Fracture toughness of Kevlar 29/poly(methyl methacrylate) composite materials for surgical implantations (original) (raw)
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Journal of Materials Science, 1986
A comparative study of the fracture behaviour of Kevlar 29 reinforced bone and dental cements is undertakeh using both linear elastic and non-linear elastic fracture mechanics approaches. Results from both approaches reflect improved fracture toughness at very low fibre contents. Flexural modulus is not apparently improved in either system, and flexural strength is only improved in the bone cement system probably because of poor interfacial bonding and the presence of voids in the dental cement. In all cases, however, bone cement is seen to be superior to dental cement. This is interpreted in terms of Smaller voids and better fibre distribution due to the lower viscosity of the bone cement material. When compared to carbon-polymethyl methacrylate (PMMA) cements, Kevlar 29 reinforced systems appear to be superior. More work is underway to optimize the properties of these systems with regard to structural parameters.
Mechanical properties of poly(methyl methacrylate) bone cements
Journal of Biomedical Materials Research, 1981
Samples of low viscosity poly(methy1 methacrylate) (PMMA), graphite reinforced PMMA, and graphite reinforced low viscosity PMMA were evaluated for their compression strength and fracture toughness. These results were compared with two currently used plain PMMA bone cements. There were no statistically significant differences in compression strength between the five cements. Graphite reinforcement of plain cement produced a 32% increase in fracture toughness over plain cement. Graphite reinforcement of low viscosity cement also produced a significant increase in toughness (31%) over low viscosity cement with fiber reinforcement. However, low viscosity cement demonstrated significantly less fracture toughness than plain PMMA. 10,893-906 (1976).
Journal of Biomedical Materials Research, 1989
A study of the fracture behavior of poly-(methyl methacrylate) (PMMA) bone cement reinforced with short ultra-highmolecular-weight polyethylene (Spectra 900) fibers is presented. Linear elastic and nonlinear elastic fracture mechanics results indicate that a significant reinforcing effect is obtained at fiber contents as low as 1% by weight, but beyond that concentration a plateau value is reached and the fracture toughness becomes insensitive to fiber content. The flexural strength and modulus are apparently not improved by the incorporation of polyethylene fibers in the acrylic cement, probably because of the presence of voids, the poor mixing practice and the weakness of the fiber/ matrix interfacial bond. The present polyethylene/ PMMA composite presents several advantages as compared to other composite cements , but overall the mechanical performance of this system resembles that of Kevlar 29/PMMA cement, with a few differences. Scanning electron microscopy reveals characteristic micromechanisms of energy absorption in Spectra 900/PMMA bone cement. A scheme for the strength of random fiber-reinforced composites, which is a simple extension of the Kelly and Tyson model for the strength of unidirectional composites, is presented and discussed. Young's modulus and the fracture toughness results are discussed in the framework of existing theories. More fundamental modeling treatments are needed in terms of fracture micromechanisms to understand and optimize the various mechanical properties with respect to structural parameters and cement preparation technique.
Size and boundary effects on notch tensile strength and fracture properties of PMMA bone cement
Polymer Testing, 2017
Poly (methyl methacrylate) bone cement is widely used for anchoring total joint replacements. In such an application, tensile and fracture properties of the cement are particularly important as they have strong implications for the stability of the implant in the bone bed and, hence, its life. Being a quasi-brittle material, it is to be expected that any mechanical property of bone cement would be size-dependent. This issue has not been addressed in the literature. In the present work, tests using modified wedge-splitting specimens were carried out to determine the size and boundary effects on the notch tensile strength () and on two fracture parameters, namely, specific fracture energy (), and characteristic length based on the notch tensile strength () of a widely used approved brand, Palacos ® R. Size and boundary effects, of varying magnitudes, on each of these properties were found. For example, 1) for geometrically-similar specimens (specimen height (W) was varied from 15 mm to 36 mm but ratio of length of the starter crack (a) to W was fixed), the general trend was marked decrease in σ NT with increase in W for a given a/W; and 2) for identical-sized specimens (W was fixed but a/W was varied from 0.06 to 0.81), the general trend was moderate decrease in G f with increase in a/W for a given W. A validated boundary effect model presented in the literature and results from some of the specimens used in the present experimental work were used to compute the size-independent specific fracture energy and transition ligament length of the cement brand to be 2096 N m-1 and 4 mm, respectively.
Egyptian Dental Journal
Aim of the study: This in vitro study was conducted to investigate the fracture strength and microleakage of simulated immature teeth reinforced with fiber post using two types of composite resin cement " total etch and self etch ". Materials and methods: Eighty freshly extracted maxillary central incisors were used in the study, they were divided into two groups (40 samples for each) according to the stage of root development (mature-immature), Then each group was subdivided into two subgroups (20 samples for each) according to the type of adhesive composite resin cement (RELY X TM U200 Automix) (3M ESPE Germany) self-adhesive and (Bifix QM) (Voco. GERMANY) total etch , Each subgroup was further divided into two classes (10 samples for each) according to subjecting the samples to thermocycling or not , Finally 5 samples from each class were tested for fracture strength by using universal testing machine and the other 5 samples of each class were tested for microleakage by using digital microscope. Results: The results of the fracture strength test showed that mature teeth showed higher fracture strength than simulated immature teeth. Total etch composite resin composite cement showed higher fracture strength than self etch cement. Finally the results showed that thermocycling affects negatively on fracture strength. As regard microleakage, the reults pointed out that no microleakage occurred in all tested groups. Conclusions: Fracture strength of mature teeth is more than immature teeth, using total etch composite resin cement give more fracture strength than self etch composite resin cement, thermocycling affects negatively the fracture strength for mature or immature endodontically treated teeth, no microleakage occurred irrespective to the state of restored root (mature or immature).
Journal of Oral Rehabilitation, 2003
The purpose of this study was to determine changes in flexural properties of resin cement under simulated resin-bonded fixed partial denture (RBFPD) clinical conditions using aqueous ageing and cyclic loading. Panavia F flexural modulus and strength were measured by static loading to failure after 48-h and 60-day aqueous ageing at 37°C with and without simulated cyclic occlusal loading. Panavia F sorption and solubility were also measured. Scanning electron microscopy (SEM) was used to characterize the morphology of the fractured surfaces. A two-factor ANOVA (P £ 0AE05) indicated that cyclic loading produced a significant increase in the flexural modulus with no significant effect on the flexural strength. Conversely, aqueous ageing time produced a significant decrease in flexural strength with no effect on the flexural modulus. The SEM fracture analysis indicated that resin matrix fracture occurred in static-aqueous specimens; while in the aqueous-cycled specimens, resin matrix fracture occurred in addition to an increasing proportion of filler ⁄ resin interface fracture. Collectively, these outcomes suggest that initial degradation under simulated resin cement clinical function may be related to breakdown of the filler ⁄ resin interface bond, which could contribute to in vivo RBFPD resin cement cohesive failure.
Journal of Physical …, 2009
Poly(methyl methacrylate) (PMMA) is the material of choice for denture base construction. In spite of its many good qualities, the application of PMMA as an ideal dental base material is still restricted by a few limitations. One of these is the difficulty in achieving intrinsic radiopacity in the material. The aim of the present study is to investigate the possibility of using barium titanate (BaTiO 3) as a radiopacifier in PMMA. The formulation used in this study composed of PMMA 89.5 wt%, BaTiO 3 10 wt% and benzoyl peroxide (BPO) 0.5 wt% as an initiator, methyl methacrylate (MMA) 90 wt% as a monomer and ethylene glycol dimethyl acrylate (EGDMA) 10 wt% as a cross-linking agent. The BaTiO 3 was treated by a silane coupling agent, 3-trimethoxysilylpropyl methacrylate (γ-MPS), prior to incorporation in the solid components (PMMA, BPO). The curing was carried out using a water bath at 78°C for 1.5 h. The samples were tested for fracture toughness before and after soaking for 28 days in simulated body fluid (SBF). Moreover, the morphology of the specimens was investigated by scanning electron microscope (SEM). The results showed that the neat PMMA possessed slightly higher fracture toughness properties than the PMMA composite, and after 28 days of immersion, the fracture toughness values were reduced by 4.8% and 3.4% for neat PMMA and PMMA composite, respectively.
Fracture Energy of Engineered Cementitious Composites
Proceedings
The aim of this paper is to present preliminary results regarding Engineered Cementitious Composites (ECC) and their behavior when experimentally assessing their fracture energy, by measuring the flexural tensile strength (limit of proportionality, residual). As a characteristic of a ductile material, fracture energy is an important parameter when assessing ECC post-cracking residual stresses. With 2% fibers addition in the mixtures, the crack width can be controlled and the material’s ability to bear a tensile strain-hardening capacity has been assessed. Ninety days flexural tensile strength tests were performed in order to obtain preliminary results on ECC prismatic specimens.