The trachea is a complex tissue made up of hyaline cartilage, fibrous tissue, and muscle fibers. Currently, the knowledge of microscopic structural organization of these components and their role in determining the tissue's mechanical response is very limited. The purpose of this study is to provide data on the microstructure of the tracheal components and its influence on tissue's mechanical response. Five bovine tracheae were used in this study. Adventitia, cartilage, mucosa/submucosa, and trachealis muscle layers were methodically cut out from the whole tissue. Second-harmonic generation(SHG) via multi-photon microscopy (MPM) enabled imaging of collagen fibers and muscle fibers. Simultaneously, a planar biaxial test rig was used to record the mechanical behavior of each layer. In total 60 samples were tested and analyzed. Fiber architecture in the adventitia and mucosa/submucosa layer showed high degree of anisotropy with the mean fiber angle varying from sample to sample. The trachealis muscle displayed neat layers of fibers organized in the longitudinal direction. The cartilage also displayed a structure of thick mesh-work of collagen type II organized predominantly towards the circumferential direction. Further, mechanical testing demonstrated the anisotropic nature of the tissue components. The cartilage was identified as the stiffest component for strain level < 20% and hence the primary load bearing component. The other three layers displayed a non-linear mechanical response which could be explained by the structure and organization of their fibers. This study is useful in enhancing the utilization of structurally motivated material models for predicting tracheal overall mechanical response.
{"title":"Microstructure and mechanics of the bovine trachea: Layer specific investigations through SHG imaging and biaxial testing.","authors":"Venkata Ayyalasomayajula, B. Skallerud","doi":"10.2139/ssrn.4088009","DOIUrl":"https://doi.org/10.2139/ssrn.4088009","url":null,"abstract":"The trachea is a complex tissue made up of hyaline cartilage, fibrous tissue, and muscle fibers. Currently, the knowledge of microscopic structural organization of these components and their role in determining the tissue's mechanical response is very limited. The purpose of this study is to provide data on the microstructure of the tracheal components and its influence on tissue's mechanical response. Five bovine tracheae were used in this study. Adventitia, cartilage, mucosa/submucosa, and trachealis muscle layers were methodically cut out from the whole tissue. Second-harmonic generation(SHG) via multi-photon microscopy (MPM) enabled imaging of collagen fibers and muscle fibers. Simultaneously, a planar biaxial test rig was used to record the mechanical behavior of each layer. In total 60 samples were tested and analyzed. Fiber architecture in the adventitia and mucosa/submucosa layer showed high degree of anisotropy with the mean fiber angle varying from sample to sample. The trachealis muscle displayed neat layers of fibers organized in the longitudinal direction. The cartilage also displayed a structure of thick mesh-work of collagen type II organized predominantly towards the circumferential direction. Further, mechanical testing demonstrated the anisotropic nature of the tissue components. The cartilage was identified as the stiffest component for strain level < 20% and hence the primary load bearing component. The other three layers displayed a non-linear mechanical response which could be explained by the structure and organization of their fibers. This study is useful in enhancing the utilization of structurally motivated material models for predicting tracheal overall mechanical response.","PeriodicalId":94117,"journal":{"name":"Journal of the mechanical behavior of biomedical materials","volume":"134 1","pages":"105371"},"PeriodicalIF":0.0,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44544399","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. Vander Linden, H. Fehervary, Laura Maes, N. Famaey
Planar biaxial testing is a popular experimental technique for characterizing and comparing biological soft tissues. A correct identification of the different stress states of the tissue sample is therefore essential. However, the difference between the zero-stress reference state and the sample state prior to the loading cycle caused by the mounting, preconditioning and preloading is often not considered. The importance of this difference, caused by prestretch, is investigated by simulating virtual planar biaxial experiments, either assuming an ideal test with a single deformation gradient or using finite element modeling to simulate a rake-based experiment. Multiple parameter fitting methods are used to estimate the material properties based on the available experimental data. These methods vary based on how they approximate the zero-stress state: either the prestretch is ignored, or the loads are zeroed after the preload has been reached, or the unknown prestretch values are included into the optimization function. The results reveal the high necessity of assessing the stress-free state when analyzing a planar biaxial test. The material fitting including the prestretch outperforms the other methods in terms of correctly describing the mechanical behavior of the tested material. It can be extended to correct for the boundary effects induced by the gripping mechanisms, providing a more accurate, yet more computationally expensive estimate of the material properties.
{"title":"An improved parameter fitting approach of a planar biaxial test including the experimental prestretch.","authors":"K. Vander Linden, H. Fehervary, Laura Maes, N. Famaey","doi":"10.2139/ssrn.4110915","DOIUrl":"https://doi.org/10.2139/ssrn.4110915","url":null,"abstract":"Planar biaxial testing is a popular experimental technique for characterizing and comparing biological soft tissues. A correct identification of the different stress states of the tissue sample is therefore essential. However, the difference between the zero-stress reference state and the sample state prior to the loading cycle caused by the mounting, preconditioning and preloading is often not considered. The importance of this difference, caused by prestretch, is investigated by simulating virtual planar biaxial experiments, either assuming an ideal test with a single deformation gradient or using finite element modeling to simulate a rake-based experiment. Multiple parameter fitting methods are used to estimate the material properties based on the available experimental data. These methods vary based on how they approximate the zero-stress state: either the prestretch is ignored, or the loads are zeroed after the preload has been reached, or the unknown prestretch values are included into the optimization function. The results reveal the high necessity of assessing the stress-free state when analyzing a planar biaxial test. The material fitting including the prestretch outperforms the other methods in terms of correctly describing the mechanical behavior of the tested material. It can be extended to correct for the boundary effects induced by the gripping mechanisms, providing a more accurate, yet more computationally expensive estimate of the material properties.","PeriodicalId":94117,"journal":{"name":"Journal of the mechanical behavior of biomedical materials","volume":"134 1","pages":"105389"},"PeriodicalIF":0.0,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44983151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiaoqing Zhang, Xinyue Ma, M. Liao, Fang Liu, Qiang Wei, Zhi-ying Shi, S. Mai, Jingwei He
With the aim to prepare Bis-GMA-free bulk-filled dental resin composite (DRC), Bis-GMA-free resin matrix was prepared by mixing Bis-EFMA with TEGDMA at two mass ratios (Bis-EFMA/TEGDMA = 50 wt/50 wt and 60 wt/40 wt), and the bulk-filled resin composites were then obtained by mixing resin matrix with silanated glass fillers at a mass ratio of 30 wt/70 wt. Bis-GMA based resin composites were used as control. Refractive indexes of resin matrixes were measured. Besides the depth of cure mentioned in ISO standard, double bond conversion (DC) and bottom/top Vickers hardness (VHN) ratio of resin composites were investigated to evaluate the curing depth. Physicochemical properties, such as flexural properties, volumetric shrinkage (VS), shrinkage stress (SS), water sorption (WS) and solubility (SL), and cytotoxicity of resin composites were tested and statistically analyzed (ANOVA, Tukey's, p = 0.05). The results showed that Bis-EFMA/TEGDMA resin matrixes had higher refractive indexes than Bis-GMA/TEGDMA resin matrixes. Viscosities of Bis-EFMA based DRCs were higher than Bis-GMA based DRCs. Bis-EFMA-based (50/50) DRC had comparable depth of cure, DC, and VHN as Bis-GMA-based (50/50) DRC (p > 0.05). Though Bis-EFMA/TEGDMA (60/40) had the highest refractive index in all resin matrix, the corresponding DRCs had the lowest depth of cure, DC, and bottom/top VHN ratio in all groups (p < 0.05). Replacing Bis-GMA with Bis-EFMA had no negative effect on flexural properties, WS and SL of DRCs, and could reduce VS and SS of DRCs. Results of CCK8 assay showed that all of DRCs had the same cytotoxicity (p > 0.05), and the thickness of sample had no influence on the cytotoxicity (p > 0.05). All the results indicated that Bis-EFMA could be used to replace Bis-GMA to prepare bulk-filled dental resin composites. According to the results of depth of cure, DC, and bottom/top VHN ratio, 50 wt/50 wt was more appropriate than 60 wt/40 wt as the mass ratio of Bis-EFMA and TEGDMA in the resin matrix for bulk-filled dental resin composites.
{"title":"Properties of Bis-GMA free bulk-filled resin composite based on high refractive index monomer Bis-EFMA.","authors":"Xiaoqing Zhang, Xinyue Ma, M. Liao, Fang Liu, Qiang Wei, Zhi-ying Shi, S. Mai, Jingwei He","doi":"10.2139/ssrn.4101073","DOIUrl":"https://doi.org/10.2139/ssrn.4101073","url":null,"abstract":"With the aim to prepare Bis-GMA-free bulk-filled dental resin composite (DRC), Bis-GMA-free resin matrix was prepared by mixing Bis-EFMA with TEGDMA at two mass ratios (Bis-EFMA/TEGDMA = 50 wt/50 wt and 60 wt/40 wt), and the bulk-filled resin composites were then obtained by mixing resin matrix with silanated glass fillers at a mass ratio of 30 wt/70 wt. Bis-GMA based resin composites were used as control. Refractive indexes of resin matrixes were measured. Besides the depth of cure mentioned in ISO standard, double bond conversion (DC) and bottom/top Vickers hardness (VHN) ratio of resin composites were investigated to evaluate the curing depth. Physicochemical properties, such as flexural properties, volumetric shrinkage (VS), shrinkage stress (SS), water sorption (WS) and solubility (SL), and cytotoxicity of resin composites were tested and statistically analyzed (ANOVA, Tukey's, p = 0.05). The results showed that Bis-EFMA/TEGDMA resin matrixes had higher refractive indexes than Bis-GMA/TEGDMA resin matrixes. Viscosities of Bis-EFMA based DRCs were higher than Bis-GMA based DRCs. Bis-EFMA-based (50/50) DRC had comparable depth of cure, DC, and VHN as Bis-GMA-based (50/50) DRC (p > 0.05). Though Bis-EFMA/TEGDMA (60/40) had the highest refractive index in all resin matrix, the corresponding DRCs had the lowest depth of cure, DC, and bottom/top VHN ratio in all groups (p < 0.05). Replacing Bis-GMA with Bis-EFMA had no negative effect on flexural properties, WS and SL of DRCs, and could reduce VS and SS of DRCs. Results of CCK8 assay showed that all of DRCs had the same cytotoxicity (p > 0.05), and the thickness of sample had no influence on the cytotoxicity (p > 0.05). All the results indicated that Bis-EFMA could be used to replace Bis-GMA to prepare bulk-filled dental resin composites. According to the results of depth of cure, DC, and bottom/top VHN ratio, 50 wt/50 wt was more appropriate than 60 wt/40 wt as the mass ratio of Bis-EFMA and TEGDMA in the resin matrix for bulk-filled dental resin composites.","PeriodicalId":94117,"journal":{"name":"Journal of the mechanical behavior of biomedical materials","volume":"134 1","pages":"105372"},"PeriodicalIF":0.0,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49247463","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-06-23DOI: 10.48550/arXiv.2206.11591
L. Hug, G. Dahan, S. Kollmannsberger, E. Rank, Z. Yosibash
Proximal humerus impacted fractures are of clinical concern in the elderly population. Prediction of such fractures by CT-based finite element methods encounters several major obstacles such as heterogeneous mechanical properties and fracture due to compressive strains. We herein propose to investigate a variation of the phase field method (PFM) embedded into the finite cell method (FCM) to simulate impacted humeral fractures in fresh frozen human humeri. The force-strain response, failure loads and the fracture path are compared to experimental observations for validation purposes. The PFM (by means of the regularization parameter ℓ0) is first calibrated by one experiment and thereafter used for the prediction of the mechanical response of two other human fresh frozen humeri. All humeri are fractured at the surgical neck and strains are monitored by Digital Image Correlation (DIC). Experimental strains in the elastic regime are reproduced with good agreement (R2=0.726), similarly to the validated finite element method (Dahan et al., 2022). The failure pattern and fracture evolution at the surgical neck predicted by the PFM mimic extremely well the experimental observations for all three humeri. The maximum relative error in the computed failure loads is 3.8%. To the best of our knowledge this is the first method that can predict well the experimental compressive failure pattern as well as the force-strain relationship in proximal humerus fractures.
{"title":"Predicting Fracture in the Proximal Humerus using Phase Field Models","authors":"L. Hug, G. Dahan, S. Kollmannsberger, E. Rank, Z. Yosibash","doi":"10.48550/arXiv.2206.11591","DOIUrl":"https://doi.org/10.48550/arXiv.2206.11591","url":null,"abstract":"Proximal humerus impacted fractures are of clinical concern in the elderly population. Prediction of such fractures by CT-based finite element methods encounters several major obstacles such as heterogeneous mechanical properties and fracture due to compressive strains. We herein propose to investigate a variation of the phase field method (PFM) embedded into the finite cell method (FCM) to simulate impacted humeral fractures in fresh frozen human humeri. The force-strain response, failure loads and the fracture path are compared to experimental observations for validation purposes. The PFM (by means of the regularization parameter ℓ0) is first calibrated by one experiment and thereafter used for the prediction of the mechanical response of two other human fresh frozen humeri. All humeri are fractured at the surgical neck and strains are monitored by Digital Image Correlation (DIC). Experimental strains in the elastic regime are reproduced with good agreement (R2=0.726), similarly to the validated finite element method (Dahan et al., 2022). The failure pattern and fracture evolution at the surgical neck predicted by the PFM mimic extremely well the experimental observations for all three humeri. The maximum relative error in the computed failure loads is 3.8%. To the best of our knowledge this is the first method that can predict well the experimental compressive failure pattern as well as the force-strain relationship in proximal humerus fractures.","PeriodicalId":94117,"journal":{"name":"Journal of the mechanical behavior of biomedical materials","volume":"134 1","pages":"105415"},"PeriodicalIF":0.0,"publicationDate":"2022-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47587060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
P. Lemoine, J. Acheson, S. McKillop, J. J. van den Beucken, Joanna Ward, A. Boyd, B. Meenan
The corrosion rate of Mg alloys is currently too high for viable resorbable implant applications. One possible solution is to coat the alloy with a hydroxyapatite (HA) layer to slow the corrosion and promote bone growth. As such coatings can be under severe stresses during implant insertion, we present a nano-mechanical and nano-tribological investigation of RF-sputtered HA films on AZ31 Mg alloy substrates. EDX and XRD analysis indicate that as-deposited coatings are amorphous and Ca-deficient whereas rapid thermal annealing results in c-axis orientation and near-stoichiometric composition. Analysis of the nanoindentation data using a thin film model shows that annealing increases the coating's intrinsic hardness (H) and strain at break (H/E) values, from 2.7 GPa to 9.4 GPa and from 0.043 to 0.079, respectively. In addition, despite being rougher, the annealed samples display better wear resistance; a sign that the rapid thermal annealing does not compromise their interfacial strength and that these systems have potential for resorbable bone implant applications.
{"title":"Nanoindentation and nano-scratching of hydroxyapatite coatings for resorbable magnesium alloy bone implant applications.","authors":"P. Lemoine, J. Acheson, S. McKillop, J. J. van den Beucken, Joanna Ward, A. Boyd, B. Meenan","doi":"10.2139/ssrn.4073499","DOIUrl":"https://doi.org/10.2139/ssrn.4073499","url":null,"abstract":"The corrosion rate of Mg alloys is currently too high for viable resorbable implant applications. One possible solution is to coat the alloy with a hydroxyapatite (HA) layer to slow the corrosion and promote bone growth. As such coatings can be under severe stresses during implant insertion, we present a nano-mechanical and nano-tribological investigation of RF-sputtered HA films on AZ31 Mg alloy substrates. EDX and XRD analysis indicate that as-deposited coatings are amorphous and Ca-deficient whereas rapid thermal annealing results in c-axis orientation and near-stoichiometric composition. Analysis of the nanoindentation data using a thin film model shows that annealing increases the coating's intrinsic hardness (H) and strain at break (H/E) values, from 2.7 GPa to 9.4 GPa and from 0.043 to 0.079, respectively. In addition, despite being rougher, the annealed samples display better wear resistance; a sign that the rapid thermal annealing does not compromise their interfacial strength and that these systems have potential for resorbable bone implant applications.","PeriodicalId":94117,"journal":{"name":"Journal of the mechanical behavior of biomedical materials","volume":"133 1","pages":"105306"},"PeriodicalIF":0.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46567917","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Russell Spiewak, A. Gosselin, Danil Merinov, R. Litvinov, J. Weisel, Valerie Tutwiler, P. Purohit
Blood clots form at the site of vascular injury to seal the wound and prevent bleeding. Clots are in tension as they perform their biological functions and withstand hydrodynamic forces of blood flow, vessel wall fluctuations, extravascular muscle contraction and other forces. There are several mechanisms that generate tension in a blood clot, of which the most well-known is the contraction/retraction caused by activated platelets. Here we show through experiments and modeling that clot tension is generated by the polymerization of fibrin. Our mathematical model is built on the hypothesis that the shape of fibrin monomers having two-fold symmetry and off-axis binding sites is ultimately the source of inherent tension in individual fibers and the clot. As the diameter of a fiber grows during polymerization the fibrin monomers must suffer axial twisting deformation so that they remain in register to form the half-staggered arrangement characteristic of fibrin protofibrils. This deformation results in a pre-strain that causes fiber and network tension. Our results for the pre-strain in single fibrin fibers is in agreement with experiments that measured it by cutting fibers and measuring their relaxed length. We connect the mechanics of a fiber to that of the network using the 8-chain model of polymer elasticity. By combining this with a continuum model of swellable elastomers we can compute the evolution of tension in a constrained fibrin gel. The temporal evolution and tensile stresses predicted by this model are in qualitative agreement with experimental measurements of the inherent tension of fibrin clots polymerized between two fixed rheometer plates. These experiments also revealed that increasing thrombin concentration leads to increasing internal tension in the fibrin network. Our model may be extended to account for other mechanisms that generate pre-strains in individual fibers and cause tension in three-dimensional proteinaceous polymeric networks.
{"title":"Biomechanical origins of inherent tension in fibrin networks.","authors":"Russell Spiewak, A. Gosselin, Danil Merinov, R. Litvinov, J. Weisel, Valerie Tutwiler, P. Purohit","doi":"10.2139/ssrn.4097566","DOIUrl":"https://doi.org/10.2139/ssrn.4097566","url":null,"abstract":"Blood clots form at the site of vascular injury to seal the wound and prevent bleeding. Clots are in tension as they perform their biological functions and withstand hydrodynamic forces of blood flow, vessel wall fluctuations, extravascular muscle contraction and other forces. There are several mechanisms that generate tension in a blood clot, of which the most well-known is the contraction/retraction caused by activated platelets. Here we show through experiments and modeling that clot tension is generated by the polymerization of fibrin. Our mathematical model is built on the hypothesis that the shape of fibrin monomers having two-fold symmetry and off-axis binding sites is ultimately the source of inherent tension in individual fibers and the clot. As the diameter of a fiber grows during polymerization the fibrin monomers must suffer axial twisting deformation so that they remain in register to form the half-staggered arrangement characteristic of fibrin protofibrils. This deformation results in a pre-strain that causes fiber and network tension. Our results for the pre-strain in single fibrin fibers is in agreement with experiments that measured it by cutting fibers and measuring their relaxed length. We connect the mechanics of a fiber to that of the network using the 8-chain model of polymer elasticity. By combining this with a continuum model of swellable elastomers we can compute the evolution of tension in a constrained fibrin gel. The temporal evolution and tensile stresses predicted by this model are in qualitative agreement with experimental measurements of the inherent tension of fibrin clots polymerized between two fixed rheometer plates. These experiments also revealed that increasing thrombin concentration leads to increasing internal tension in the fibrin network. Our model may be extended to account for other mechanisms that generate pre-strains in individual fibers and cause tension in three-dimensional proteinaceous polymeric networks.","PeriodicalId":94117,"journal":{"name":"Journal of the mechanical behavior of biomedical materials","volume":"133 1","pages":"105328"},"PeriodicalIF":0.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43903958","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alexandre Hamma, J. Boisson, V. Serantoni, J. Dallard
In this paper, a visco-hyperelastic model representing the mechanical behavior of the human mandibular periosteum as an anisotropic and homogeneous material is identified. Different models, extracted from the literature, are tested and associated in order to describe the elastic and visco-elastic contributions of the cellular matrix on one hand and the collagen fibers on the other hand. The parameters of these models are determined using five human mandibular periosteum. Each harvested sample is cut and tested, at two different velocities, either longitudinally or transversely to collagen fibers main direction. The hyperelastic and visco-elastic contributions of the cellular matrix are extracted using tensile tests performed transversely. The hyperelastic and visco-elastic contributions of the collagen fibers are extracted using tensile tests performed longitudinally. In a second time, the identified combination of models is validated using twelve samples only tested longitudinally. The selected combination uses the simplified Rivlin's 2nd order law to model the hyper-elasticity of the cellular matrix, the Kulkarni's law to model its visco-elasticity contribution, and the Kulkarni's laws to model the whole contributions of collagen fibers.
{"title":"Identification of a visco-hyperelastic model for mandibular periosteum.","authors":"Alexandre Hamma, J. Boisson, V. Serantoni, J. Dallard","doi":"10.2139/ssrn.4093629","DOIUrl":"https://doi.org/10.2139/ssrn.4093629","url":null,"abstract":"In this paper, a visco-hyperelastic model representing the mechanical behavior of the human mandibular periosteum as an anisotropic and homogeneous material is identified. Different models, extracted from the literature, are tested and associated in order to describe the elastic and visco-elastic contributions of the cellular matrix on one hand and the collagen fibers on the other hand. The parameters of these models are determined using five human mandibular periosteum. Each harvested sample is cut and tested, at two different velocities, either longitudinally or transversely to collagen fibers main direction. The hyperelastic and visco-elastic contributions of the cellular matrix are extracted using tensile tests performed transversely. The hyperelastic and visco-elastic contributions of the collagen fibers are extracted using tensile tests performed longitudinally. In a second time, the identified combination of models is validated using twelve samples only tested longitudinally. The selected combination uses the simplified Rivlin's 2nd order law to model the hyper-elasticity of the cellular matrix, the Kulkarni's law to model its visco-elasticity contribution, and the Kulkarni's laws to model the whole contributions of collagen fibers.","PeriodicalId":94117,"journal":{"name":"Journal of the mechanical behavior of biomedical materials","volume":"133 1","pages":"105323"},"PeriodicalIF":0.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41466209","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Baixuan Yang, A. Irastorza-Landa, P. Heuberger, H. Ploeg
Maximum insertion torque (IT) for threaded dental implants is a primary clinical measurement to assess implant anchorage, and strongly influences the clinical outcome. Insertion torque is influenced by surgical technique, implant designs, and patient factors such as bone density and quality. In this study, an analytical model was proposed for IT to estimate contributions from the thread and taper separately. The purpose of this study was to test if the analytical model could 1. differentiate the parallel-walled and tapered implant; and, 2. represent four factors: bone surrogate density, drill protocol, implant surface finish and cutting flute. The IT was modeled as the sum of the torques from the thread's inclined plane and interface shear stress from the tapered body integrated over the surface area, respectively, with two main parameters: effective force, F', F' and effective pressure, p'. The effective force, relates to the clamping force from the thread, while the effective pressure, p', associates with the contact pressure at the bone-implant interface. The model performed well (R2 = 0.88-1.0) and differentiated between the parallel-walled (p'= 0) and tapered implants (p'= 0.12). The model's parameters could individually represent the effects of the four factors. High bone surrogate density, two-step drill protocol, and rough surface increased both F' and p'. The cutting flute had opposing effects on F' and p' (β4 = 0.35 and -0.24, respectively); and therefore, had the lowest net effect on IT. The proposed analytical model therefore improves the understanding of the principal contributors to dental implant IT by considering thread and taper mechanics independently.
{"title":"Analytical model for dental implant insertion torque.","authors":"Baixuan Yang, A. Irastorza-Landa, P. Heuberger, H. Ploeg","doi":"10.2139/ssrn.4034460","DOIUrl":"https://doi.org/10.2139/ssrn.4034460","url":null,"abstract":"Maximum insertion torque (IT) for threaded dental implants is a primary clinical measurement to assess implant anchorage, and strongly influences the clinical outcome. Insertion torque is influenced by surgical technique, implant designs, and patient factors such as bone density and quality. In this study, an analytical model was proposed for IT to estimate contributions from the thread and taper separately. The purpose of this study was to test if the analytical model could 1. differentiate the parallel-walled and tapered implant; and, 2. represent four factors: bone surrogate density, drill protocol, implant surface finish and cutting flute. The IT was modeled as the sum of the torques from the thread's inclined plane and interface shear stress from the tapered body integrated over the surface area, respectively, with two main parameters: effective force, F', F' and effective pressure, p'. The effective force, relates to the clamping force from the thread, while the effective pressure, p', associates with the contact pressure at the bone-implant interface. The model performed well (R2 = 0.88-1.0) and differentiated between the parallel-walled (p'= 0) and tapered implants (p'= 0.12). The model's parameters could individually represent the effects of the four factors. High bone surrogate density, two-step drill protocol, and rough surface increased both F' and p'. The cutting flute had opposing effects on F' and p' (β4 = 0.35 and -0.24, respectively); and therefore, had the lowest net effect on IT. The proposed analytical model therefore improves the understanding of the principal contributors to dental implant IT by considering thread and taper mechanics independently.","PeriodicalId":94117,"journal":{"name":"Journal of the mechanical behavior of biomedical materials","volume":"131 1","pages":"105223"},"PeriodicalIF":0.0,"publicationDate":"2022-04-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43684791","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
OBJECTIVES The aim of the study was to assess the applicability of the Weibull model for resin-based composites (RBC) to predict the outcome of different flexural tests based on one another, while identifying the minimal sample number for a precise Weibull representation. METHODS Four RBCs underwent 3-point, 4-point and biaxial flexural testing (n = 480). Fracture surfaces of all specimens were assessed under optical microscope, while fracture modes of the uniaxial specimens were documented. Representative specimens for each fracture mode were further analyzed under scanning electron microscope. Since fracture predominantly originated from a surface flaw, the effective surface was used in the Weibull model. The analysis was performed on 20, then 30 and finally 40 specimens per group to assess the effect of the specimen size. Further statistical analysis was performed through uni- and multivariate ANOVA, Tukey's post hoc test (α = 0.05), and Pearson's correlation. RESULTS The Weibull model could predict the results of uniaxial tests within the standard deviation, with the correlation between calculated and measured values reaching values of R2 = 0.985 and higher. Predictions for or based on the biaxial tests misestimated the measured values, with a weaker correlation (R2 = 0.875) between measured and calculated flexural strength (FS). The fit of the data to the Weibull distribution improved with rising sample size resulting in better predictions of the FS when n = 40. SIGNIFICANCE The applicability of the Weibull model on RBCs allows accurate comparison between bending tests and their FS under consideration of the effective surface.
{"title":"Prediction of uniaxial and biaxial flexural strengths of resin-based composites using the Weibull model.","authors":"Raluca Ghelbere, N. Ilie","doi":"10.2139/ssrn.4045919","DOIUrl":"https://doi.org/10.2139/ssrn.4045919","url":null,"abstract":"OBJECTIVES\u0000The aim of the study was to assess the applicability of the Weibull model for resin-based composites (RBC) to predict the outcome of different flexural tests based on one another, while identifying the minimal sample number for a precise Weibull representation.\u0000\u0000\u0000METHODS\u0000Four RBCs underwent 3-point, 4-point and biaxial flexural testing (n = 480). Fracture surfaces of all specimens were assessed under optical microscope, while fracture modes of the uniaxial specimens were documented. Representative specimens for each fracture mode were further analyzed under scanning electron microscope. Since fracture predominantly originated from a surface flaw, the effective surface was used in the Weibull model. The analysis was performed on 20, then 30 and finally 40 specimens per group to assess the effect of the specimen size. Further statistical analysis was performed through uni- and multivariate ANOVA, Tukey's post hoc test (α = 0.05), and Pearson's correlation.\u0000\u0000\u0000RESULTS\u0000The Weibull model could predict the results of uniaxial tests within the standard deviation, with the correlation between calculated and measured values reaching values of R2 = 0.985 and higher. Predictions for or based on the biaxial tests misestimated the measured values, with a weaker correlation (R2 = 0.875) between measured and calculated flexural strength (FS). The fit of the data to the Weibull distribution improved with rising sample size resulting in better predictions of the FS when n = 40.\u0000\u0000\u0000SIGNIFICANCE\u0000The applicability of the Weibull model on RBCs allows accurate comparison between bending tests and their FS under consideration of the effective surface.","PeriodicalId":94117,"journal":{"name":"Journal of the mechanical behavior of biomedical materials","volume":"131 1","pages":"105231"},"PeriodicalIF":0.0,"publicationDate":"2022-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47325095","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. Koch, Ole Thaden, Stefan Conrad, Kevin Tröndle, G. Finkenzeller, R. Zengerle, Sabrina Kartmann, S. Zimmermann, P. Koltay
The generation of artificial human tissue by 3D-bioprinting has expanded significantly as a clinically relevant research topic in recent years. However, to produce a complex and viable tissue, in-depth biological understanding and advanced printing techniques are required with a high number of process parameters. Here, we systematically evaluate the process parameters relevant for a hybrid bioprinting process based on fused-deposition modeling (FDM) of thermoplastic material and microextrusion of a cell-laden hydrogel. First, we investigated the effect of the printing temperature of polycaprolactone (PCL), on the junction strength between individual fused filaments and on the viability of immortalized mesenchymal stem cells (iMSC) in the surrounding alginate-gelatin-hydrogel. It was found that a printing temperature of 140 °C and bonds with an angle of 90° between the filaments provided a good compromise between bonding strength of the filaments and the viability of the surrounding cells. Using these process parameters obtained from individual fused filaments, we then printed cubic test structures with a volume of 10 × 10 × 10 mm3 with different designs of infill patterns. The variations in mechanical strength of these cubes were measured for scaffolds made of PCL-only as well as for hydrogel-filled PCL scaffolds printed by alternating hybrid bioprinting of PCL and hydrogel, layer by layer. The bare scaffolds showed a compressive modulus of up to 6 MPa, close to human hard tissue, that decreased to about 4 MPa when PCL was printed together with hydrogel. The scaffold design suited best for hybrid printing was incubated with cell-laden hydrogel and showed no degradation of its mechanical strength for up to 28 days.
{"title":"Mechanical properties of polycaprolactone (PCL) scaffolds for hybrid 3D-bioprinting with alginate-gelatin hydrogel.","authors":"F. Koch, Ole Thaden, Stefan Conrad, Kevin Tröndle, G. Finkenzeller, R. Zengerle, Sabrina Kartmann, S. Zimmermann, P. Koltay","doi":"10.2139/ssrn.3962819","DOIUrl":"https://doi.org/10.2139/ssrn.3962819","url":null,"abstract":"The generation of artificial human tissue by 3D-bioprinting has expanded significantly as a clinically relevant research topic in recent years. However, to produce a complex and viable tissue, in-depth biological understanding and advanced printing techniques are required with a high number of process parameters. Here, we systematically evaluate the process parameters relevant for a hybrid bioprinting process based on fused-deposition modeling (FDM) of thermoplastic material and microextrusion of a cell-laden hydrogel. First, we investigated the effect of the printing temperature of polycaprolactone (PCL), on the junction strength between individual fused filaments and on the viability of immortalized mesenchymal stem cells (iMSC) in the surrounding alginate-gelatin-hydrogel. It was found that a printing temperature of 140 °C and bonds with an angle of 90° between the filaments provided a good compromise between bonding strength of the filaments and the viability of the surrounding cells. Using these process parameters obtained from individual fused filaments, we then printed cubic test structures with a volume of 10 × 10 × 10 mm3 with different designs of infill patterns. The variations in mechanical strength of these cubes were measured for scaffolds made of PCL-only as well as for hydrogel-filled PCL scaffolds printed by alternating hybrid bioprinting of PCL and hydrogel, layer by layer. The bare scaffolds showed a compressive modulus of up to 6 MPa, close to human hard tissue, that decreased to about 4 MPa when PCL was printed together with hydrogel. The scaffold design suited best for hybrid printing was incubated with cell-laden hydrogel and showed no degradation of its mechanical strength for up to 28 days.","PeriodicalId":94117,"journal":{"name":"Journal of the mechanical behavior of biomedical materials","volume":"130 1","pages":"105219"},"PeriodicalIF":0.0,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42742733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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