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At least 19 recordsLinked to original sources
PubMed1975

Physical properties of experimental vitreous membranes. I. Tensile strength.

The tensile strength of vitreous membranes, induced by silk sutures imbedded in the vitreous body and removed one to two weeks later, was investigated in rabbits. Three types of membranes were distinguished by their appearance under an operating microscope; dense, opaque, cylindrical membranes, (Type 1), broken with 2 to 16 Gm. of force and elongated from 127 to 200 per cent before breaking; thin, cylindrical membranes, (Type 2), broken with 200 mg. to 2 Gm. of force and elongated from 51 to 152 per cent before breaking; and thin film-like membranes imbedded in formed vitreous gel, (Type 3), broken with 200 mg. to 5.5 Gm. of force and elongated from 53 to 186 per cent before breaking. Vitreous membranes formed two to eight weeks after surgery resisted forces greater than those required to detach rabbit retina. The results of the experiment are relevant in the design of vitrectomy instruments.

Animals↗
PubMed1975

Granulation tissue formation in oophorectomized rats treated with female sex hormones. II. Studies on the amount of collagen and on tensile strength.

The content of hydroxyproline and tensile strength of granulation tissue was studied in oophorectomized rats treated with female sex hormones. Estrogen alone caused a slight decrease of hydroxyproline, but had no effect on the tensile strength of the granulation tissue at one week. Progesterone alone or in combination with estrogen decreased the content of hydroxyproline and the tensile strength of the granulation tissue up to one week in the case of progesterone-treated animals and up to two weeks in the case of animals treated with the combination of the hormones. At one week no direct correlation was found between the amount of hydroxyproline and the tensile strength of granulation tissue in oophorectomized rats treated with estrogen and progesterone in combination.

Animals↗
PubMed1975

The effects of proteolytic enzymes on the tensile strength of human lung.

Human lung tissues were exposed to proteolytic enzymes to determine the effects on tensile strength and to clarify the relationship between tensile strength and the amounts of collagen and elastin in the tissue. Elastase and papain depleted the tissue of elastin but failed to alter tensile strength. Trypsin had no effect on tensile strength, or on collagen and elastin content. collagenase lowered tensile strength and reduced the amount of collagen in the tissue. The findings with collagenase were in agreement with measurements in control tissues that showed a direct relationship between tensile strength and collagen content. These results confirm collagen as the principal determinant of the tensile strength of human lung.

Aged↗
PubMed1992

Tensile strength of the interface between hydroxyapatite and bone.

Tensile strength of the interface between hydroxyapatite (HA) and bone was tested. Scanning electron microscopy was used to observe the tensile failure mode and the morphological change of hydroxyapatite ceramic surface in bone. The porosity of hydroxyapatite is 14% and pore size less than 2 microns. After 2 weeks of implantation, the tensile strength of the interface is 0.72 MPa. After 4, 8, and 16 weeks, the average tensile strength stayed at 1.5 MPa. SEM showed that tensile failure occurred at the HA-bone interface at the second week, but after 4 weeks, the failure occurred between HA particles within the bulk, and not at the HA-bone interface. Calcified tissue was directly deposited on the HA ceramic surface and exits also in the micropores. Near the interface, sintered necks among HA ceramic particles were subjected to biodegradation.

Animals↗
PubMed1976

The effect of anodic polarization on the tensile strength of dental amalgam.

The effect of corrosion upon dental amalgam was studied by measuring the effect of anodic polarization on its tensile strength. A conventional tensile testing method using dumb-bell shaped specimens deformed along the long axis was employed. The results showed a significant reduction (27%) in the mean tensile strength, due to the anodic polarization of conventional amalgam, whereas the strength of the high Cu-containing Dispersalloy amalgam was unaffected by polarization. When the diametral tensile strengths of polarized and unpolarized conventional amalgam and Dispersalloy specimens were compared (ADA Specification No. 1), no significant difference in strength was observed. These results indicate that the anodic corrosion of gamma2 phase network in the conventional amalgam fillings can be directly attributed to a reduction of tensile strength which would be manifested clinically as marginal breakdown. It appears also that the diametral tensile test is not sufficiently discriminating to allow for an in vitro simulation of clinical properties.

Copper↗
PubMed1977

The effect of temperature on the tensile strength and disintegration of paracetamol and oxytetracycline tablets.

The tensile strengths and disintegration times of paracetamol and oxytetracycline tablets at room temperature are higher when they have been prepared at high temperatures, e.g. 85 degrees, than at room temperature or below, e.g.--20 degrees. The activation energies of the two materials, 3 and 1 k cal mol-1 (13 and 4kJmol-1) respectively, were derived from plots of log tensile strength and log disintegration time versus the reciprocal of the absolute temperature. The results have been explained in terms of sintering theory and the formation of welded bonds between particles.

Acetaminophen↗
PubMed1992

Linear dimensional variability and tensile strengths of three solder index materials.

This study compared the linear dimensional change and tensile strengths of three indexing materials used for aligning joints to be soldered. Sixty rods 6 mm in diameter and 18 mm in length were made from base metal. The rods were divided into three groups of 10 pairs each, and a simulated solder gap was created between the rods in each pair. Ten simulated gaps were indexed with Duralay resin, 10 were indexed with Relate resin, and 10 were indexed with ZAPIT cyanoacrylate material. Measurements were made of each pair, before and after indexing, and the tensile strength of each indexed pair was measured and recorded. Linear measurements showed no significant difference between any of the groups. However, significant differences in tensile strength were found among all the materials tested.

Acrylic Resins↗
PubMed1979

Diametral tensile strength of twenty-three hardened commercial amalgams.

In view of the ever increasing number of high copper alloys, it was the aim of this study to investigate the tensile strength property of some of the new alloy systems. The factors alloy system and heat treatment were investigated in relation to the tensile strength. The factors alloy system as well as the heat treatment turned out to be significant. The study suggests that the introduction of "dispersion" alloys did not change the dental picture as to the property of the tensile strength. The selection of strength values in the range of 35-55 MN/m2 for the diametral tensile strength probably have no clinical relevancy as to the prevention of bulk fractures of amalgam restorations under oral conditions.

Copper↗
PubMed1978

Effects of temperature on the tensile strength of pharmaceutical powders.

Measurements have been made of the tensile strengths of fatty acids, lactose and of an oxtetracycline and a paracetamol tablet formulation at temperatures between -20 and +90 degrees. The measurements were made on compressed tablets and on consolidated beds of powders, using a diametral compression tester and a split plate tensile tester which had been designed to operate over this range of temperature. The tensile strengths of all the materials increase with temperature and values are given for the activation energies of bonding between particles.

Acetaminophen↗
PubMed1977

Tensile strength of wire-reinforced bone cement and twisted stainless-steel wire.

To assess the tensile strength of wire-reinforced bone cement as used for posterior spine fusion, standardized bone-cement specimens reinforced with stainless steel and Vitallium wires 0.5 and one millimeter in diameter were tested in tension. The results showed that tensile strength of bone cement was increased significantly by reinforcing it with metal wires, the increase in strength being proportional to the number of wires used. Even after failure of the cement, the reinforcing wires still carried an appreciable amount of load, thus avoiding the catastrophic failure of the cement alone. Specimens reinforced with Vitallium wires in general failed at higher loads than specimens reinforced with similar stainless-steel wires. Pull-out studies showed that a hook or a loop at the embedded end of straight wires significantly increased the load necessary to pull the wires out. The tensile strength of twisted stainless-steel wire composed of two 0.5-millimeter strands increased with the number of turns up to about eight turns per inch (2.54 centimeters) and then decreased.

Bone Cements↗
PubMed1992

[The effect of surface etching on tensile strength].

The aim of this study was to investigate the effect of different partial size of corundum used by sand blasting on the surface roughness and on the tensile strength. The conclusions of the authors were as follows: 1. The maximum values of tensile strength were measured when 200-250 microns corundum was used. 2. The values of the R(a) and Rmax were grown proportionally with the grain of corundum, but it was not resulted in the same increase of the tensile strength. 3. After the tensile test the residue of the bonding agent on one surface of the test-piece pairs, always remained significantly higher, than on the other, but this phenomenon cannot be explained by the differences between R(a) and Rmax within the test-piece pairs.

Acid Etching, Dental↗
PubMed1992

Compressive and diametral tensile strength of titanium-reinforced composites.

This article determines the compressive and diametral tensile strength of two titanium-reinforced composites (Bis-GMA-based), Ti-Core and Flexi-Flow cem with titanium and compares their strengths to dentin and commercially available core materials and cements. In addition scanning electron microscope (SEM) photographs were taken of Ti-Core and Flexi-Flow cem with titanium. Compressive and tensile loading was performed on a modified universal testing apparatus. Ti-Core and Flexi-Flow cem with titanium were measured to have compressive strengths of 41,132 and 41,876 psi and tensile strengths of 5219 and 4930 psi, respectively. Statistically (ANOVA, one-way analysis of variance), these titanium-reinforced composites are stronger in compressive and tensile strength than Ketac-Silver, Fleck's zinc cement, Durelon, Ketac-Cem, and GC Miracle Mix. Both titanium-reinforced composite materials approach the compressive and diametral tensile strengths of dentin (43,100 and 6000 psi). SEMs revealed that the titanium was uniformly and homogeneously interspersed within the resin matrix of the material.

Analysis of Variance↗
PubMed1976

Tensile strengths of twelve types of knot employed in surgery, using different suture materials.

When knotted loops of suture material were subjected to increasing tensile stress it was the knot that gave way in 710 of 720 experiments. The knot is thus the weakest point in the loop. A new code for describing knots useful in surgery has been worked out. The tensile strength of 12 different knots using twelve different suture materials with the dimension 3/0 (USP) was examined systematically. It was found that the efficiency of the knots varied depending upon the tensile strength of the material, 5% for the weakest and 99% for the strongest knot-material combination. Monofil and multifil steel threads were superior to other materials examined with regard to the knot strength. Chromic and plain catgut showed at least 50% of the tensile strength of the corresponding thread, irrespective of the type of knot. Silk was among the materials which gave the weakest knots. In principle, the more turns and throws the stronger the knot.

Chromium↗
PubMed1977

Tensile strength of fascia lata sutures following gamma radiation.

Gamma radiation (Co-60) is used to sterilize biological sutures. We wished to compare the effect of gamma-radiation in doses of 2.7 and 4.0 Mrads on the tensile strength of human fascia lata sutures obtained from the same cadaver. Five variables of tensile strength viz. Breaking Elongation, Breaking Load, Yield Point Load, Work of Rupture and Elastic Stiffness were determined for each suture. For Breaking Elongation the mean strength for the 4.0 Mrad dose was 3% less than for 2.7 Mrad dose (P less than 0.05); for Breaking Load 11% less (P less than 0.01); for Yield Point Load 9% less (P less than 0.02); for Work of Rupture 14% less (P less than 0.01); and for Elastic Stiffness 8% less (P less than 0.02). Irradiation with 4.0 Mrads, does not greatly change the tensile strength characteristics of fascia lata sutures.

Adult↗
PubMed1977

Ultimate tensile strength of gamma irradiated human scleral sutures.

Scleral sutures were prepared by hand from the equatorial region of 53 paired donor eyes. The weakening produced by two doses of gamma Co-60 radiation (2.7 and 4.0 Mrads) was compared using measurements of tensile strength; the strength of unirradiated scleral sutures was also measured, for comparison. The three variables of tensile strength, viz. Breaking Elongation, Breaking Load, and Work of Rupture was determined for each suture. As compared to unirradiated sutures, Breaking Elongation decreased on irradiation (P less than 0.01), but the two doses of irradiation were not statistically significant (P greater than 0.05); Breaking Load increased on irradiation (P less than 0.01), but the two doses of irradiation were again not significant (P greater than 0.05). Only 4.0 Mrads irradiated scleral sutures, as compared to unirradiated ones, showed a statistically significant reduction (P less than 0.01) for Work of Rupture. No definite relationships were found by regression analysis among the tensile strength variables and the independent variables of sex and various storage times for the 4.0 Mrad data. Work of Rupture showed a negative relationship to the age of donors, though the change with age was small.

Dose-Response Relationship, Radiation↗
PubMed1976

[The tensile strength of amalgam after 15 minutes].

The authors are mainly interested in the investigation of the tensile strength of a setting amalgam acquired after 15 minutes after the end of the trituration. Knowledge about this property is of interest because generally this moment corresponds with the time that a patient is asked to put the amalgam restoration into contact with the antagonist tooth. In two series of experiments eight commercial amalgam alloys, two different trituration techniques (hand and Silamat mixing machine) as well as two condensation techniques (hand and Bergendal vibrator) were tested. The reslts reveal that the tensile strengths of the different treatment combinations of amalgams prepared from Dispersalloy are significantly much higher than the minimum value of 2 MN/m2 which is required by the new stipulations of the A.D.A. specification n degrees 1. Some amalgams do not satisfy this requirement. Although the influence of the trituration technique as well as that of the condensation technique turns out to be significant, apparently the influence of the amalgam alloy is of much greater importance.

Dental Amalgam↗