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Results for “Shear Strength”

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PubMed2001

Shear strength and fatigue properties of human cortical bone determined from pure shear tests.

Shear properties of bone have been inferred from torsion tests. However, torsion often causes spiral fracture planes that correspond to tensile rather than shear failure. We measured the shear properties of human cortical bone in both longitudinal and transverse directions using pure shear tests. Shearing applied transverse to the bone long axis caused fracture along a 45 degrees plane that coincided with maximum tension. This fracture pattern is similar to spiral fractures caused by torsion. Shear strength along the bone axis was 51.6 MPa or about 35% less than that determined using torsion tests. Fatigue tests of human cortical bone in pure shear were conducted. The results agreed well with previous measurements of cortical bone fatigue life in tension and compression, when normalized to strength. Using tibial shear strain magnitudes measured previously for human volunteers, we estimated the fatigue life of cortical bone for different activities, and speculate that shear fatigue failure is a probable cause of tibial stress fractures resulting from impact loading.

Aged↗

PubMed1988

Reduction in cement-bone interface shear strength between primary and revision arthroplasty.

This study quantified changes in the cement-bone interface shear strength between primary and first- and second-revision arthroplasties as a function of mechanical interlock between the cement and bone. There were 128 segments obtained from four pairs of fresh human femora that were prepared sequentially as for primary and first and second revisions, taking care to maintain original canal morphology. Cement was pressurized into the cavity of the anatomic specimens, and the maximum interface shear strength between the cement plug and the bone was experimentally determined for each revision. First-revision interface shear strength was reduced to 20.6% of primary strength, and second revision strength to 6.8% of primary strength.

Adult↗

PubMed1990

Tensile and shear strength of orthodontic bracket bonding with glass ionomer cement and acrylic resin. An in vitro comparison.

The tensile and shear strength for a polyalkeonate luting cement (AquaCEM) and a no-mix acrylic resin (Unite) in orthodontic bracket bonding were compared in an in vitro test. Brackets bonded/cemented to extracted premolar teeth were subjected to loads in a universal testing apparatus and the dislodging forces were recorded. The possible influences of setting time and of bracket base design were also studied. No significant differences between the cement and the resin were found after allowing 24 hours of setting time. This in contrast to the significantly stronger tensile strength but inferior shear strength for the polyalkeonate cement when stress was applied after 15 minutes. A significantly higher tensile strength value was recorded for a foil-meshed bracket base type compared to an integral base type with cut grooves after 15 minutes, but not after 24 hours. While the polyalkeonate cement adhesion mostly fractured within the cement layer, the acrylic bond more often failed in the enamel-adhesive interface. The results support the use of the fluoride-containing cement as an alternative to acrylic adhesives in orthodontic bracket bonding, especially in high-risk caries patients.

Acrylic Resins↗

PubMed2003

[The measurement and comparison of shear fracture strength and shear bond strength between carbon fiber post and some other posts].

OBJECTIVE: The shear fracture strengths of carbon fiber post, IPS-Empress 2 all-ceramic post (without ZrO2 post), cast Ni-Cr alloy post, prefabricated zirconia ceramic post, human dentin and the shear bonding strengths of the first three kinds of post bonded in the human root canals were measured and compared, which are as the reference for dental clinic. METHODS: Standard cylindrical samples were made respectively in each group of carbon fiber post, IPS-Empress 2 all-ceramic post, cast Ni-Cr alloy post, prefabricated zirconia ceramic post, human dentin, three for each group. The shear fracture strengths of these samples were measured by universal testing machine (AUTOGRAPH DCS5000). Standard cylindrical samples were made respectively in each group of carbon fiber post, IPS-Empress 2 all-ceramic post (without ZrO2 post), cast Ni-Cr alloy post, five for each group. They were bonded in extracted human root canals that had been prepared to 3.0 mm length and 2.0 mm diameter with Glass ionomer cement (Japan Shofu). The shear bond strengths were measured by the same universal testing machine. RESULTS: The shear fracture strengths of the carbon fiber post (199MPa), cast Ni-Cr alloy post (210MPa, shear bend strength) and prefabricated zirconia ceramic post (193MPa) were statistically higher than those of IPS-Empress 2 all-ceramic post (109MPa) and human dentin (100MPa). The shear fracture strength of the carbon fiber post was statistically similar to that of cast Ni-Cr alloy post and prefabricated zirconia ceramic post. There were no statistical differences between the shear bond strengths of carbon fiber post (2.4MPa) and cast Ni-Cr alloy post (3.8MPa). IPS-Empress 2 all-ceramic post broke before debonding (2.7, break value). CONCLUSIONS: Carbon fiber post, as well as cast Ni-Cr alloy post and prefabricated zirconia ceramic post, has a comparatively high shear fracture strength. The shear bond strengths of carbon fiber post is similar to cast Ni-Cr alloy post.

Carbon↗

PubMed1995

Comparison of bone-implant interface shear strength of hydroxyapatite-coated and alumina-coated metal implants.

We performed a transcortical push-out test to determine the effect of surface roughness of hydroxyapatite (HA)-coated implants on bone-implant shear strength in a canine model. Hydroxyapatite- and alumina-coated SUS316L with the same surface roughness (roughness average: Ra = 5 microns) and HA-coated Ti-6A1-4V (Ra = 8.4 microns), sintered HA (Ra = 0.9 micron), and dense alumina (Ra = 1.3 microns) were inserted into the dog's femur. The interface shear strength of the dense alumina was significantly lower than that of other implants at both 4 and 12 weeks after implantation. At 4 weeks after implantation, the interface shear strength of the alumina-coated SUS316L was significantly lower than that of other implants (P < .05) except the dense alumina, but at 12 weeks, there was no significant difference between the implant types except the dense alumina. This indicates that the surface roughness of the HA coating affects the enhancement of the bone-implant interface shear strength at the early period after implantation, and that a surface roughness of several micrometers does not influence the bond strength between bone and HA. A scanning electron microscopic study indicated that in almost all cases at 12 weeks, the failure site after push-out testing was the coating-substrate interface, not the coating-bone interface. Therefore, protection of the coating-substrate interface from direct shear loading is needed.

Alloys↗

PubMed1999

Shear strength of the cement metal interface--an experimental study.

The shear strength of the cement-metal interface using rods with different surface treatments and a clinical standardized cementing technique was studied. Under "dry" conditions, a low interface shear strength can be obtained with polished and smooth CoCrMo surfaces (peak-to-valley height Rt: 1 microm, average 0.2 MPa; 5 microm, 0.38 MPa). Grit-blasted and polymethylmethacrylate (PMMA)-precoated surfaces achieved higher values (PMMA precoat: average 5.16 MPa; CoCrMo peak-to-valley height Rt: 20 microm, average 8.61 MPa: 60 microm, average 7.8 MPa). After immersion in physiological saline solution for 60 days, the PMMA-precoated rods kept their initial stability whereas all the other test rods had lost their stability completely. A microscopic analysis of cross-sections revealed gap formations at the cement-metal interface to varying degrees (1-16 microm). PMMA-precoated rods rarely showed any gap formation at all. The above-mentioned gap formation was seen independently of the porosity at the cement-metal interface and corresponds to the clinical and postmortem observed debonding of the interface.

Biomechanical Phenomena↗

PubMed1993

Penetration and shear strength of cement-bone interfaces in vivo.

Using sham replacement of the proximal femur in adult mongrel dogs, shear strength at the interface between polymethylmethacrylate bone cement and cancellous bone has been found to be linearly dependent on the depth of penetration of the cement into the bone. Shear strength at the interface was increased by 82% and penetration by 74% when distal bone plugging, pressure lavage, and pressurized insertion of cement were employed. Use of a lower-viscosity cement gave a further 18% increase in penetration and shear strength. There was no film of blood at the cement-bone interface with pressurized insertion of Simplex P and Palacos R cements.

Acrylic Resins↗

PubMed1993

The shear strength of polymethyl methacrylate bonded to titanium partial denture framework material.

Premachined titanium frameworks are used in implant-supported fixed complete-arch prostheses. Traditionally, retentive mechanisms are incorporated in the wax patterns to provide retention between polymethyl methacrylate and the cast framework. Nontraditional forms of retention are needed with machined frameworks. This study determined whether three different surface characteristics of titanium improve the bond shear strength of polymethyl methacrylate. Thirty rod shaped specimens of titanium were divided into three equal groups: group 1 received no pretreatment; group 2 was pretreated with 110 microns alumina air abrasive; and group 3 was pretreated with 110 microns alumina air abrasive plus silane (clear). Denture resin was processed around each specimen. A Shell-Nielsen shear test was then performed at a crosshead speed of 0.5 mm/minute to determine the bond shear strength in kilograms per square centimeter. The bond shear strength of group 3 was 63% greater than group 1 (significant, p < 0.01; ANOVA-Scheffé interval 63 kg/cm2). The results of this study indicated that surface pretreatment of titanium with 110 microns alumina air abrasive plus silane coating significantly enhances the bond shear strength of polymethyl methacrylate.

Aluminum Oxide↗

PubMed1986

Shear strength of loaded porous-glassy-carbon/bone interface--an experimental study on rabbits.

The aim of the study was to measure the shear strength of bone/porous-glassy-carbon interface in rabbit. Glassy carbon pellets were implanted into drill holes made through the medial articular surface of the proximal tibia of 15 rabbits. Shear strengths grew statistically significantly from 1 to 6 weeks and reached a maximum of 4.6 MN/m2. Microscopical examination of the sheared surfaces revealed that at 1 and 2 weeks the shearing occurred through the tissue surrounding the implant, and at 3, 6 and 12 weeks through the porous coating of the implant. To diminish the fragility of the porous coating, its porosity should be adjusted to 40%. Results of shear strength studies on current implant materials are reviewed.

Animals↗

PubMed2002

Determination of interfacial shear strength between the glass fiber and primary coating in double-coated optical fibers from mechanical strip forces.

We propose a method of determining interfacial shear strength between the glass fiber and primary coating in double-coated optical fibers. A commercial stripper is used to mechanically strip the polymeric coatings. It consists of two hinged arms and a pair of blades with a semicircular bore. In the mechanical stripping process the relationship between the strip force and stripper displacement is measured. The interfacial shear strength between the glass fiber and primary coating is then determined from this relationship. The measured interfacial shear strength increases with the increasing stripping rate. It is found that measured results are compatible with theoretical results.

Journal Article↗

PubMedDate not supplied

Shear strength of sealants placed with non-rinse conditioning compared to a conventional acid etch-rinse technique.

The present study compared the shearing strength of a non-rinse conditioning (NRC) compomer sealant to that of a conventional sealant. Thirty molars and premolars were sectioned longitudinally. The resulting halves were divided into 4 groups. Cylinders of sealants were bonded to the sections using a gelatin capsule as a matrix, as follows: Group A (n = 15) NRC + Prime & Bond + Dyract Seal; Group B (n = 15) same as group A but with phosphoric acid and rinse; Group C (n = 15) conventional phosphoric acid + Helioseal; Group D (n = 15) NRC + Helioseal. After immersing the specimens in water for 7 days, the samples were mounted on the Instron testing machine at a 20 mm/min crosshead speed. The results were subjected to ANOVA with Scheffe test, with a significant level of .05. No shearing strength values could be obtained for the specimens of group D. Some cylinders separated from the enamel while still immersed in the water, and in others the adhesion was too low, and no readings could be observed. For all groups, failure occurred at the sealant-enamel interface. The mean value for group A was 5.33 MPa, significantly less than that of groups B 9.12 MPa and C 9.63 MPa (p < 0.006). No significant difference of the mean shear strength was evident between groups B and C. No rinse conditioning with Dyract Seal led to a considerably lower bond strength value than Dyract Seal and Helioseal with phosphoric acid and rinsing.

Acid Etching, Dental↗

PubMed2005

[Study of shearing strength between layers of light curing composite Esterfill PHOTO].

There was determined shearing strength of monolit samples of light curing material and samples received by modeling of further layers on surfaces with and without inhibited layer and also tensile strength of layers connected with the help of light curing adhesive. The study was performed on enamel, dentine and cutting edge masses from set of light curing material Esterfill PHOTO for prosthetic purposes. The received results showed that shearing strength between layers of enamel, dentine and cutting edge masses of Esterfill PHOTO varied between 22 and 28 MPa and tensile force divided by the nominal surface area did not depend upon the way of sample modeling. Distraction zone represented half of the cone turn out of substrate. More rigid material chopped in the process of distraction lesser volume off substrate. For prosthetic purposes it was recommended to use the equipment allowing to combine the final photopolymerization of the article with annealing under high temperature conditions or make annealing of the ready article after photopolymerization.

Adhesiveness↗

PubMed1989

Shear strength and filler particle characterization of Maryland (acid etch) bridge resin cements.

The shear strengths of Maryland (acid etch) bridge cements were investigated and ranged from 44 to 70 MPa. The bulk shear strength of the resin cements is sufficient; the weak link in the system (other than the technique sensitivity) is the interface at or adjacent to the resin and metal or the resin and enamel. The resin cements were polished and etched, and scanning electron micrographs were taken and digitized to illustrate the filler particle sizes and distribution.

Acid Etching, Dental↗

PubMed2003

Factors affecting the static shear strength of the prosthetic stem-bone cement interface.

Debonding of the stem-cement interface has been implicated in the initiation of failure of cemented femoral stems. The objective of this work was to examine some of the parameters which influence the interface static shear strength, including surface finish, cement type, pre-treatments and porosity. Surface finish was found to have the greatest effect on the interface strength. Increasing the surface roughness by a factor of 100 increases the interface shear strength by a factor of 20. However, increasing the surface roughness above a certain value was found to have no additional affect. This was due to failure in the cement itself rather than at the cement-stem interface. There were significant differences between some of the different cement types regarding the interface strength. Pre-heating the stem produced a six fold reduction in cement porosity at the stem-cement interface, however, resulting in only a minor influence on the static interface strength. Generally, no significant correlation was found between the cement porosity and the static interfacial shear strength.

Journal Article↗

PubMed1976

Shear strength of the human femoral capital epiphyseal plate.

After the determination of the shear strength and modes of failure of the capital femoral epiphyseal plates in twenty-five pairs of hips obtained post mortem from children five days to fifteen years and ten months old, with the plate intact on one side and with the perichondrial fibrocartilaginous complex removed on the other, the gross and microscopic morphology was studied. The shear strength of the human epiphyseal plate varied with age and was greatly dependent on the surrounding perichondrial complex in infancy and early childhood, but less so in adolescence. When this complex was excised, the strength of the epiphyseal plate was diminished, especially in specimens from younger children. The forces necessary to cause slipping were found to be within the physiological range of the force that would be generated in overweight children, suggesting that purely mechanical factors may play a major role in the etiology of slipped capital femoral epiphysis.

Adolescent↗

PubMed1999

Interface shear strength of titanium implants with a sandblasted and acid-etched surface: a biomechanical study in the maxilla of miniature pigs.

The purpose of the present study was to evaluate the interface shear strength of unloaded titanium implants with a sandblasted and acid-etched (SLA) surface in the maxilla of miniature pigs. The two best documented surfaces in implant dentistry, the machined and the titanium plasma-sprayed (TPS) surfaces served as controls. After 4, 8, and 12 weeks of healing, removal torque testing was performed to evaluate the interface shear strength of each implant type. The results revealed statistically significant differences between the machined and the two rough titanium surfaces (p <.00001). The machined surface demonstrated mean removal torque values (RTV) between 0.13 and 0.26 Nm, whereas the RTV of the two rough surfaces ranged between 1.14 and 1.56 Nm. At 4 weeks of healing, the SLA implants yielded a higher mean RTV than the TPS implants (1.39 vs. 1. 14 Nm) without reaching statistical significance. At 8 and 12 weeks of healing, the two rough surfaces showed similar mean RTVs. The implant position also had a significant influence on removal torques for each implant type primarily owing to differences in density in the periimplant bone structure. It can be concluded that the interface shear strength of titanium implants is significantly influenced by their surface characteristics, since the machined titanium surface demonstrated significantly lower RTV in the maxilla of miniature pigs compared with the TPS and SLA surfaces.

Animals↗

PubMed2004

Prediction of interlaminar shear strength of a thermally aged carbon/epoxy composite material by Fourier transform infrared photoacoustic spectroscopy.

Photoacoustic spectroscopy was used to predict the interlaminar shear strength of a carbon/epoxy composite. Samples were artificially aged by exposing the samples to elevated temperatures in an air environment. Short-beam shear tests were performed to determine mechanically the interlaminar shear strength of the samples. Photoacoustic spectra of the samples were also collected and compared to mechanical data. Chemometrics were performed on the spectral and mechanical data, and a good correlation was found between the near surface chemistry of the composite and overall mechanical integrity.

Acoustics↗

PubMed2002

The effect of substrate roughness and hydroxyapatite coating thickness on implant shear strength.

This study examined the role of substrate preparation and hydroxyapatite (HA) coating thickness on bone ongrowth and shear strength in a bilateral bicortical sheep model. Plasma-sprayed and grit-blasted titanium implants with different thickness HA coatings were examined at 4, 8, 12, and 26 weeks after implantation. Shear strength increased with time for all implants. Plasma-sprayed implants were superior to grit-blasted implants at all time points. The 100-microm-thick HA layer used in the present study provided greater fixation and ongrowth and less resorption compared with the 50-microm-thick layer. We did not observe any advantage in using a thicker HA coating for the titanium substrates examined.

Analysis of Variance↗