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Results for “Shear Strength”

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At least 19 recordsLinked to original sources
PubMed1978

The shear strength of trabecular bone from the femur, and some factors affecting the shear strength of the cement-bone interface.

The shear strength of trabecular bone from the femur has been studied. In general, the strongest trabecular bone is found close to the cortico-cancellous junction, though its shear strength depends also on the relationship of the trabeculae to the plane of shear. Some factors affecting the shear strength of the cement-bone interface have been investigated. In vitro, maximal cement-bone interface shear strength is obtained by exposing and thoroughly cleaning strong trabecular bone, and then forcing onto it under pressure low viscosity cement.

Adhesiveness↗
PubMedDate not supplied

Shear strength of self-curing acrylic cement.

The average shearing strength of surgical Simplex P bone cement has been experimentally evaluated and found to be 5,762 plus or minus 180 psi. The average shearing strength for compact bone is about 10,000 psi. Therefore surgical Simplex P does not resist shear forces as well as compact bone and should not be used as a substitute for bone whenever possible. The inclusion of 10 per cent barium sulfate U.S.P. for radiographic purposes does not adversely affect the shear strength of the cement. This amount of barium is the same percentage by weight as that found in radiopaque Simplex P in clinical usage today. Varying the loading rate between 0.005 and 0.5 in/min slightly affected the magnitude of the shear force at failure. A comparison of the effect of short term curing times on the magnitude of the shear force at failure reveals that surgical Simplex P strengthens with time. The curing periods varied from 2 to 168 hours.

Acrylic Resins↗
PubMed1977

Bone-methyl methacrylate interfacial shear strength: an experimental study of dogs.

Bone-methyl methacrylate interfacial shear strength at failure in chronically implanted hip prostheses was studied. Gorman total hip prostheses fixed with methyl methacrylate bone cement were implanted in 6 large dogs. Interface shear strength studies were performed at 8, 16, and 24 weeks. Mechanical testing determined that the mean interfacial shear strength was 15.2 +/- 13.0 kg/cm2. Variability of the data was too great to allow conclusions to be drawn from statistical analysis, but trends in the data were observed. It was concluded that the interfacial bond had sufficient strength to withstand axial loads 3 to 6 times greater than those applied under normal physiologic conditions.

Animals↗
PubMed1976

Shear strength of orthodontic direct-bonding adhesives.

A total of 210 double-width stainless steel edgewise brackets with retentive lip bases were bonded to bovine incisors with seven commercially available direct-bonding materials. Ten samples for each of the seven direct-bonding materials were tested for shear strength using the Instron Universal Testing Instrument. The samples were tested after 1 day, 1 month, and 3 months of immersion in 30 per cent physiologic saline solution. The mean shear strength of each direct-bonding material at each time interval was compared statistically to the mean shear strength of each of the materials at each time interval with a matched 1 test. The same test was used to determine whether there had been a significant change in mean shear strength from start to finish of testing for each material. One product showed a significantly better mean shear strength than any other material at each test interval. The remaining materials were grouped in middle or low ranges, depending upon their final mean shear strengths and degrees of nonsignificance when compared to each other.

Acrylic Resins↗
PubMed1975

Some physical and mechanical factors affecting the simple shear strength of methylmethacrylate.

An investigation of the effect of kneading time on the simple shear strength of cold-cured plain methylmethacrylate bone cement and on the effect of anchor-hole configuration on the load-carrying capabilities of the cement anchor-hole configuration demonstrates that at a strain-rate of 10-3 rad/second, the mean simple shear strength of the cement was 251.65 (plus or minus 3%) for both 30-second and 2-minute kneading times. Increasing the loading rate to 10-1 rad/second increased the simple shear strength of 326.20 kg/cm-2 (plus or minus 2%). The geometric configuration did not significantly affect the maximum shear load-carrying capabilities of the methylmethacrylate.

Acetabulum↗
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↗
PubMed1992

A comparison of the shear strength of chemically versus electrolytically etched metal retainers.

The recent popularity of acid-etched, resin-bonded retainers (RBR) has initiated improvements in design, technique, and etching. This study compared the shear strength of chemically etched Biobond retainers with electrolytically etched retainers bonded to enamel using identical cement. Shear fracture loads were recorded using Instrom testing for all specimens. The mean fracture load for the electrolytically etched castings was greater than that of the chemically etched castings. Electrolytically etched specimens also recorded the greatest and the least fracture load values. These results indicated that, while there were significant differences between the two groups with greater shear strength values for electrolytic etching, there was also more variation in shear fracture load with electrolytic etching.

Acid Etching, Dental↗
PubMed1978

Punch shear strength of polycarboxylate cements.

Two general conclusions are drawn which apply to all the four commercial polycarboxylate cements: First, the effect of storage condition upon shear strength was much more pronounced after 24 hours than after 1 hour of storage time; second, the effect of storage condition was most extreme when the specimens were tested free of their matrices. Additionally some specific comparisons between the four products tested can be made based on differences of shear strength within the same experimental condition. The effect of confinement decreased in the following order: Boston greater than Bondal greater than PCA greater than Durelon. Sensitivity to storage conditions decreased in this order: Durelon greater than Bondal greater than PCA greater than Boston. Finally sensitivity to storage times decreased in the order Bondal greater than Durelon greater than Boston greater than PCA.

Acrylic Resins↗
PubMed1992

Shear strength of laboratory-processed composite resins bonded to a silane-coated nickel-chromium-beryllium alloy.

The shear bond strengths of three commercial laboratory curing composite resin veneers bonded to a nickel-chromium-beryllium alloy treated with the Silicoater system were evaluated. Two light-cured resins and one heat- and pressure-cured resin were evaluated. No statistically significant difference in bond strengths among the three resins was found. Microscopic analysis of the fracture surfaces indicated that all failures were complex and cohesive in nature within the resin and composite. On the basis of the shear bond strengths measured, any of the composite resin veneers tested appear to be clinically acceptable.

Acrylic Resins↗
PubMedDate not supplied

Dentin bond shear strength and microleakage for Syntac/Heliomolar: a comparison between the manufacturer's and total etch technique.

Recent improvements in formulation have led to significant improvements in the bond strength and clinical performance of dentin bonding agents. The growing interest in the concept of total etch prompted a comparison between manufacturer-recommended procedure and that of total etch for the product Syntac. An in vitro study to examine shear bond strength to dentin and microleakage and an in vivo component to investigate the micromorphologic relationship between restoration and tissue was conducted. No statistical significance was observed in bond strength values for the nonetched versus the etched group. Significantly, however, a larger number of specimens in the nonetched group exhibited microleakage. In vivo, only the etched group exhibited a zone of hybridization although both nonetched and etched restorations showed no interfacial gaps. It was concluded that total etch does not compromise the shear bond strength of Syntac but it appears to significantly reduce microleakage possibly due to the formation of a hybrid zone and may have merit clinically.

Acid Etching, Dental↗
PubMed1992

Shear strength of resin developed by four bonding agents used with cast metal restorations.

The evolution of the acid etch technique has made possible a more conservative approach to the fabrication of cast metal restorations. The resin bonding technique, however, places a greater burden for success on the selection of a bonding agent. This study examined the shear bond strength durability of cast metal restorations bonded to tooth structure with one of four metal adhesive bonding agents. Results indicated stronger bonds for restorations cemented with Panavia EX bonding agent than with any of the other bonding agents tested, both with and without exposure to thermal stress. Although it was one of the easier materials with which to work, Panavia EX bonding agent requires the additional step of applying an agent to prevent oxygen contact in the setting process.

Acid Etching, Dental↗
PubMedDate not supplied

The effects of barium sulfate on the polymerization temperature and shear strength of surgical simplex P.

Barium sulfate additive, in amounts ranging from 5% to 60%, causes a progressive reduction in polymerization temperature of the cement without appreciably altering the polymerization time. Concurrently, the mechanical strength of the cement, as determined in shear, decreases with increasing concentration of barium additive. Although inclusion of barium sulfate in acrylic bone cement is primarily used for radiographic contrast purposes, its possible effects on release of monomer and other local mechanisms seem not to have been measured.

Barium Sulfate↗
PubMed1992

Early uncovering of HA-coated cylinder implants: case report of an in vivo shear strength test.

A new approach was used to test the readiness of an HA-coated implant for commencement of prosthetic procedures after two months of bone healing in humans. A torquing device was used for clinical measurement of the shear resistance of the supporting bone. It was found that the bone was capable of resisting a shear force just slightly greater than that which was necessary to produce displacement of implants placed in dog femurs with a comparable bone-healing period and with healing to full maturity. This report suggests that it may be feasible to uncover HA-coated implants after two months of bone healing.

Dental Implants↗
PubMedDate not supplied

The effect of radiation on the shear strength of acrylic bone cement.

Bone loss due to secondary neoplastic disease of bone has frequently presented the orthopedic surgeon with difficult or insoluble problems of surgical management. Local radiation is the most effective, and widely used form of therapy for this type of metastatic disease. Levels of radiation in vitro comparable to therapeutic doses, as well as levels 6 times that commonly used in vivo on patients, demonstrate no significant effect on the mechanical properties of acrylic bone cement.

Acrylic Resins↗