Load Response of Periodontal Ligament: Assessment of Fluid Flow, Compressibility, and Effect of Pore Pressure

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
Marzio Bergomi ◽  
H. W. Anselm Wiskott ◽  
John Botsis ◽  
Aïssa Mellal ◽  
Urs C. Belser
Keyword(s):  
Pore Pressure ◽  
Periodontal Ligament ◽  
Mechanical Response ◽  
Poisson Ratio ◽  
Surrounding Medium ◽  
Pressure Chamber ◽  
Solid Matrix ◽  
Fluid Exchange ◽  
Load Response ◽  
Custom Made

The periodontal ligament (PDL) functions both in tension and in compression. The presence of an extensive vascular network inside the tissue suggests a significant contribution of the fluid phase to the mechanical response. This study examined the load response of bovine PDL under different pore pressure levels. A custom-made pressure chamber was constructed. Rod-shaped specimens comprising portions of dentine, bone, and intervening layer of PDL were extracted from bovine mandibular molars. The dentine ends of the specimens were secured to the actuator while the bone ends were affixed to the load cell. The entire assemblage was surrounded by the pressure chamber, which was then filled with saline. Specimens loaded at 1.0 Hz sinusoidal displacement were subjected to four different environmental fluid pressures (i.e., pressures of 0.0–1.0 MPa). The video images recorded during the tests were analyzed to determine whether or not fluid exchange between the PDL and the surrounding medium took place during mechanical loading. A value for the tissue’s apparent Poisson ratio was also determined. The following observations were made: (1) fluid was squeezed out and pumped into the ligament during the compressive and tensile loading phases, (2) the PDL was highly compressible, and (3) the pore pressure had no influence on the mechanical response of the PDL. The present tests emphasized the biphasic structure of PDL tissue, which should be considered as a porous solid matrix through which fluid can freely flow.

Biomechanical Analysis of a Custom-Made Mouthguard Reinforced With Different Elastic Modulus Laminates During a Simulated Maxillofacial Trauma

2020 ◽  
pp. 194338752098023
Author(s):  
João Paulo Mendes Tribst ◽  
Amanda Maria de Oliveira Dal Piva ◽  
Pietro Ausiello ◽  
Arianna De Benedictis ◽  
Marco Antonio Bottino ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Bone Tissue ◽  
Periodontal Ligament ◽  
Mechanical Response ◽  
Element Model ◽  
Biomechanical Analysis ◽  
Hard Material ◽  
Anterior Teeth ◽  
Custom Made ◽  
Root Dentin

Background/Aims: There is a lack of data regarding the influence of different laminates for mouthguard reinforcement in the mechanical response during an impact in the orofacial region. The aim of this study was to verify the influence of the laminate framework on the stresses and strains of the anterior teeth and displacement of ethylene-vinyl acetate (EVA) custom-made mouthguards during a simulated impact. The null hypotheses was that the different laminates reinforcement would present the similar effect in maxillary structures, regardless the elastic modulus. Methods: A finite element model of human maxillary central incisors with an antagonist contact was used. A linear quasi-static analysis was used to simulate the force exerted during an impact. A total of 5 different layers were simulated inside the mouthguard at the labial portion according to the Elastic Modulus 1 MPa (Extremely flexible), 9 GPa (Low modulus reinforcement), 18 GPa (Without reinforcement), 50 GPa (Flexible alloy), 100 GPa (Titanium alloy) and 200 GPa (Hard material). The results were evaluated by means of Maximum Principal Stress (in the tooth and bone), Microstrain (periodontal ligament) and Displacement (mouthguard) criteria. Results: The elastic modulus of the material inside the MG influenced the stress distribution on the enamel buccal face. However, it did not affect the bone tissue stress, periodontal ligament strain or root dentin tissue stress. Conclusion: The use of reinforcement inside the custom-made mouthguard can modify the stress generated in the enamel buccal surface without improvement to the root dentin, periodontal ligament or bone tissue.

scholarly journals Biomechanical Behavior Evaluation of a Novel Hybrid Occlusal Splint-mouthguard for Contact Sports: 3D-FEA

2021 ◽  
Author(s):  
Les Kalman ◽  
Amanda Maria de Oliveira Dal Piva ◽  
Talita Suelen de Queiroz ◽  
João Paulo Mendes Tribst
Keyword(s):  
Stress Concentration ◽  
Mechanical Response ◽  
Compressive Loading ◽  
Von Mises Stress ◽  
Occlusal Splint ◽  
Total Deformation ◽  
Contact Sports ◽  
Biomechanical Behavior ◽  
Custom Made ◽  
Von Mises

Orofacial injuries are common occurrences during contact sports activities; however, there is an absence of data regarding the performance of hybrid occlusal splint mouthguards, especially during compressive loading. To evaluate the total deformation and stress concentration, a skull model was selected and duplicated to receive two different designs of mouthguard devices: one model received a conventional custom-made mouthguard (MG) with 4-mm thickness and the other received a novel hybrid occlusal splint-mouthguard (HMG) with the same thickness. Both models were subdivided into finite elements. The frictionless contacts were used, and a nonlinear analysis was performed simulating the compressive loading in occlusion. The results were presented in von-Mises stress maps (MPa) and Total Deformation (mm). A higher stress concentration in teeth was observed for the model with the conventional MG, while the HMG design displayed a promising mechanical response with lower stress magnitude. The HMG de-sign displayed a higher magnitude of stress on its occlusal portion than the MG design. The hybrid mouthguard (HMG) reduced (1) jaw displacement during chewing and (2) the generated stresses in maxil-lary and mandibular teeth.

scholarly journals Mechanical response and pore pressure generation in granular filters subjected to uniaxial cyclic loading

2018 ◽  
Vol 55 (12) ◽  
pp. 1756-1768
Author(s):  
Jahanzaib Israr ◽  
Buddhima Indraratna
Keyword(s):  
Cyclic Loading ◽  
Pore Pressure ◽  
Pore Water ◽  
Mechanical Response ◽  
Pore Water Pressure ◽  
Axial Strain ◽  
Water Pressure ◽  
Internal Erosion ◽  
Excess Pore Water Pressure ◽  
Excess Pore

This paper presents results from a series of piping tests carried out on a selected range of granular filters under static and cyclic loading conditions. The mechanical response of filters subjected to cyclic loading could be characterized in three distinct phases; namely, (I) pre-shakedown, (II) post-shakedown, and (III) post-critical (i.e., the occurrence of internal erosion). All the permanent geomechanical changes such, as erosion, permeability variations, and axial strain developments, took place during phases I and III, while the specimen response remained purely elastic during phase II. The post-critical occurrence of erosion incurred significant settlement that may not be tolerable for high-speed railway substructures. The analysis revealed that a cyclic load would induce excess pore-water pressure, which, in corroboration with steady seepage forces and agitation due to dynamic loading, could then cause internal erosion of fines from the specimens. The resulting excess pore pressure is a direct function of the axial strain due to cyclic densification, as well as the loading frequency and reduction in permeability. A model based on strain energy is proposed to quantify the excess pore-water pressure, and subsequently validated using current and existing test results from published studies.

The role of geomechanical modeling in the measurement and understanding of geophysical data collected during carbon sequestration

2021 ◽  
Vol 40 (6) ◽  
pp. 413-417
Author(s):  
Chunfang Meng ◽  
Michael Fehler
Keyword(s):  
Pore Pressure ◽  
Fault Location ◽  
Mechanical Response ◽  
Fluid Pressure ◽  
Geophysical Data ◽  
Fluid Injection ◽  
Coupled Flow ◽  
Cap Rock ◽  
Stress And Deformation ◽  
Pressure Changes

As fluids are injected into a reservoir, the pore fluid pressure changes in space and time. These changes induce a mechanical response to the reservoir fractures, which in turn induces changes in stress and deformation to the surrounding rock. The changes in stress and associated deformation comprise the geomechanical response of the reservoir to the injection. This response can result in slip along faults and potentially the loss of fluid containment within a reservoir as a result of cap-rock failure. It is important to recognize that the slip along faults does not occur only due to the changes in pore pressure at the fault location; it can also be a response to poroelastic changes in stress located away from the region where pore pressure itself changes. Our goal here is to briefly describe some of the concepts of geomechanics and the coupled flow-geomechanical response of the reservoir to fluid injection. We will illustrate some of the concepts with modeling examples that help build our intuition for understanding and predicting possible responses of reservoirs to injection. It is essential to understand and apply these concepts to properly use geomechanical modeling to design geophysical acquisition geometries and to properly interpret the geophysical data acquired during fluid injection.

Quantifying the mechanical response of the Izaña area (Tenerife) to sustained groundwater withdrawal 

2021 ◽  
Author(s):  
Anthony Lamur ◽  
Silvio De Angelis ◽  
Rayco Marrero ◽  
Yan Lavallée ◽  
Pablo J. Gonzalez
Keyword(s):  
Mechanical Response ◽  
Water Saturation ◽  
Poisson Ratio ◽  
Porous Network ◽  
P Waves ◽  
Groundwater Exploitation ◽  
Horizontal Drilling ◽  
Surface Water Resources ◽  
Aquifer Systems ◽  
Wide Range

<p>Surface water resources on volcanic islands with moderate rainfall and relatively high permeability are usually scarce or non-existent. As such, life and local economies of these islands mostly relies on groundwater exploitation. It is therefore important to characterise the sustainability of volcanic aquifer systems. In short, an aquifer is deemed in equilibrium when the recharge rate equals or exceeds the exploitation rate. The Izaña area in Tenerife Island (Canary Islands, Spain) has been exploited since the 1900s via a series of ~30 horizontal drilling or water galleries coming from both flanks of the NE-Ridge. Since exploitation began, the water table has dropped continuously, in some area even more than 200 m. Since the 2000s, aquifer dynamics (compaction) have been observed using InSAR indicating a subsidence rate of up to 2 cm per year.</p><p>Here, we investigate a suite of rock samples collected. The samples were collected at several water galleries aiming to be representative of the aquifer materials from the Izaña area. We first characterise the basic physical properties of each samples (porosity, permeability, solid density) before quantifying the elastic parameters (Young’s modulus, Poisson ratio) and uniaxial strength of the lithologies collected. We also measure V<sub>p</sub> under dry and wet conditions (i.e. different saturation levels) to assess whether water saturation can alter the velocity of P-waves passing through those rocks.</p><p>Preliminary results show that connected porosities range from 0.16 to 45%, conferring a wide range of mechanical response to increasing effective pressure, with strength ranging from 18 – 315 MPa and Young’s moduli ranging from 3 – 57 GPa. In a similar fashion, results for V<sub>p</sub> measurements also exhibit a range of values (~1.5 – 4.5 km/s). These data show that materials present in the aquifer are extremely varied, suggesting that both fluid flow and observed deformation are likely to be controlled by the weakest, most porous lithologies.</p><p>These results will further be integrated with the lithostratigraphic record of the aquifer in order to model the mechanical response of the aquifer to changes in effective pressures, and specifically pore pressure reduction with water extraction. Additionally, chemical and textural analysis will provide insights on the evolution of the porous network at different alteration levels, here serving as a proxy for time at saturation in the aquifer. Finally, we aim to compare the experimental results from laboratory measurements to those of hydro-geophysical measurements that will be collected in the field starting in mid-2021.</p>

Determination of Poisson’s Ratio by Spherical Indentation Using Neural Networks—Part I: Theory

2000 ◽  
Vol 68 (2) ◽  
pp. 218-223 ◽  
Author(s):  
N. Huber ◽  
A. Konstantinidis ◽  
Ch. Tsakmakis
Keyword(s):  
Poisson Ratio ◽  
Indentation Test ◽  
Inverse Function ◽  
Elastic Half Space ◽  
Spherical Indentation ◽  
Isotropic Hardening ◽  
Plastic Yield ◽  
Load Response ◽  
Reduced Modulus

When studying analytically the penetration of an indenter of revolution into an elastic half-space use is commonly made of the fraction Er=E/1−ν2. Because of this, only Er is determined from the indentation test, while the value of ν is usually assumed. However, as shown in the paper, if plastic deformation is involved during loading, the depth-load trajectory depends on the reduced modulus and, additionally, on the Poisson ratio explicitly. The aim of the paper is to show, with reference to a simple plasticity model exhibiting linear isotropic hardening, that the Poisson ratio can be determined uniquely from spherical indentation if the onset of plastic yield is known. To this end, a loading and at least two unloadings in the plastic regime have to be considered. Using finite element simulations, the relation between the material parameters and the quantities characterizing the depth-load response is calculated pointwise. An approximate inverse function represented by a neural network is derived on the basis of these data.

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