scholarly journals Viscoelastic properties of human periodontal ligament: Effects of the loading frequency and location

2019 ◽  
Vol 89 (3) ◽  
pp. 480-487 ◽  
Author(s):  
Bin Wu ◽  
Siyu Zhao ◽  
Haotian Shi ◽  
Ruxin Lu ◽  
Bin Yan ◽  
...  
Keyword(s):  
Periodontal Ligament ◽  
Viscoelastic Properties ◽  
Mechanical Response ◽  
Loss Modulus ◽  
Mechanical Analysis ◽  
Loading Frequency ◽  
Central Incisor ◽  
Dynamic Moduli ◽  
Tooth Position ◽  
Storage And Loss Moduli

ABSTRACT Objectives: To determine the viscoelastic properties of the human periodontal ligament (PDL) using dynamic mechanical analysis (DMA). Materials and Methods: This study was carried out on three human maxillary jaw segments containing six upper central incisors and four lateral incisors. DMA was used to investigate the mechanical response of the human PDL. Dynamic sinusoidal loading was carried out with an amplitude of 3 N and frequencies between 0.5 Hz and 10 Hz. All samples were grouped by tooth positions and longitudinal locations. Results: An increase of oscillation frequency resulted in marked changes in the storage and loss moduli of the PDL. The storage modulus ranged from 0.808 MPa to 7.274 MPa, and the loss modulus varied from 0.087 MPa to 0.891 MPa. The tanδ, representing the ratio between viscosity and elasticity, remained constant with frequency. The trends for storage and loss moduli were described by exponential fits. The dynamic moduli of the central incisor were higher than those of the lateral incisor. The PDL samples from the gingival third of the root showed lower storage and loss moduli than those from the middle third of the root. Conclusions: Human PDL is viscoelastic through the range of frequencies tested: 0.5–10 Hz. The viscoelastic relationship changed with respect to frequency, tooth position, and root level.

Properties of Mouse Cutaneous Rapidly Adapting Afferents: Relationship to Skin Viscoelasticity

2004 ◽  
Vol 92 (2) ◽  
pp. 1236-1240 ◽  
Author(s):  
P. Grigg ◽  
D. R. Robichaud ◽  
Z. Del Prete
Keyword(s):  
Viscoelastic Material ◽  
Material Properties ◽  
Viscoelastic Properties ◽  
Mechanical Response ◽  
Loss Modulus ◽  
Multiple Logistic Regression Analysis ◽  
Rate Of Change ◽  
Volterra Model ◽  
Lower Sensitivity ◽  
Dynamic Stimuli

When skin is stretched, stimuli experienced by a cutaneous mechanoreceptor neuron are transmitted to the nerve ending through the skin. In these experiments, we tested the hypothesis that the viscoelastic response of the skin influences the dynamic response of cutaneous rapidly adapting (RA) neurons. Cutaneous RA afferent neurons were recorded in 3 species of mice (Tsk, Pallid, and C57BL6) whose skin has different viscoelastic properties. Isolated samples of skin and nerve were stimulated mechanically with a dynamic stretch stimulus, which followed a pseudo Gaussian waveform with a bandwidth of 0–60 Hz. The mechanical response of the skin was measured as were responses of single RA cutaneous mechanoreceptor neurons. For each neuron, the strength of association between spike responses and the dynamic and static components of stimuli were determined with multiple logistic regression analysis. The viscoelastic material properties of each skin sample were determined indirectly, by creating a nonlinear (Wiener–Volterra) model of the stress–strain relationship, and using the model to predict the complex compliance (i.e., the viscoelastic material properties). The dynamic sensitivity of RA mechanoreceptor neurons in mouse hairy skin was weakly related to the viscoelastic properties of the skin. Loss modulus and phase angle were lower (indicating a decreased viscous component of response) in Tsk and Pallid than in C57BL6 mice. However, RA mechanoreceptor neurons in Tsk and Pallid skin did not differ from those in C57 skin with regard to their sensitivity to the rate of change of stress or to the rate of change of incremental strain energy. They did have a decreased sensitivity to the rate of change of tensile strain. Thus the skin samples with lower dynamic mechanical response contained neurons with a somewhat lower sensitivity to dynamic stimuli.

scholarly journals Dynamic Mechanical Analysis as a Complementary Technique for Stickiness Determination in Model Whey Protein Powders

Foods ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 1295
Author(s):  
Laura O’Donoghue ◽  
Md. Haque ◽  
Sean Hogan ◽  
Fathima Laffir ◽  
James O’Mahony ◽  
...  
Keyword(s):  
Glass Transition ◽  
Dynamic Mechanical Analysis ◽  
Whey Protein ◽  
Loss Modulus ◽  
Mechanical Analysis ◽  
Whey Protein Concentrate ◽  
Scanning Calorimetry ◽  
Dynamic Mechanical ◽  
Storage And Loss Moduli ◽  
Lower Protein

The α-relaxation temperatures (Tα), derived from the storage and loss moduli using dynamic mechanical analysis (DMA), were compared to methods for stickiness and glass transition determination for a selection of model whey protein concentrate (WPC) powders with varying protein contents. Glass transition temperatures (Tg) were determined using differential scanning calorimetry (DSC), and stickiness behavior was characterized using a fluidization technique. For the lower protein powders (WPC 20 and 35), the mechanical Tα determined from the storage modulus of the DMA (Tα onset) were in good agreement with the fluidization results, whereas for higher protein powders (WPC 50 and 65), the fluidization results compared better to the loss modulus results of the DMA (Tα peak). This study demonstrates that DMA has the potential to be a useful technique to complement stickiness characterization of dairy powders by providing an increased understanding of the mechanisms of stickiness.

Dynamic Mechanical Analysis of Fly Ash Filled Polyurea Elastomer

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Jing Qiao ◽  
Alireza V. Amirkhizi ◽  
Kristin Schaaf ◽  
Sia Nemat-Nasser
Keyword(s):  
Glass Transition ◽  
Fly Ash ◽  
Dynamic Mechanical Analysis ◽  
Volume Fraction ◽  
Loss Modulus ◽  
Mechanical Analysis ◽  
Temperature Dependent ◽  
Dynamic Mechanical ◽  
Storage And Loss Moduli ◽  
Temperature Superposition

In this work, the material properties of a series of fly ash/polyurea composites were studied. Dynamic mechanical analysis was conducted to study the effect of the fly ash volume fraction on the composite’s mechanical properties, i.e., on the material’s frequency- and temperature-dependent storage and loss moduli. It was found that the storage and loss moduli of the composite both increase as the fly ash volume fraction is increased. The storage and loss moduli of the composites relative to those of pure polyurea initially increase significantly with temperature and then slightly decrease or stay flat, attaining peak values around the glass transition region. The glass transition temperature (measured as the temperature at the maximum value of the loss modulus) shifted toward higher temperatures as the fly ash volume fraction increased. Additionally, we present the storage and loss moduli master curves for these materials obtained through application of the time-temperature superposition on measurements taken at a series of temperatures.

scholarly journals Viscoelastic Properties of Contemporary Bulk-fill Restoratives: A Dynamic-mechanical Analysis

2018 ◽  
Vol 43 (3) ◽  
pp. 307-314 ◽  
Author(s):  
JEX Ong ◽  
AU Yap ◽  
JY Hong ◽  
AH Eweis ◽  
NA Yahya
Keyword(s):  
Dynamic Mechanical Analysis ◽  
Storage Modulus ◽  
Loss Tangent ◽  
Viscoelastic Properties ◽  
Loss Modulus ◽  
Artificial Saliva ◽  
Mechanical Analysis ◽  
Distilled Water ◽  
Glass Ionomer ◽  
Dynamic Mechanical

SUMMARY This study investigated the viscoelastic properties of contemporary bulk-fill restoratives in distilled water and artificial saliva using dynamic mechanical analysis. The materials evaluated included a conventional composite (Filtek Z350), two bulk-fill composites (Filtek Bulk-fill and Tetric N Ceram), a bulk-fill giomer (Beautifil-Bulk Restorative), and two novel reinforced glass ionomer cements (Zirconomer [ZR] and Equia Forte [EQ]). The glass ionomer materials were also assessed with and without resin coating (Equia Forte Coat). Test specimens 12 × 2 × 2 mm of the various materials were fabricated using customized stainless-steel molds. After light polymerization/initial set, the specimens were removed from the molds, finished, measured, and conditioned in distilled water or artificial saliva at 37°C for seven days. The materials (n=10) were then subjected to dynamic mechanical testing in flexure mode at 37°C and a frequency of 0.1 to 10 Hz. Storage modulus, loss modulus, and loss tangent data were subjected to normality testing and statistical analysis using one-way analysis of variance/Dunnett's test and t-test at a significance level of p < 0.05. Mean storage modulus ranged from 3.16 ± 0.25 to 8.98 ± 0.44 GPa, while mean loss modulus ranged from 0.24 ± 0.03 to 0.65 ± 0.12 GPa for distilled water and artificial saliva. Values for loss tangent ranged from 45.7 ± 7.33 to 134.2 ± 12.36 (10−3). Significant differences in storage/loss modulus and loss tangent were observed between the various bulk-fill restoratives and two conditioning mediums. Storage modulus was significantly improved when EQ and ZR was not coated with resin.

Preparation and Viscoelastic Properties of Waterborne Polyurethane/Cellulose Nanocrystals Composites

2013 ◽  
Vol 771 ◽  
pp. 105-108 ◽  
Author(s):  
Qun Zhao ◽  
Ke Lu Yan
Keyword(s):  
Cellulose Nanocrystals ◽  
Viscoelastic Properties ◽  
Loss Modulus ◽  
Casting Process ◽  
Waterborne Polyurethane ◽  
Mechanical Analysis ◽  
Nanocomposite Films ◽  
Ultrasonic Dispersion ◽  
Mechanical Reinforcement ◽  
Power Law Equation

The objective of this work is to study the viscoelastic properties by which nanofillers produce mechanical reinforcement in polymers using dynamic mechanical analysis (DMA). To this purpose, waterborne polyurethane (WBPU) and cellulose nanocrystals (CNCs) composites films with various filler contents were prepared by ultrasonic dispersion followed by emulsion casting process. In frequency sweep tests, the storage modulus and loss modulus were recorded and modeled by the Power Law equation. CNCs precipitation significantly increased the steady state viscous properties of cellulose nanocoposite films but decreased the dynamic viscoelastic properties and frequency sensitivity of nanocomposite films.

Dynamic Viscoelastic Characterization of Bulk-fill Resin-based Composites and Their Conventional Counterparts

2020 ◽  
Vol 45 (2) ◽  
pp. 173-182 ◽  
Author(s):  
AU Yap ◽  
AH Eweis ◽  
NA Yahya
Keyword(s):  
Aqueous Solutions ◽  
Viscoelastic Properties ◽  
Loss Modulus ◽  
Water Solution ◽  
Artificial Saliva ◽  
High Stress ◽  
Mechanical Analysis ◽  
Significance Level ◽  
Post Hoc ◽  
The Impact

SUMMARY This study compared the viscoelastic properties of restorative and flowable bulk-fill resin-based composites (RBCs) with their conventional counterparts and evaluated the impact of aqueous solutions on viscoelastic properties. The materials examined included three conventional RBCs (Filtek Z350, Tetric N Ceram, and Beautifil II), three restorative bulk-fill RBCs (Filtek Bulk-Fill Restorative, Tetric N Ceram Bulk-Fill, and Beautifil Bulk-Fill Restorative) in addition to three flowable bulk-fill RBCs (Filtek Bulk-Fill Flowable, Tetric N Flow Bulk-Fill, and Beautifil Bulk-Fill Flowable). Beam-shaped specimens (12×2×2 mm) were fabricated using customized stainless-steel molds, finished, and measured. The specimens were randomly divided into four groups and conditioned in air (control), artificial saliva, 0.02 N citric acid, and 50% ethanol-water solution for seven days at 37°C. They were then subjected to dynamic mechanical analysis (n = 10) in flexure mode at 37°C with a frequency of 0.1 to 10 Hz. Storage modulus, loss modulus, and loss tangent data were subjected to statistical analysis using one-way analysis of variance/Tukey post hoc test at a significance level of α = 0.05. Viscoelastic properties of the RBCs were found to be product and conditioning medium dependent. For most RBCs, exposure to aqueous solutions, particularly an ethanol-water solution, degraded viscoelastic properties. With the exception of Filtek Bulk-Fill Restorative, bulk-fill restorative and flowable RBCs generally had significantly lower storage and loss modulus than their conventional counterparts regardless of conditioning medium. Conventional RBCs are thus favored over their bulk-fill counterparts, particularly for high-stress-bearing areas.

scholarly journals Mechanical testing of glutaraldehyde cross-linked mitral valves. Part two: Elastic and viscoelastic properties of chordae tendineae

2020 ◽  
pp. 095441192097593
Author(s):  
Matthew Constable ◽  
Rhiannon Northeast ◽  
Bernard M Lawless ◽  
Hanna E Burton ◽  
Vera Gramigna ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Material Properties ◽  
Viscoelastic Properties ◽  
Loss Modulus ◽  
Mechanical Analysis ◽  
Cross Linking ◽  
Chordae Tendineae ◽  
Mitral Valves ◽  
Lower Strain ◽  
The Mean

The aim of this study was to assess whether the mechanical properties of mitral valve chordae tendineae are sensitive to being cross-linked under load. A total 64 chordae were extracted from eight porcine hearts. Two chordae (posterior basal) from each heart were subjected to uniaxial ramp testing and six chordae (two strut, two anterior basal and two posterior basal) were subjected to dynamic mechanical analysis over frequencies between 0.5 and 10 Hz. Chordae were either cross-linked in tension or cross-linked in the absence of loading. Chordae cross-linked under load transitioned from high to low extension at a lower strain than cross-linked unloaded chordae (0.07 cf. 0.22), with greater pre-transitional (30.8 MPa cf. 5.78 MPa) and post-transitional (139 MPa cf. 74.1 MPa) moduli. The mean storage modulus of anterior strut chordae ranged from 48 to 54 MPa for cross-linked unloaded chordae, as compared to 53–61 MPa cross-linked loaded chordae. The mean loss modulus of anterior strut chordae ranged from 2.3 to 2.9 MPa for cross-linked unloaded chordae, as compared to 3.8–4.8 MPa cross-linked loaded chordae. The elastic and viscoelastic properties of chordae following glutaraldehyde cross-linking are dependent on the inclusion/exclusion of loading during the cross-linking process; with loading increasing the magnitude of the material properties measured.

Reinforcing MWCNTs to enhance viscoelastic properties of polyurethane nanocomposites by using nano DMA techniques

2020 ◽  
pp. 089270572093074 ◽  
Author(s):  
Dinesh Kumar ◽  
Navin Kumar ◽  
Prashant Jindal
Keyword(s):  
Composite Material ◽  
Storage Modulus ◽  
Viscoelastic Properties ◽  
High Strength ◽  
Mechanical Analysis ◽  
Elastic Behavior ◽  
Loading Frequency ◽  
Uniform Dispersion ◽  
Tan Δ ◽  
A Minor

Multi-walled carbon nanotubes (MWCNTs)-reinforced polyurethane (PU) composites were fabricated by using solution mixing technique followed by compression molding. Nano dynamic mechanical analysis was carried out to investigate the viscoelastic properties of PU/MWCNTs composites within a frequency range of 5–250 Hz. At higher frequencies (250 Hz), the storage modulus of PU/MWCNTs composites with 10 wt% loading of MWCNTs was enhanced by 148% in equivalence to pristine PU. An improvement of 13.3% in storage modulus was observed at a loading frequency of 250 Hz in comparison to that of a loading frequency of 75 Hz, which indicates that the effect of MWCNTs on storage modulus was more pronounced at higher frequencies. At 75 Hz, a minor composition of MWCNTs (3 wt%) was sufficient to reduce the value of tan δ from 0.20 to 0.15, indicating that the material becomes more elastic after reinforcing MWCNTs. This significant improvement in the mechanical behavior of composite material has been attributed to the uniform dispersion of MWCNTs, and their adhesion with PU molecules. Reported enhancement in the elastic behavior of PU composite will boost the applicability of PU-based composite material for the fabrication of high-strength boots, gloves, and jackets required to absorb high vibration frequencies experienced during conditions such as rock drilling.

Thermal Viscoelastic Analysis of 3D Fabric Nanocomposites

2008 ◽  
Vol 47-50 ◽  
pp. 1133-1136 ◽  
Author(s):  
Nan Jia Zhou ◽  
Andrey Beyle ◽  
Christopher C. Ibeh
Keyword(s):  
Thermal Analysis ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Loss Tangent ◽  
Viscoelastic Properties ◽  
Vinyl Ester ◽  
Loss Modulus ◽  
Viscoelastic Analysis ◽  
Storage And Loss Moduli

Viscoelastic properties of 3D fabric reinforced Vinyl Ester composites were studied in different directions using Dynamic Mechanical Thermal Analysis (DMTA). Such materials filled by nanoparticles (silicon carbide) with different concentrations were also investigated. The increases of storage and loss moduli with addition of nanoparticles and with increase of their concentrations were observed. The maximal tangent of the angle of mechanical losses was especially compared at below and over glass transition temperature. Below glass transition temperature the presence of nanoparticles increases storage and loss moduli and loss tangent. These effects achieved maximum at glass transition temperature. Over glass transition, the loss modulus and loss tangent are decreased with increase of the concentration of nanoparticles.

scholarly journals Mouthguard Use Effect on the Biomechanical Response of an Ankylosed Maxillary Central Incisor during a Traumatic Impact: A 3-Dimensional Finite Element Analysis

Life ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 294
Author(s):  
Alexandre Luiz Souto Borges ◽  
Amanda Maria de Oliveira Dal Piva ◽  
Laís Regiane da Silva Concílio ◽  
Tarcisio José de Arruda Paes-Junior ◽  
João Paulo Mendes Tribst
Keyword(s):  
Periodontal Ligament ◽  
Impact Analysis ◽  
Mechanical Response ◽  
Von Mises Stress ◽  
Situation Models ◽  
Central Incisor ◽  
Element Analysis ◽  
Maxillary Central Incisor ◽  
Von Mises ◽  
Traumatic Impact

(1) Background: Trauma is a very common experience in contact sports; however, there is an absence of data regarding the effect of athletes wearing mouthguards (MG) associated with ankylosed maxillary central incisor during a traumatic impact. (2) Methods: To evaluate the stress distribution in the bone and teeth in this situation, models of maxillary central incisor were created containing cortical bone, trabecular bone, soft tissue, root dentin, enamel, periodontal ligament, and antagonist teeth were modeled. One model received a MG with 4-mm thickness. Both models were subdivided into finite elements. The frictionless contacts were used and a nonlinear dynamic impact analysis was performed in which a rigid object hit the model at 1 m·s−1. For each model, an ankylosed periodontal ligament was simulated totaling 4 different situations. The results were presented in von-Mises stress maps. (3) Results: A higher stress concentration in teeth and bone was observed for the model without a MG and with ankylosed tooth (19.5 and 37.3 MPa, respectively); the most promising mechanical response was calculated for patients with healthy periodontal ligament and MG in position (1.8 and 7.8 MPa, respectively). (4) Conclusions: The MG’s use is beneficial for healthy and ankylosed teeth, since it acts by dampening the generated stresses in bone, dentin, enamel and periodontal ligament. However, patients with ankylosed tooth are more prone to root fracture even when the MG is in position compared to a healthy tooth.

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