Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Ceramics”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1977

[Comparative experimental investigations with bioglass (L. L. Hench), Al2O3-ceramic and Al2O3-ceramic coated with a mod. Bioglass. I. Results of experiments under non-loaded conditions (author's transl)].

This report deals with comparative results obtained with unloaded intra-osseous implants of bioglass (L. L. Hench), Al2O3-ceramic and Al2O3-ceramic coated with a mod. bioglass. Al2O3-ceramic and bone form a direct bony interface without fibrous tissue interposition, this resulting in a pure mechanic fixation of the implant through frictional forces of the surface roughed ceramic. Pure bioglass (45S5) and bone form a unique persisting direct interface by means of physico-chemical or biochemical phaenomena stabilizing the implant. Interface stability seams to be higher than the fatique strenth of the glass itself. This interface is developed as a consequence of solubility of some of the glass constituents within a surface layer of up to 200 microns, running parallel with a reduction of strength of this surface glass layer. The boronoxide containing bioglass, flame-sprayed onto Al2O3-ceramic samples seams to be less soluble and therefore seams to have lesser bonding capability to bone. The stability of the interface bioglass coating-Al2O3-ceramic was low.

Aluminum↗
PubMed1979

[Experimental study on an artificial hip joint made of Al2O3 ceramics (author's transl)].

For the purpose of developing the ceramic artificial hip joint, we carried out biological and mechanical experiments. Tiny blocks of polycrystalline ceramic were inserted into the femurs of rabbits. Also, ceramic powder was injected into the knee joints of rabbits. Biological reaction were examined after varying intervals. It was proved, as a result, that ceramics have good affinity with living tissue. As a next step, wedge-shaped test pieces were inserted into the distal end of the femurs of dogs and tensile tests were carried out to investigate the degree of fixation of ceramic with bone. The result was that ceramic test pieces showed firmer fixation than those of metal. In the hip joints of five dogs, ceramic total hip prostheses for dogs were implanted. The dogs were autopsied after varying intervals and investigated histopathologically and scanning electron microscopically. Fixation of the socket and the prosthesis with the bone was superior to those made of metal and, moreover, virtually no wearing had taken place. However, the socket or prosthetic stems in four dogs were observed damaged in some parts. From the above mentioned, it is evident that when making ceramic total hip prostheses, we have to select ceramics of good quality and thicken their weightconcentrated parts by a device of its own design or use partly metal components coated with ceramic.

Acetabulum↗
PubMed1976

[Studies on the application of apatite to dental materials. (I) --Apatite ceramics-- (author's transl)].

Apatite ceramics is composed of hydroxyapatite [Ca10(PO4)6(OH)2] sintered at high temperature. It is known that hydroxyapatite is the main component of bone and tooth minerals. There are two synthetic methods for the apatite powder. One is so called wet synthetic method: Synthesis by the reaction of Ca++ and PO4--- in the aqueous solution of approximately pH 7.0, the other is dry method: Synthesis by the solid state reaction at high temperature. The apatite powder stable below 1400 degrees C was prepared by the latter method in this work. After passing through a sieve, this powder was cold-pressed and then sintered at 1000 degrees C to 1300 degrees C in air. Biological apatite powders were also perpared as a reference. It was found that any apatite ceramics having porosity in the range of 5 to 50% could be obtained under the various sintering conditions. Compressive strength of these apatite ceramics increased with the reduction of the porosity, and those with porosity less than 20% were more than 100 kg/cm2. Vickers hardness was measured. This result showed the same tendency as that of compressibility. Hardness of the apatite ceramics with 90% relative density was almost the same or more as that of enamel. Solubility of the synthetic apatite powder in distilled water and aqueous solution of lactic acid (pH 4.0) was nearly the same as biological apatites. The dissolution rate decreased with the reduction of porosity of the ceramics. It was certified that hot pressing technique was extremely effective to obtain high density ceramics (more than 95% of density) and thus low parosity apatite ceramics. From the facts as described above, it is understood that sintered pure hydroxy-apatite is an excellent ceramics of high mechanical strength.

Apatites↗
PubMed1977

[Resorbable calcium phosphate ceramics under load (author's transl)].

Cylindrical implants with 45% by volume continuous open tubular pores were prepared from ceramic materials based on tricalcium and tetracalcium phosphate and used to replace 7 mm thick bone segments in the tibiae of dogs. The treated limbs of the experimental animals were fixed for 12 weeks, after which time the dogs were allowed to move freely so that the limbs were physiologically loaded. The histological examination showed that primary bone healing had taken place between the bone and the ceramic material. After 10 months the tricalcium-phosphate-based ceramic material was resorbed and replaced by bone tissue to a large extent. The ceramic material on the bases of tetracalcium phosphate on the other hand, had remained completely unchanged, and its pores were filled with lamellar bone tissue which was in direct contact with the implant without connective tissue. The bond between natural bone and implant was mechanically stable. The ceramic materials investigated were found to be tissue-compatible, and in our opinion they can be substituted for part of the bone transplants used today. Considering its varying strength properties, the tricalcium phosphate ceramic material can be used only in cases where no high stress is expected; the tetracalciumphosphate-based ceramic material, however, has a higher mechanical strength and can therefore be used also for larger permanent implants which have to bear high mechanical stress.

Animals↗
PubMed1978

[Release of toxic agents from ceramic utensils].

Under the influence of acidic agents, ceramic glazes and decorations for ceramics may release certain toxicants, especially lead and cadmium. Both elements are essential constituents of ceramic colours and glazes; their release to acidic foods is technologically unavoidable, but it may be minimized by the utilization of appropriate decoration agents and techniques. In most industrial countries, the release of toxicants from utensils is severely limited, the maximum permissible values and the methods of test and analysis being in part very different and not always in agreement with the demands and conditions of practice. The problems related to the release of toxicants from ceramic utensils are treated from the aspects of ceramics, test techniques, analytics, toxicology and food law, with special regard to the necessity for a well-balanced compromise between the justified hygienic demands of health protection and the actual technological possibilities. The endeavours of the ceramic industry of the GDF to produce ceramic utensils releasing as little toxicants as possible are outlined.

Cadmium Poisoning↗
PubMed1976

Effect of resorbable calcium aluminate ceramics on regulation of calcium and phosphorus in rats.

Ions released from resorbable ceramics could be toxic to the animal. Experiments were designed to study the effect of implanting three different weights of porous resorbable calcium aluminate ceramics (0.172, 0.332, and 0.504 g) in rats for a total duration of 300 days. Gross and microscopic examination of heart, liver, kidneys, trachea with thyroid, and muscle adjacent to the implant did not show any pathological changes. Calcium and inorganic phosphate content of bone, serum and urine were not affected by the implants. Urine hydroxyproline excretion did not change in the animals implanted with ceramics. Animals implanted with 0.332 g of ceramics had a significantly higher serum alkaline phosphatase activity than the control animals. Resorption of calcium and depositon of inorganic phosphates in the implanted ceramics suggested that ions were being exchanged with the body fluids. Implantation of 0.172 to 0.332 g porous resorbable calcium aluminate ceramic was not toxic to the animal.

Alkaline Phosphatase↗
PubMed1978

[Influence of the thickness of metal and porcelain upon metal-ceramics (author's transl)].

This paper deals with the strength of metal-ceramics and the influence of the thickness of metal and porcelain layer. The metal-ceramic specimens, 30 mm long and 10 mm wide of various each thickness, supported at each ends, were tested by bending to obtain the transverse strength. The thickness of metal layer was changed from 0.2 mm to 1.0 mm, while that of porcelain layer was changed from 0.5 mm to 1.3 mm respectively. Interaction of the thickness of metal or porcelain layer to the fixed total thickness was also investigated comparing with the results of the experiment in which the thickness of one side was constant. From the load-deflection diagram, the maximum work before breaking was surveyed and compared. Main results were as follows. 1) In case of the same total thickness of metal-ceramics, the thicker the metal layer, the greater the transverse strength, maximum work before breaking and maximum deflection. 2) When the metal thickness exceeded one half of the porcelain layer, the transverse strength increased in comparing with value of porcelain itself. 3) The maximum deflection of metal-ceramics by bending before breaking was approximately three or four times as great as that of simple porcelain. 4) The work of the metal-ceramics by bending before breaking was approximately two or three times as that of the simple porcelain. 5) It was imagined that the total strength of the metal-ceramics would be affected by the hardness of the constituent metal and boundary bonding strength.

Dental Alloys↗
PubMed1975

Morphological and biomechanical aspects of Al2O3 ceramic joint replacement. Experimental results and design considerations for human endoprostheses.

Four different acetabular replacement designs and 2 femoral head replacement designs made out of high density alumina ceramic have been tested in sheep with postoperative survival times of up to 11 months (Frialit 99: Al2O3 99.6%, MgO 0.4%). It can be concluded from these experiments that a cement free implantation technique with alumina requires a primary rigid fixation of the implant to bone, with the possibility for new bone growth along the ceramic and into grooves and macroscopic holes for further interdigitation. Three different solutions for the acetabular component can be recommended for human application. In addition, an all ceramic femoral prosthesis has been tested for bending strength in its neck region. Twenty prostheses have been factured, all of which showed values for bending strength far higher than the physiological neck fracture level (900 kp/cm2). The present state of development of all ceramic prostheses is discussed. Up to now, the development of fibrous tissue between the bone and the ceramic implant has caused reservations with human implantation. The direct definite anchorage problem has to be resolved first.

Acetabulum↗
PubMed1979

Leaching of lead from ceramics.

The amount of lead leached from various glazed ceramic was determined by extraction with 5% acetic acid for one hour at 85 degrees C. All commercial ceramic items, both domestic and imported, were below the FDA standard of 7 mg/liter lead in the extractant. On the other hand, almost 60% of the domestic homemade ceramic items exceeded FDA standards. Comparison with previous studies show significant reduction in lead leaching from commercial ceramic containers. However, homemade ceramic items continue to pose a potential hazard of excessive lead release.

Ceramics↗
PubMed1979

In vitro dissolution of Synthos ceramics in an acellular physiological environment.

"Synthos" (beta-tricalcium phosphate) implants in bone are resorbed and replaced with endogenous bone. This investigation was conducted to study by continuous flow and static system techniques, whether or not resorption of synthos occurs by passive dissolution at 37 degrees C. Calcium and phosphates were released in a time dependent manner from synthos in calcium and phosphate free Tris-Hcl buffer (pH 7.4). Scanning electron micrographs (SEM) of buffer exposed ceramics indicated breakdown of grain structure. In contrast, levels of human plasma calcium and phosphate were not altered by ceramics. Significant amounts of 32p were absorbed by the ceramics in the first hour and 45Ca in the second hour of exposure to plasma containing the radioactive isotopes. Exposure of ceramics to plasma did not alter the levels of plasm isotopes significantly for the remaining duration of the experiment. However, breakdown of grain structure was evident in SEM's of ceramics exposed to plasma. It appears that in an acellular physiological environment, dissolution of synthos is diffusion dependent and is limited to a localized surface exchange phenonmenon.

Blood↗
PubMed1979

Biocompatibility of apatite ceramics in mandibles.

Apatite ceramics composed of synthetic hydroxyapatite, Ca10(PO4)6(OH)2 were implanted in mandibles of adults dogs. The histological observations indicated that the apatite ceramic was closely contacted with newly formed bone tissue without any rejection phenomenon up to 2 weeks. An electron micrograph of non-decalcified ultra-thin section at 8 weeks showed that the apatite ceramic was directly bonded to newly formed bone and the mineralized bone tissue was grown into the micro pores of the ceramics independent on the pore size. It seemed that the outer surface of the apatite was exchanged by bone tissue. From these results it was considered that the apatite ceramic was a successful implant material in dental and surgical fields.

Animals↗
PubMed1979

Development of a ceramic surface replacement for the hip. An experimental Sialon model.

The objective of this study was to investigate the design and fixation advantages of Sialon ceramic surface replacements implanted without acrylic bone cement. The biocompatibility and friction and wear properties of Sialon ceramic were compared with more conventional prosthetic materials such as stainless steel and alumina. A functional load-bearing canine hip surface replacement model was established to test Sialon femoral cups designed for fixation by bone ingrowth. The results of the polyethylene wear tests on highly polished ceramic and stainless steel counterfaces were essentially similar. These laboratory data indicated that the in-vivo polyethylene wear performance on metal or ceramic prosthetic surfaces could be expected to be indistinguishable, i.e. the ceramic/polyethylene combination would not offer any improved wear resistance in-vivo. It was found possible to get bone ingrowth into the macrokeying areas of the ceramic femoral cups but not into the microporous surfaces due to the presence of a fibrous membrane lining their internal surfaces. The biocompatability specimens also appeared to be invested with a fibrous membrane. Further studies are under way to determine the relationship between reaming procedures, micro motion at the interfaces and Sialon biocompatibility.

Aluminum↗
PubMed1978

[Coating of metal implants with the bioactive glass ceramics Ceravital].

The bioactive glass ceramic Ceravital forms a physicochemical bonding with bone which is capable of withstanding stress caused by tension. This glass ceramic may already be put to clinical use as replacement for minor osseous parts. However, physical data are limited for maximum stress withstanding or gracile whole ceramic implants. In this study, metal cylinders from an alloy of CoCrMo are initially coated with a bio-compatible adhesive layer of enamel, approximately 0,2 to 0,3 mm thick. The adhesive strength of this kind of enamel amounts to about 120 to 140 kp/cm2. After the enamelling process, the glass ceramic is pressed into the enamel in granules at a particle size of 100 to 200 micrometer. As the first results show, this new process is suitable for the combination of metal implant stability and tissue compatibility of glass ceramic.

Animals↗
PubMed1977

Bonding mechanism evidence in a ceramic--nonprecious alloy system.

Bonding between porcelain and dental ceramic alloys is thought to be dependent upon the establishment of a continuous electron structure across the ceramic-metal interface (Pask, Proc. Porcelain Enamel Inst.,33,1,1971). Such a structure most likely results from the compatibility of metal ions at the metal surface saturated in an oxide form with the complex oxide structure of the ceramic matrix. Reaction zone compounds are expected to play a prominent role in the strength of the ceramic-metal bonds but thus far none have been detected or identified. The present study was centered on the determination of possible adherence zone compounds in four composite ceramic-metal couples examined by x-ray energy analysis. Elemental analysis of four couples revealed the presence of a predominant Al-Cr interaction resulting from the formation of an Al-Cr-O compound or mixed complex. The Cr ions were supplied by the Cr2O3 oxide layer at the metal surface and the Al was provided by the initial bonding-agent coating.

Aluminum↗