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Results for “Compressive Strength”

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PubMed1990

The effect of dust-suppressant additives on the physical properties of an irreversible hydrocolloid.

The effects of dust-suppressant additives on certain physical properties of an irreversible hydrocolloid were studied in five test specimens formulated as follows: no additives (F0); 10% Duomeen cationic surfactant in 0.5% paraffin with 0.05% zinc stearate (F1); 10% Duomeen in 0.5% paraffin with 0.10% zinc stearate (F2); 20% Duomeen in 0.5% paraffin with 0.05% zinc stearate (F3); and 20% Duomeen in 0.5% paraffin with 0.10% zinc stearate (F4). The properties tested according to ADA specifications were mixing time, setting time, compressive strength, strain in compression, and permanent deformation under fixed strain. For each property, the variances between formulations were not significantly different (Levene p less than 0.05) whereas means were significantly different for stress (ANOVA p + 0.0001; Kruskal-Wallis p = 0.0019); strain (ANOVA p = 0.0003; Kruskal-Wallis p = 0.0228); deformation (ANOVA p = 0.0166; Kruskal-Wallis p = 0.0308). For the properties stress, strain, and permanent deformation under fixed strain, the paired differences of dust suppressants were established by using Duncan's multiple range test. Duomeen, instead of zinc stearate seems to be responsible for these effects.

Alginates↗

PubMedDate not supplied

Spherical alginate granules formulated for quick-release active subtilisin.

Novel attrition-resistant and spherical enzyme granules encapsulating active subtilisin were formed by emulsification of 2% alginate sol loaded with active enzyme, instantaneous gelation triggered through in situ release of Ca(2+) (internal gelation), particle separation, and finally acetone extractive drying. Granular subtilisin was highly active, readily dispersible, and mechanically robust. This technique serves as a new and attractive alternative to established enzyme granulation processes, such as fluid bed coating, extrusion followed by marumerization, drum granulation, or prilling, for use in industrial enzyme applications such as detergents, textile manufacturing, and food processing. The formulation and encapsulation conditions were optimized to maximize the resistance of the granule to compression and impact forces, consistent with enzyme release and particle dispersion in detergent solutions. Well characterized alginates, with specified guluronic/mannuronic acid (G/M) content and molecular weight, were used in the formulation. The characteristics of the resulting microspheres, including their size and distribution, morphology, shrinkage, compression resistance, impact strength, solubility and encapsulation yield, were examined. Spherical dry granules were formulated with a mean diameter of 500 microm with particle sizes ranging from 300 to 800 microm. Dry alginate granules were discrete, spherical, and glossy white and exhibited impact strength, compression resistance, and solubility difference dependent on composition. Reduced starch levels, high alginate concentration, low alginate molecular weight, and use of high guluronate alginates resulted in the lowest dust level and highest compression resistance. Subtilisin mass yields were approximately 50%, and specific activity yields ranged from 60% to 100%. A formulation consisting of 3% SG150 alginate, 10% starch, 10% TiO(2), and 1% CaCO(3) provided granules appropriate for use in detergent application.

Alginates↗

PubMed1976

Recent developments in alloys for dental amalgams: their properties and proper use.

Since the development more than ten years ago of a new type of amalgam alloy that will react with mercury without forming the unfavourable gamma2 (Sn7-8Hg) phase, several new alloy brands with a similar reaction pattern have been presented. This new generation of amalgam alloy is called non-gamma2 alloy as distinct from the conventional alloys. Three of the new alloys studied contain approximately three volume percent gamma2 and should be classified as modified concentional amalgams. The non-gamma2 amalgams may be characterized in the following way: (1) instead of gamma2 they contain a reaction product of copper and tin (Cu6Sn5), the so-called eta1 phase. (2) They are significantly more resistant to corrosion than the conventional amalgams but do in time produce sufficient solid corrosion products to seal the micro-fissures between filling and cavity walls. (3) When corroding, they do not release metallic mercury, and the solid corrosion products formed and precipitated on the free surface of the fillings seem relatively little resistant to the organic acids of the plaque. (4) Most of them have relatively low creep and tensile strength, but high compressive strength. (5) Clinically the non-gamma2 amalgams are remarkable for superior marginal integrity and, seemingly, also for improved persistence of surface lustre.

Copper↗

PubMed1989

[The production of denture by preform compression molding method. Part 2. Model material and fittability].

A preform compression molding method to make polysulfone denture was reported previously by paper. Properties of the mold, adaptability of the molded denture to master model and the movement of artificial teeth were examined. It was necessary to raise the temperature of the crystbalite-stone model above 270 degrees C to obtain stable expansion. Mold made using 22 wt%-colloidal silica showed strong compressive strength under the compression molding condition. Displacement of artificial teeth between wax denture and polysulfone denture was independent of the mold expansion, and the displacement was equal to that of heat-curing acrylic denture. Adaptability of the molded denture to the master model was associated with expansion of the model. Good adaptability was obtained under the expansion of the model, such as setting expansion about 0.30% and total expansion 1.05-1.10%, with about 0.2 mm average discrepancy.

Denture Design↗

PubMed1981

[Physical properties of adhesive 4-META resin cement (author's transl)].

4-Methacryloxyethyl trimellitate anhydride (4-META) had been reported to be a suitable monomer which promotes adhesiveness of PMMA rods with tooth substrates and metals. Previously an adhesive opaque resin which could eliminate mechanical retention devices from metal surface of crown and bridge metal frame was suggested. A new denture base resin, which is adhesive to metal denture plate, was also reported based on 4-META in MMA. We are going to publish a new application of 4-META to an adhesive dental cement in this paper. The physical properties of the new cement were measured: film thickness, 15 mu, tensile strength, 228 kg/cm2, compressive strength 920 kg/cm2, transvers strength , 530 kg/cm2, water sorption, 1.97 mg/cm2. Tensile adhesive strength of the cement was higher than 100 kg/cm2 between PMMA rods and dentine, enamel, dental alloys, and the stability was acceptable.

Acrylates↗

PubMed2004

Nonstoichiometric hydroxyapatite granules for orthopaedic applications.

A new method for the preparation of nonstoichiometric hydroxyapatite (HA) "dense" and porous granules, round in form and up to 8 mm in sizes designed for application in orthopaedic surgery has been developed. The "dense" granules' porosity was up to 32% and they only contained micropores. They differed from that kind of granules by increased values of compression strength (up to 48 MPa). The porous granules contained a system of interconnected micro- and macropores. The porosity value (up to 70%) and the porosity structure were similar to those in the mineral framework of a spongy bone. The compression strength of the porous granules (up to 25 MPa) was high enough for various kinds of application. Granules of both sorts were used in performing 42 operations on the locomotor system. Depending upon localization and supposed level of the injured area loading, "dense" or porous granules were used. The postoperative observations (up to four years in length) have attested to the high quality of the granules.

Adolescent↗

PubMed2006

Cancellous bone from porous Ti6Al4V by multiple coating technique.

A highly porous Ti6Al4V with interconnected porous structure has been developed in our previous study. By using a so-called "Multiple coating" technique, the porous Ti6Al4V can be tailored to resemble cancellous bone in terms of porous structure and mechanical properties. A thin layer of Ti6Al4V slurry was coated on the struts of base porous Ti6Al4V to improve the pore structure. After two additional coating, pore sizes ranged from 100 microm to 700 microm, and the porosity was decreased from approximately 90% to approximately 75%, while the compressive strength was increased from 10.3 +/- 3.3 MPa to 59.4 +/- 20.3 MPa and the Young's modulus increased from 0.8 +/- 0.3 GPa to 1.8 +/- 0.3 GPa. The pore size and porosity are similar to that of cancellous bone, meanwhile the compressive strength is higher than that of cancellous bone, and the Young's modulus is between that of cancellous bone and cortical bone. Porosity, pore size and mechanical properties can be controlled by the parameters in such multiple coating processes. Therefore the porous Ti6Al4V with the characteristics of cancellous bone is expected to be a promising biomaterial for biomedical applications.

Alloys↗

PubMed2004

Foamed lightweight materials made from mixed scrap metal waste powder and sewage sludge ash.

The porous properties and pozzolanic effects of sewage sludge ash (SSA) make it possible to produce lightweight materials. This study explored the effects of different metallic foaming agents, made from waste aluminium products, on the foaming behaviours and engineering characteristics, as well as the microstructure of sewage sludge ash foamed lightweight materials. The results indicated that aluminium powder and mixed scrap metal waste powder possessed similar chemical compositions. After proper pre-treatment, waste aluminium products proved to be ideal substitutes for metallic foaming agents. Increasing the amount of mixed scrap metal waste by 10-15% compared with aluminium powder would produce a similar foaming ratio and compressive strength. The reaction of the metallic foaming agents mainly produced pores larger than 10 microm, different from the hydration reaction of cement that produced pores smaller than 1 microm mostly. To meet the requirements of the lightweight materials characteristics and the compressive strength, the amount of SSA could be up to 60-80% of the total solids. An adequate amount of aluminium powder is 0.5-0.9% of the total solids. Increasing the fineness of the mixed scrap metal waste powder could effectively reduce the amount required and improve the foaming ratio.

Aluminum↗

PubMed2007

Ion leaching of a glass-ionomer glass: an empirical model and effects on setting characteristics and strength.

The release of ions from a glass-ionomer glass, which in the polyacid matrix effects the cross-linking and setting of a cement, can be modelled and initiated by acid-treatment in a dilute acid. This study examined the effect of time of acetic acid leaching on the working time, setting time, and strength of a model GIC. A reactive fluoride glass was immersed in hot acetic acid for 0 (control), 5, 15, 35, 65, 95 and 125 min, filtered and dried. The glass was mixed with an experimental GI liquid in a capsule system and the mixed pastes assessed for working and initial setting time. Compressive strength testing was undertaken according to ISO9917:2003. Immersion time had a significant effect on both working and setting time of the resultant pastes only up to 65 min of immersion, and corresponded with a thin-film ion diffusion model. Compressive strength did not vary significantly with immersion time. The glass-ionomer setting reaction can be conveniently retarded by immersion of the powder in acetic acid, without affecting strength. A reactivity model was developed, whereby the effects of various changes to the leaching process may be usefully examined.

Acetic Acid↗

PubMed2005

Modulation of porosity in apatitic cements by the use of alpha-tricalcium phosphate-calcium sulphate dihydrate mixtures.

Calcium phosphate bone cements are injectable biomaterials that are being used in dental and orthopaedic applications through minimally invasive surgery techniques. Nowadays, apatitic bone cements based on alpha-tricalcium phosphate (alpha-TCP) are of special interest due to their self-setting behaviour when mixed with an aqueous liquid phase. In this study, a new method to improve osteointegration of alpha-TCP-based cements is presented. This method consists in the modification of the cement's powder phase with different amounts of calcium sulphate dihydrate (CSD). The resulting hardening properties of the new biphasic cements are a combination between the progressive hardening due to the main alpha-TCP reactant and the progressive dissolution of the CSD phase, which render a porous material. It was observed that the maximum compressive strength of Biocement-H (45 MPa) decreased as the amount of CSD increased in the cement powder mixture ( approximately 30 MPa for 25 wt% of CSD). It was also observed that after complete dissolution of the CSD phase a porous apatitic structure appears with a mechanical compressive strength suitable for cancellous bone applications (10 MPa).

Apatites↗

PubMed2006

Influence of powder particle size distribution on complex viscosity and other properties of acrylic bone cement for vertebroplasty and kyphoplasty.

For use in vertebroplasty and kyphoplasty, an acrylic bone cement should possess many characteristics, such as high radiopacity, low and constant viscosity during its application, low value of the maximum temperature reached during the polymerization process (T(max)), a setting time (t(set)) that is neither too low nor too high, and high compressive strength. The objective of this study was to investigate the influence of the powder particle distribution on various properties of one acrylic bone cement; namely, residual monomer content, T(max), t(set), complex viscosity, storage and loss moduli, injectability, and quasi-static compressive strength and modulus. It was found that the formulations that possessed the most suitable complex viscosity-versus-mixing time characteristics are those in which the ratio of the large poly(methyl methacrylate) beads (of mean diameter 118.4 microm) to the small ones (of mean diameter 69.7 microm) was at least 90% w/w. For these formulations, the values of the other properties determined were acceptable.

Biocompatible Materials↗

PubMed1998

Changes on storage of polyacid-modified composite resins.

Two polyacid-modified composite resins, Dyract and Compoglass, have been studied for water-uptake on storage in three aqueous media, namely pure water, 0.9% NaCl and 1 M NaCl at 37 degrees C, and the results compared with those of a conventional composite resin, Pekafill. The equilibrium water-uptake of Dyract and Compoglass varied depending on time of cure and ionic strength of the storage medium. This latter finding contrasted with that for Pekafill, where equilibrium water content showed almost no variation with ionic strength of the storage medium. Uptake of water was always greater in Dyract and Compoglass than in Pekafill, reflecting the role of water in promoting the later neutralization reaction in these materials and its further role in hydrating the ionic products of that reaction. Despite this and other evidence of neutralization, specimens of Dyract and Compoglass stored in wet conditions (0.9% NaCl) showed no change in compressive strength on storage from 24 h to 30 days, a result similar to that reported previously for Dyract alone for flexural strength for times up to 1 year. By contrast, specimens of Dyract and Compoglass stored in dry air at 37 degrees C, and therefore unable to undergo any neutralization, showed an increase in compressive strength of between 40 and 70 MPa by 30 days that was significant at P < 0.01.

Air↗

PubMedDate not supplied

Mechanical properties of compomer restorative materials.

The purpose of this study was to measure the compressive strength, flexural strength, microhardness, and surface roughness of three compomers (Compoglass, Dyract, and Hytac) and compare the values to the ones obtained for a resin-modified glass-ionomer cement (Vitremer) and a resin composite (Z100). All materials were handled according to the manufacturers' instructions. There was a significant difference (P < 0.01) among Vitremer, Hytac and Z100 composite with regard to yield strength. Vitremer values were lower than for Hytac, which were lower than for Z100. The yield strength values for Compoglass and Dyract were significantly lower than for Hytac and Z100 composite and significantly higher than for Vitremer (P < 0.01). There was no significant difference in the strain at yield among Vitremer, Hytac, and Z100, but their values were significantly higher than for Compoglass and Dyract (P < 0.01). The flexural strength data displayed a significant difference between Vitremer and Hytac (P < 0.05). Z100 was significantly stronger than the other products tested. The values of strain at break for Vitremer, Hytac, and Z100 were significantly lower than for Compoglass and Dyract (P < 0.01). The compressive strength results showed significantly higher values for Dyract, Compoglass, and Hytac than for Vitremer (P < 0.01). Z100 displayed higher values than the other products tested (P < 0.01). Hytac strength was significantly higher than for Dyract (P < 0.01). The microhardness of Compoglass and Dyract was not significantly different (P < 0.05). Hytac displayed microhardness values higher than for Vitremer, Compoglass, and Dyract (P < 0.01). However, all products tested showed values significantly lower than for Z100 (P < 0.01). The surface roughness values for Compoglass, Dyract, Hytac, and Z100 were not significantly different. Vitremer displayed a significantly higher value than Dyract, Hytac, and Z100 (P < 0.05).

Analysis of Variance↗

PubMed2001

Fibrous tissue armoring increases the mechanical strength of an impacted bone graft.

Impacted, morselized bone allografts are used with good clinical results in revision of hip prostheses with loosening and osteolysis. The impacted bone graft appears radiographically to remodel, but histological analyses have shown a heterogeneous picture with a mixture of living and dead bone. Thus, complete remodeling of the graft may be neither a prerequisite nor a cause of the good clinical results. The present study concerns the mechanical effect of the mere armoring of the bone graft by ingrowing fibrous tissue. We compared the compression strength of freshly-impacted grafts to grafts that had been inserted into a bone chamber and thus were penetrated by fibrous tissue growing in between the graft trabeculae. The compressive strength was doubled after 4 weeks of fibrous ingrowth. We conclude that the mechanical properties of an impacted graft are enhanced by armoring with ingrowing fibrous tissue. Strengthening of the parts of the impacted grafts which have not yet remodeled, would be clinically relevant for the outcome of the operation, since these parts are at high stress during the whole remodeling period. Complete osseous remodeling may not be necessary to obtain a good clinical result with a morselized impacted graft.

Animals↗

PubMed2005

Effects of hydrogen peroxide cleaning procedures on bone graft osteoinductivity and mechanical properties.

Bone allografts are frequently used during orthopaedic trauma cases or other reconstructive procedures. Most allografts are processed and cleaned before use. Our goals were to determine if an improved cleaning procedure compromises the strength or osteoinductivity of a graft. We compared our improved cleaning procedure to our standard cleaning procedure on cortical bone allograft. The cleaning procedures are generally composed of a series of chemical steps with nonionic detergents, hydrogen peroxide, and alcohol under time and temperature control, subjected to ultrasonic agitation. We tested the compressive strength, impact strength, and shear strength following the standard and improved cleaning procedures. Osteoinductivity was tested in 4 groups, using the improved cleaning procedure with four different hydrogen peroxide cleaning times: 0, 1, 3, and 5 h. Osteoinductivity was evaluated in vivo, using a 28-day implant in the hamstring muscle of an athymic, nude mouse. Results demonstrated that osteoinductivity is maintained with cleaning in hydrogen peroxide for up to 1 h, and that compressive strength, impact strength, and shear strength were all unaffected by the improved cleaning procedure. The improved cleaning procedure therefore did not compromise the strength or osteoinductivity of cortical bone allografts in comparison to the standard procedure.

Adult↗

PubMed2005

Evaluation of different bonded investments for dental titanium casting.

The properties of several different investments were investigated including phosphate bonded, magnesia bonded, and alumina cement investments. Measurements included the setting expansion, thermal expansion, and compressive strength of investments, as well as the tensile strength, elongation, Vickers hardness (VHN) and surface roughness of titanium castings. For phosphate bonded investment, the setting expansion after being mixed with its own mixing solution was 2.10%, which was larger than the other investments; the thermal expansion was -0.25% at 200 degrees C, the compressive strength 14 and 5 MPa after heating. For titanium cast in phosphate bonded investment, the hardness on its top surface was 655 Hv, the tensile strength was 379 MPa, the elongation was 19.4%, and the surface roughness was 2.29 microm. Although the thermal expansion of phosphate bonded investment is small, the setting expansion is large enough to compensate for the shrinkage of titanium castings. As its thermal expansion at T > or = 600 degrees C was constant and its heating-cooling cycle was almost reversible, these two properties can reduce the thermal shock and thus avoid cracking of the investment.

Aluminum Oxide↗

PubMed2006

Effect of spherical silica filler addition on immediate interfacial gap-formation in Class V cavity and mechanical properties of resin-modified glass-ionomer cement.

The aim of this study was to investigate how the addition of silanized spherical silica filler (SF) would influence the formation of summed, immediate interfacial gaps in Class V tooth cavities. Resin-modified glass-ionomer cement (RMGIC) is usually used for Class V restorations. As such, the following aspects of RMGIC were examined in correlation with summed interfacial gaps in the tooth cavity: setting shrinkage of cement in the Teflon mold, as well as mechanical properties in terms of compressive strength, diametral tensile strength, and flexural strength. Spherical silica filler was added to the RMGIC powder (Fuji II LC EM). For comparison purpose, untreated spherical silica filler (UF) was added too. When compared with the control (i.e., original RMGIC mixed with manufacturer-recommended powder/liquid ratio), the addition of SF significantly decreased the formation of summed interfacial gaps in Class V cavities in the immediate condition. In particular, addition of 10 wt% SF increased the compressive strength by 56%, while diametral tensile strength was increased by 28% and flexural strength by 26%.

Analysis of Variance↗

PubMed2003

Daily treatment with parathyroid hormone is associated with an increase in vertebral cross-sectional area in postmenopausal women with glucocorticoid-induced osteoporosis.

Daily treatment with hPTH (1-34) is associated with a significant increase in bone formation which results in large gains in lumbar spine bone mass. However, bone formation is known to occur on trabecular, endocortical and periosteal surfaces. The purpose of this study was to determine whether daily treatment with hPTH (1-34) for 1 year was associated with a change in vertebral cross-sectional area, or vertebral size, as measured by serial quantitative computed tomography scans. Fifty-one postmenopausal women treated chronically with both glucocorticoids and hormone replacement therapy (HRT) were randomized to either daily hPTH (1-34) for 1 year and HRT or to a control group treated with only HRT. Measurements of bone density of the spine were obtained every 6 months by dual-energy X-ray absorptiometry (DXA) and annually by QCT of the L1 and L2 vertebrae. Vertebral cross-sectional area (VCSA) was obtained from the QCT scans. In addition, we estimated the vertebral compressive strength (VSFOM, g(2)/cm(4) = trabecular BMD(2) x VCSA). After 1 year of hPTH (1-34) treatment, VCSA increased 4.8% (p < 0.001), and 1 year after treatment was discontinued VCSA was still 2.6% higher than the baseline value (p < 0.05). The control group had no change in VCSA. In addition, estimated vertebral compressive strength increased more than 200% over baseline levels in the hPTH (1-34) treatment group and no change was observed in the control group. In summary, daily treatment with hPTH (1-34) for 1 year increased vertebral size as measured by VCSA and this increase was maintained after hPTH (1-34) was discontinued. Since vertebral fracture risk is related to both bone size and bone mass, we cautiously speculate that the increase in vertebral size associated with hPTH (1-34) treatment is at least partially responsible for increased vertebral bone strength and reduction of fracture risk associated with this therapy in postmenopausal osteoporosis.

Absorptiometry, Photon↗