegrated Implants ◽  
Fixation Screw ◽  
Pullout Testing ◽  
Pullout Load ◽  
Common Problems ◽  
Narrow Diameter Implants

Despite the success of osseointegrated implants, some biomechanical problems such as loosening or fracture of the abutment, crown fixation screw loosening and prosthetic instability, are common problems reported in the literature. Thus, the objective of the present study was to analyze the pullout resistance of straight and angled abutments in narrow diameter implants installed by means of friction. The specimen was composed of an implant of 3.3 mm x 11 mm fixed 2 mm above of a resin block. The abutments were fixed by friction receiving 3, 5 and 7 strikes of 0.05 J along the implant axis, and were positioned with 0 ̊, 10 ̊ and 20 ̊ of angulation. The abutments were subjected to pullout load, totalizing 10 repetitions for each test, i.e., the abutment was reinserted up to 10 times in the same implant. The results showed higher values of pullout load for the abutments with 7 strikes, and no statistical difference with 5 strikes suggesting better mechanical stability.

Load-strain-displacement response of geosynthetics in monotonic and cyclic pullout

1998 ◽  
Vol 35 (2) ◽  
pp. 183-193 ◽  
Author(s):  
D M Raju ◽  
R J Fannin
Keyword(s):  
Relative Displacement ◽  
Cyclic Loads ◽  
Normal Stresses ◽  
Constant Ratio ◽  
Pullout Resistance ◽  
Maximum Resistance ◽  
Constant Rate ◽  
Pullout Testing ◽  
Pullout Behaviour ◽  
Cyclic Dynamic

Mobilization of the pullout resistance of geosynthetics in monotonic and cyclic modes is described from both displacement- and load-controlled tests performed at normal stresses in the range 4-17 kPa. The tests were performed on three geogrids and two geomembranes embedded nearly 1.0 m in a uniformly graded sand. Results for load-controlled tests at a constant rate of 0.25 kN/(m ·min-1), followed by several series of load cycles of increasing amplitude, are compared with displacement-controlled tests at a constant rate of 0.5 mm/min. In general the geogrids behave as an equivalent textured sheet. Pullout behaviour, and especially the incremental displacement mobilized at cyclic loads close to the maximum resistance, is found to vary with type of geogrid. In only one case was cyclic pullout resistance of a grid found to exceed the monotonic resistance. A comparison of the cyclic and monotonic response yields a constant ratio of pullout resistance at large displacement, but one which is not unique to a particular specimen. Cyclic strains of decreasing amplitude are mobilized along a test specimen, with most of the necessary relative displacement occurring close to the loaded end and the embedded end showing little response.Key words: pullout testing, monotonic, cyclic, dynamic, geosynthetics, reinforced walls.

scholarly journals Effective Length Prediction and Pullout Design of Geosynthetic Strips Based on Pullout Resistance

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6151
Author(s):  
Jeongjun Park ◽  
Gigwon Hong
Keyword(s):  
Effective Area ◽  
Soil Reinforcement ◽  
Effective Length ◽  
Block Type ◽  
Front Wall ◽  
Test Results ◽  
Pullout Strength ◽  
Area Method ◽  
Pullout Resistance ◽  
Pullout Load

In this study, pullout tests were conducted on geosynthetic strips which can be applied to a block-type front wall. Based on the test results, the effective length is predicted, and the pullout design results are presented. In other words, the pullout displacement–pullout load relationship of all geosynthetic strips was analyzed using the pullout test results, and their effective lengths were predicted. It was found that the reinforcement width affected the pullout force for the geosynthetic strips at the same tensile strength. The pullout behavior was evidenced within a range of approximately 0.45 L of the total length of the reinforcement (L) and hardly occurred beyond a certain distance from the geosynthetic strips front regardless of the normal stress. Based on these pullout behavioral characteristics, a method is proposed for the prediction of the effective length (LE) and maximum effective length (LE(max)) of a geosynthetic strip. The pullout strength was compared using the total area and effective area methods in accordance with the proposed method. In the case of the total area method, GS50W (width: 50 mm) and GS70W (width: 70 mm) exhibited similar pullout strengths. The pullout strength by the effective area method, however, was found to be affected by the soil-reinforcement interface adhesion. The proposed method used for the prediction of the effective length of a geosynthetic strip was evaluated using a design case. It was confirmed that the method achieved an economical design in instances in which the pullout resistance by the effective length (LE) was applied compared with the existing method.

Laboratory Experimental Study on Pullout Behavior of Mortar Grouted GFRP Soil Nails

2010 ◽  
Vol 168-170 ◽  
pp. 1069-1072
Author(s):  
Zhong Yu Liu ◽  
Chong Wu Ma ◽  
Zhuo Zhao
Keyword(s):  
Large Scale ◽  
Axial Strain ◽  
Hyperbolic Function ◽  
Overburden Pressure ◽  
Soil Nails ◽  
Pullout Resistance ◽  
Pull Out ◽  
Glass Fiber Reinforced ◽  
Dilatancy Effect ◽  
Pullout Load

A large-scale laboratory apparatus has been built to study the pullout behavior of mortar grouted glass fiber reinforced polymer (GFRP) soil nails. The axial strain along the nail length and the displacement of the nail head under different pullout loads are measured, and the ultimate pullout load under the overburden pressure is obtained. Then, the influence of the overburden pressure on the ultimate value of the interface friction force is investigated. The experimental results illustrate that the pullout behavior of mortar grouted GFRP soil nails is similar to that of mortar grouted steel soil nails, and the relation between the displacement and the pullout load can be described with the hyperbolic function. In addition, the dilatancy effect of the soil near the nail during pull out should be taken into account in estimating the pullout resistance of soil nails in dense fills.

Response of buried steel pipelines subjected to relative axial soil movement

2009 ◽  
Vol 46 (7) ◽  
pp. 735-752 ◽  
Author(s):  
Dharma Wijewickreme ◽  
Hamid Karimian ◽  
Douglas Honegger
Keyword(s):  
Earth Pressure ◽  
Axial Direction ◽  
Full Scale ◽  
Interface Shear ◽  
Dense Sand ◽  
Pullout Resistance ◽  
Soil Movement ◽  
Pullout Testing ◽  
Research Findings ◽  
Dry Sand

The performance of buried steel pipelines subjected to relative soil movements in the axial direction was investigated using full-scale pullout testing in a soil chamber. Measured axial soil loads from pullout testing of pipes buried in loose dry sand were comparable to those predicted using guidelines commonly used in practice. The peak values of axial pullout resistance observed on pipes buried in dense dry sand were several-fold (in excess of 2 times) higher than the predictions from guidelines; the observed high axial pullout resistance is primarily due to a significant increase in normal soil stresses on the pipelines, resulting from constrained dilation of dense sand during interface shear deformations. This reasoning was confirmed by direct measurement of soil stresses on pipes during full-scale testing and numerical modeling. The research findings herein suggest that the use of the coefficient of lateral earth pressure at-rest (K0) to compute axial soil loads, employing equations recommended in common guidelines, should be undertaken with caution for pipes buried in soils that are likely to experience significant shear-induced dilation.

scholarly journals INFLUENCE OF DIAMETER AND GEOMETRY IN THE TAPPING OF THE PILOT HOLE IN PEDICLE SCREWS

2019 ◽  
Vol 18 (1) ◽  
pp. 51-54
Author(s):  
Helton Luiz Aparecido Defino ◽  
Raffaello de Freitas Miranda ◽  
Romulo Pedroza Pinheiro ◽  
Antonio Carlos Shimano
Keyword(s):  
Statistical Difference ◽  
Pedicle Screws ◽  
Insertion Torque ◽  
Significance Level ◽  
Pilot Hole ◽  
Pullout Resistance ◽  
Screw Diameter ◽  
Pulling Force ◽  
Different Diameters ◽  
Experimental Group

ABSTRACT Objective: To evaluate the insertion torque and the pulling force of each screw with different diameters and tap. Methods: Polyurethane blocks with a pilot hole of 2.7 mm were used in the study. An experimental group with 5 blocks was formed, the insertion torque was evaluated with a torque meter, and the pullout strength of each Globus screw of 5.5 mm and 6.5 mm was assessed. Results: The comparison of the insertion torque on the 5.5 mm screws with pilot hole without tapping and with a smaller diameter than that of the screw (4.5 mm) and a different thread, and with the tapping with the same diameter as that of the screw (5.5 mm) and equal or different thread presented a statistical difference with a higher value of the insertion torque in the group in which the tapping was not performed. As for the pulling force of the 5.5 mm screw, the non-tapping of the pilot hole resulted in statistical difference with the same diameter of the screw (5.5 mm) and with a different thread of the screw. The pullout force on the 6.5 mm screw was higher in the group where the pilot hole was not tapped according to the non-parametric Kruskal-Wallis test, with significance level of p <0.05 in the comparison of the groups. Conclusions: Pilot hole tapping reduced insertion torque and pullout resistance of the pedicle screw influencing the fixation with tapping with the same screw diameter and different thread design.

scholarly journals Integrating Finite Element Death Technique and Bone Remodeling Theory to Predict Screw Loosening Affected by Radiation Treatment after Mandibular Reconstruction Surgery

Diagnostics ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 844
Author(s):  
Le-Jung Wu ◽  
Kai-Hung Hsieh ◽  
Chun-Li Lin
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Bone Remodeling ◽  
Fe Simulation ◽  
Radiation Treatment ◽  
Fe Model ◽  
Screw Loosening ◽  
Predictive Diagnosis ◽  
Fixation Screw ◽  
Distal Fixation

This study developed a numerical simulation to understand bone mechanical behavior and micro-crack propagation around a fixation screw with severe mandibular defects. A mandible finite element (FE) model was constructed in a rabbit with a right unilateral body defect. The reconstruction implant was designed to be fixed using six screws distributed on the distal and mesial sides. The element death technique provided in FE analysis was combined with bone remodeling theory to simulate bone necrosis around the fixation screw in which the strain value reached the overload threshold. A total of 20 iterations were performed to observe the micro-crack propagation pattern for each screw according to the high strain locations occurring in each result from consecutive iterations. A parallel in vivo animal study was performed to validate the FE simulation by placing specific metal 3D printing reconstruction implants in rabbits to compare the differences in bone remodeling caused by radiation treatment after surgery. The results showed that strain values of the surrounding distal bone fixation screws were much larger than those at the mesial side. With the increase in the number of iteration analyses, the micro-crack prorogation trend for the distal fixation screws can be represented by the number and element death locations during the iteration analysis process. The corresponding micro-movement began to increase gradually and induced screw loosening after iteration calculation. The strained bone results showed that relatively high bone loss (damage) existed around the distal fixation screws under radiation treatment. This study concluded that the FE simulation developed in this study can provide a better predictive diagnosis method for understanding fixation screw loosening and advanced implant development before surgery.

scholarly journals Predicting implant stability: in vitro validation in artificial bone

2008 ◽  
Author(s):  
Thibaut Bardyn
Keyword(s):  
Finite Element ◽  
Mechanical Stability ◽  
A Priori ◽  
Primary Stability ◽  
Computer Assisted ◽  
Implant Stability ◽  
Element Analysis ◽  
Osseointegrated Implants ◽  
The Stability

Primary stability of osseointegrated implants is necessary for short and long-term success of the treatment. This paper presents a method to help clinicians preoperatively assess this primary implant stability. The method combines a planning software with a in-house finite element solver. Once the clinician has chosen a position for the implant on the planning tool, a finite element analysis is automatically started and calculates the mechanical stability of the implant at this position. The process is designed to be as simple and fast as possible for an efficient clinical use. Mechanical testing material was used to validate the stability measured by the software. The novel tool presented here leads the way to a new generation of intelligent computer-assisted tools able to give a priori indication on the life span of the implant.

An improved design for an Scanning Tunnelling Microscope (STM) for use in a Transmission Electron Microscope (TEM)

1991 ◽  
Vol 49 ◽  
pp. 384-385
Author(s):  
W.K. Lo ◽  
J.C.H. Spence
Keyword(s):  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Mechanical Stability ◽  
Scanning Tunnelling Microscope ◽  
Reflection Mode ◽  
Specimen Holder ◽  
Transmission Electron ◽  
Scanning Tunnelling ◽  
Improved Design

An improved design for a combination Scanning Tunnelling Microscope/TEM specimen holder is presented. It is based on earlier versions which have been used to test the usefulness of such a device. As with the earlier versions, this holder is meant to replace the standard double-tilt specimen holder of an unmodified Philips 400T TEM. It allows the sample to be imaged simultaneously by both the STM and the TEM when the TEM is operated in the reflection mode (see figure 1).The resolution of a STM is determined by its tip radii as well as its stability. This places strict limitations on the mechanical stability of the tip with respect to the sample. In this STM the piezoelectric tube scanner is rigidly mounted inside the endcap of the STM holder. The tip coarse approach to the sample (z-direction) is provided by an Inchworm which is located outside the TEM vacuum.

Experiments with a scanning tunneling microscope (STM) mounted in a scanning electron microscope (SEM)

1986 ◽  
Vol 44 ◽  
pp. 636-639
Author(s):  
Oliver C. Wells ◽  
Mark E. Welland
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Mechanical Stability ◽  
Tunneling Current ◽  
Feedback System ◽  
Scanning Tunneling ◽  
Surface Profiling ◽  
Close Proximity ◽  
Metal Tip ◽  
Scanning Electron

Scanning tunneling microscopes (STM) exist in two versions. In both of these, a pointed metal tip is scanned in close proximity to the specimen surface by means of three piezos. The distance of the tip from the sample is controlled by a feedback system to give a constant tunneling current between the tip and the sample. In the low-end STM, the system has a mechanical stability and a noise level to give a vertical resolution of between 0.1 nm and 1.0 nm. The atomic resolution STM can show individual atoms on the surface of the specimen.A low-end STM has been put into the specimen chamber of a scanning electron microscope (SEM). The first objective was to investigate technological problems such as surface profiling. The second objective was for exploratory studies. This second objective has already been achieved by showing that the STM can be used to study trapping sites in SiO2.

Electron microscopy of keratinocytes cultured on a collagen substrate used as an allograft for the treatment of chronic wounds

1992 ◽  
Vol 50 (2) ◽  
pp. 1104-1105
Author(s):  
Debby A. Jennings ◽  
Michael J. Morykwas ◽  
Louis C. Argenta
Keyword(s):  
Electron Microscopy ◽  
Cell Suspension ◽  
Single Cell ◽  
Chronic Wounds ◽  
Mechanical Stability ◽  
Uv Light ◽  
Type I ◽  
Single Cell Suspension ◽  
Collagen Substrate ◽  
Dermal Collagen

Grafts of cultured allogenic or autogenic keratlnocytes have proven to be an effective treatment of chronic wounds and burns. This study utilized a collagen substrate for keratinocyte and fibroblast attachment. The substrate provided mechanical stability and augmented graft manipulation onto the wound bed. Graft integrity was confirmed by light and transmission electron microscopy.Bovine Type I dermal collagen sheets (100 μm thick) were crosslinked with 254 nm UV light (13.5 Joules/cm2) to improve mechanical properties and reduce degradation. A single cell suspension of third passage neonatal foreskin fibroblasts were plated onto the collagen. Five days later, a single cell suspension of first passage neonatal foreskin keratinocytes were plated on the opposite side of the collagen. The grafts were cultured for one month.The grafts were fixed in phosphate buffered 4% formaldehyde/1% glutaraldehyde for 24 hours. Graft pieces were then washed in 0.13 M phosphate buffer, post-fixed in 1% osmium tetroxide, dehydrated, and embedded in Polybed 812.

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