geoscience.net logo
+ Resolve Article
+ Follow Us
Follow on FacebookFollow on Facebook
Follow on TwitterFollow on Twitter

+ Translate
+ Subscribe to Site Feed
GeoScience Most Shared ContentMost Shared Content

Reinforcement of cores on porcelain jacket crowns. Influence of alumina powder properties on the cores


, : Reinforcement of cores on porcelain jacket crowns. Influence of alumina powder properties on the cores. Shika Gakuho. Dental Science Reports 89(4): 841-861

Various alumina particles were investigated for use as core reinforcement to strengthen aluminous-porcelain jacket crowns. The alumina particles were either spherical or nonspherical and were between 5.3 microns and 60 microns in size. Initially comparisons were made among such properties as particle-size distribution, apparent density, specific surface area, and flow. Then each alumina powder was mixed with feldspar at rates of from 10wt% to 70wt% at increments of 10wt%. Formed into columns, the powder was fired at 1350 degrees C for 5 minutes. The resulting feldspar-alumina composites were compared for shrinkage then cut and prepared into disc specimens. The disc-rupture test was employed to measure composite strengths. A scanning electron microscope was employed to observe alumina particles and composite cross sections. Results 1. Spherical alumina (average particle size 5.4 microns), spherical alumina (average particle size 28.9 microns), and nonspherical alumina (average particle size 58.0 microns) were higher in apparent density and flow rate but lower in specific surface area. 2. Feldspar-alumina composites shrank approximately 30%; shrinkage of 15-20% occurred only in composites involving spherical alumina (average particle size 5.4 microns). 3. Composites of feldspar and spherical alumina were observed to be stronger than those of feldspar and nonspherical alumina. Composites containing 50-60wt% (especially when the alumina particle size was 5.4 microns) were the sturdiest. 4. Increasing the amount of alumina proportionally increased composite strength. In composites containing nonspherical alumina, volume amount and strength were not always proportional. 5. Microscopic examination of composite cross sections showed uniform dispersion of spherical alumina but no dispersion of nonspherical alumina. In conclusion, spherical alumina (especially when average particle size is 5.4 microns) demonstrated the best powder properties as a reinforcing core material and therefore is most suitable for reinforcing the core of the porcelain jacket crown.

US$29.90

PMID: 2699675


Other references

Lloyd, Francis E., 1932: Is the door of Utricu-laria an irritable mechanism?. The physical properties of the door do not change during action and its action depends wholly on the pressure of the external medium (water) induced by the out-pumping capacity of the walls of the trap, first observed by Brocher, on the water-tigh...

Gorski, L.; Gronewold, T.; Kaiser, D., 2000: A sigma(54) activator protein necessary for spore differentiation within the fruiting body of Myxococcus xanthus. Insertion of an internal DNA fragment into the act1 gene, which encodes one of several sigma(54)-activator proteins in Myxococcus xanthus, produced a mutant defective in fruiting body development. While fruiting-body aggregation appears normal in...

Shulman, A.; Cade, G.; Dumble, L.; Laycock, G.M., 1972: The lethal action of 1,10-phenanthroline transition metal chelates and related compounds on dermatophytes and Candida albicans. C. albicans, Trichophyton mentagrophytes, T. rubrum, T. tonsurans, Epidermophyton floccosum and Microsporum canis were killed by the hydrochlorides, methiodides and fully coordinated transition metal chelates of 1,10-phenanthroline bases, sensitiv...

Rossmann, B., 1949: Loss of fat in food preparation. 2. Loss of fat in making potato pancakes. Grated potato, 150 g., and wheat flour, 10 g., were made into a dough, divided into 3, and fried in 15 g. fat. With less fat, results were not satisfactory. Butter, margarine, lard, oil or synthetic fat was used. Fat losses showed a smaller range...

Owen, D.H.; Agius, P.A.; Nair, A.; Perriman, D.M.; Smith, P.N.; Roberts, C.J., 2016: Factors predictive of patient outcome following total wrist arthrodesis. Total wrist arthrodesis (TWA) produces a spectrum of outcomes. We investigated this by reviewing 77 consecutive TWA performed for inflammatory and post-traumatic arthropathies, wrist instability and as a salvage procedure. All operations were perf...

Liu, J.Y., 1989: A new method for separating diffusion coefficient and surface emission coefficient. An analytical procedure was developed to separate the diffusion and surface emission coefficients in Newman's solution of the unsteady-state diffusion equation from a single lumber-drying curve. Previous methods required 2 to 4 drying curves...

Arnborg Lennart; Walker H.J.; Peippo Johan, 1967: Suspended load in the Colville River, Alaska, 1962. Geografiska Annaler: Pages 131-144. 1967.

Hoffmann, L., 1965: Models for prediction of yield on the basis of net energy and metabolisable energy. A polemical essay in which it is argued that the energy retained by an adult fattening animal can be computed with greater accuracy from an equation involving the "digestible" crude protein, crude fat, crude fibre and N-free extract of a...

Bennewitz, C.; Kuwert, T.; Han, J.; Ritt, P.; Hahn, D.; Thimister, W.; Hornegger, J.; Uder, M.; Schmidt, D., 2013: Computer-aided evaluation of the anatomical accuracy of hybrid SPECT/spiral-CT imaging of lesions localized in the neck and upper abdomen. The purpose of this study was to investigate the anatomical accuracy of hardware-based single-photon emission computed tomography/computed tomography (SPECT/CT) registration in the upper abdomen and neck. The database consisted of 90 patients refe...

Bacon, G.J.; Bachelard, E.P., 1979: Changes in growth substance levels associated with the conditioning of Pinus caribaea Mor. var. hondurensis B. & G. seedlings to water stress. Stock conditioning was effected by root-wrenching field-grown seedlings and by droughting and partial root-severance of phytotron-grown seedlings over a 4-month period. Chromatographed methanolic tissue extracts made at seedling age 6-10 months we...