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}
L. Heskin, R. Galvin, Jack Conroy, O. Traynor, Stephen Madden, C. Simms
INTRODUCTION The required fidelity of synthetic materials in surgical simulators to teach tissue handling and repair requirements should be as accurate as possible. There is a poor understanding of the relationship between choice of muscle surrogates and training outcome for trainee surgeons. To address this, the mechanical characteristics of several candidate synthetic muscle surrogates were measured, and their subjective biofidelity was qualitatively assessed by surgeons. METHODS Silicone was selected after assessing several material options and 16 silicone-based surrogates were evaluated. Three of the closest samples to muscle (Samples 1.1, 1.2, 1.3) and one with inserted longitudinal fibres (1.2F) were mechanically tested in the following: compression and tension, needle puncture force and suture pull-out in comparison with real muscle. The four samples were evaluated by 17 Plastic and Orthopaedic surgeons to determine their views of the fidelity with regard to the handling properties, needle insertion and ease of suture pull-out. RESULTS The mechanical testing showed the surrogates exhibited varying characteristics that matched some of the properties of muscle, though none recreated all the mechanical characteristics of native muscle. Good biofidelity was generally achieved for compression stiffness and needle puncture force, but it was evident that tensile stiff was too low for all samples. The pull-out forces were variable and too low, except for the sample with longitudinal fibres. In the qualitative assessment, the overall median scores for the four surrogate samples were all between 30 and 32 (possible range 9-45), indicating limited differentiation of the samples tested by the surgeons. CONCLUSIONS The surrogate materials showed a range of mechanical properties bracketing those of real muscle, thus presenting a suitable combination of candidates for use in simulators to attain the requirements as set out in the learning outcomes of muscle repair. However, despite significant mechanical differences between the samples, all surgeons found the samples to be similar to each other.
{"title":"Skeletal muscle surrogates for the acquisition of muscle repair skills in upper limb surgery.","authors":"L. Heskin, R. Galvin, Jack Conroy, O. Traynor, Stephen Madden, C. Simms","doi":"10.2139/ssrn.3998968","DOIUrl":"https://doi.org/10.2139/ssrn.3998968","url":null,"abstract":"INTRODUCTION\u0000The required fidelity of synthetic materials in surgical simulators to teach tissue handling and repair requirements should be as accurate as possible. There is a poor understanding of the relationship between choice of muscle surrogates and training outcome for trainee surgeons. To address this, the mechanical characteristics of several candidate synthetic muscle surrogates were measured, and their subjective biofidelity was qualitatively assessed by surgeons.\u0000\u0000\u0000METHODS\u0000Silicone was selected after assessing several material options and 16 silicone-based surrogates were evaluated. Three of the closest samples to muscle (Samples 1.1, 1.2, 1.3) and one with inserted longitudinal fibres (1.2F) were mechanically tested in the following: compression and tension, needle puncture force and suture pull-out in comparison with real muscle. The four samples were evaluated by 17 Plastic and Orthopaedic surgeons to determine their views of the fidelity with regard to the handling properties, needle insertion and ease of suture pull-out.\u0000\u0000\u0000RESULTS\u0000The mechanical testing showed the surrogates exhibited varying characteristics that matched some of the properties of muscle, though none recreated all the mechanical characteristics of native muscle. Good biofidelity was generally achieved for compression stiffness and needle puncture force, but it was evident that tensile stiff was too low for all samples. The pull-out forces were variable and too low, except for the sample with longitudinal fibres. In the qualitative assessment, the overall median scores for the four surrogate samples were all between 30 and 32 (possible range 9-45), indicating limited differentiation of the samples tested by the surgeons.\u0000\u0000\u0000CONCLUSIONS\u0000The surrogate materials showed a range of mechanical properties bracketing those of real muscle, thus presenting a suitable combination of candidates for use in simulators to attain the requirements as set out in the learning outcomes of muscle repair. However, despite significant mechanical differences between the samples, all surgeons found the samples to be similar to each other.","PeriodicalId":94117,"journal":{"name":"Journal of the mechanical behavior of biomedical materials","volume":"131 1","pages":"105216"},"PeriodicalIF":0.0,"publicationDate":"2022-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42557289","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}
A new CPC was developed in this study using a β-TCP powder mechano-chemically modified by ball-milling. The prototype CPC exhibits excellent fluidity for easy injection into bone defects; however, there is a risk of leakage from the defects immediately after implantation due to its high fluidity. The addition of poloxamer, an inverse thermoresponsive gelling agent, into CPC optimizes the fluidity. At lower temperatures, it forms a sol and maintains good injectability, whereas at the human body temperature, it transforms to a gel, reducing the fluidity and risk of leakage. In this study, the effects of poloxamer addition of 3, 5, and 10 mass% on the injectability, shape stability, and strength of the prototype CPC were evaluated. The calculated injectability of the prototype CPC pastes containing three different poloxamer contents was higher than that of the CPC paste without poloxamer for 15 min at 37 °C. Furthermore, the shape stability immediately after injection of the three CPC pastes with poloxamer was higher than that of the CPC paste without poloxamer. After 1 week of storage at 37 °C, the compressive strength and diametral tensile strength of the CPC compacts containing 10 mass% poloxamer were similar to those of the CPC compact without poloxamer. Additionally, the CPC compacts containing 10 mass% poloxamer exhibited clear plastic deformation after fracture. These results indicate that the addition of poloxamer to the prototype CPC could reduce the risk of leakage from bone defects and improve the fracture toughness with maintaining the injectability and strength.
{"title":"Effects of poloxamer additives on strength, injectability, and shape stability of beta-tricalcium phosphate cement modified using ball-milling.","authors":"Y. Kim, E. Uyama, K. Sekine, F. Kawano, K. Hamada","doi":"10.2139/ssrn.4041128","DOIUrl":"https://doi.org/10.2139/ssrn.4041128","url":null,"abstract":"A new CPC was developed in this study using a β-TCP powder mechano-chemically modified by ball-milling. The prototype CPC exhibits excellent fluidity for easy injection into bone defects; however, there is a risk of leakage from the defects immediately after implantation due to its high fluidity. The addition of poloxamer, an inverse thermoresponsive gelling agent, into CPC optimizes the fluidity. At lower temperatures, it forms a sol and maintains good injectability, whereas at the human body temperature, it transforms to a gel, reducing the fluidity and risk of leakage. In this study, the effects of poloxamer addition of 3, 5, and 10 mass% on the injectability, shape stability, and strength of the prototype CPC were evaluated. The calculated injectability of the prototype CPC pastes containing three different poloxamer contents was higher than that of the CPC paste without poloxamer for 15 min at 37 °C. Furthermore, the shape stability immediately after injection of the three CPC pastes with poloxamer was higher than that of the CPC paste without poloxamer. After 1 week of storage at 37 °C, the compressive strength and diametral tensile strength of the CPC compacts containing 10 mass% poloxamer were similar to those of the CPC compact without poloxamer. Additionally, the CPC compacts containing 10 mass% poloxamer exhibited clear plastic deformation after fracture. These results indicate that the addition of poloxamer to the prototype CPC could reduce the risk of leakage from bone defects and improve the fracture toughness with maintaining the injectability and strength.","PeriodicalId":94117,"journal":{"name":"Journal of the mechanical behavior of biomedical materials","volume":"130 1","pages":"105182"},"PeriodicalIF":0.0,"publicationDate":"2022-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46795075","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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