PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “DENTAL PORCELAIN”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 73 records · Page 4Linked to original sources
PubMed1997

Optimum particle size distribution for reduced sintering shrinkage of a dental porcelain.

OBJECTIVES: The purpose of this investigation was to develop a systematic method for obtaining an optimum particle size distribution for a given dental porcelain and compaction method that had a low sintering shrinkage. METHODS: Particles of coarse, medium and fine size were obtained from a commercial dental porcelain using a sedimentation method. Particle sizes were chosen so that the smaller particles would fit into the interstices between the next larger size. The different-sized powders were mixed in various proportions and compacted into a cylindrical mold. The specimens were fired and their linear firing shrinkages determined. An equation was developed to predict optimum proportions. The shrinkage of these mixed powders was compared to the shrinkage of the component powders, to the as-received commercial porcelain, and to predictions based on theoretical equations. These comparisons were statistically analyzed using analysis of variance (ANOVA) and Fisher's Protected Least Significant Differences (PLSD). RESULTS: Mixing specific proporations of different-sized particles significantly reduced sintering shrinkage (p = 0.01) for all mixtures except for one trimodal mixture having the smallest particles. These reductions in shrinkage were obtained for the proportions predicted by the developed equation. Sintering shrinkages for predicted proportions of a three-component mixture and two two-component mixtures were significantly less than that of the original powder (p = 0.01). SIGNIFICANCE: A systematic method was developed for producing dental frits with low firing shrinkage. Mixing of different-sized particles produced frits with lower sintering shrinkage. The optimum proportions of the sized particles were given by an equation. The results of this study suggest that optimum particle size distributions for frits are dependent upon compaction methods.

Aluminum Silicates↗
PubMed1993

Prediction of the service life of dental porcelains by the measurements of post-indentation slow crack growth.

Statistical fatigue life for body dental porcelains, cooled in a furnace and in air, was predicted from measurements of post-indentation slow growth of radial cracks in water and in air. Cracks were induced in the surfaces of porcelain discs by a Vickers indenter at an applied load of 9.8 N. Crack lengths were measured at various times over a period of 5 months to calculate the stress corrosion susceptibility coefficient, n. Lifetime under service stress was estimated from the measured value of n. The ratios of service stress to fracture strength were calculated as 0.47 and 0.69, respectively, for glassy and feldspathic porcelains which were cooled in a furnace and aged in water. The corresponding ratios for tempered (cooled in air) specimens were 0.58 and 0.67, respectively. These were estimated values when service life exceeds 10 years. The results suggest that the air cooling process can effectively increase the service life of glassy porcelains, but, for feldspathic porcelain it is less effective.

Corrosion↗
PubMed1992

The influence of surface conditions and silane agents on the bond of resin to dental porcelain.

The influence of porcelain surface condition and the application of silane agents on the adhesion between resin and dental porcelain were investigated. The experimental variables included three porcelain surface preparations, as polished, etched with phosphoric acid, or etched with hydrofluoric acid and three kinds of commercially available silane coupling agents. The shear bond strength between the light-cured composite and the dental porcelain was measured after one-day immersion in 37 degrees C water. Samples without the silane agent application were also tested as controls. Without the silane agent, hydrofluoric acid-etched specimens had a higher bond strength than polished or phosphoric acid-etched specimens. The combination of hydrofluoric acid-etching and an application of Cosmotech Porcelain Primer increased the bond strengths more than that of phosphoric acid-etching. With the application of Laminabond Porcelain Primer or Optec Silane Coupling Agent, high bond strengths were obtained regardless of the porcelain surface condition. Therefore, it seems the chemical reactions between the porcelain surface and silane agents were responsible for the high shear bond strengths.

Acid Etching, Dental↗
PubMed1994

A comparison of the color stability of conventional and titanium dental porcelain.

Simulation of naturally appearing enamel in fixed prosthodontics is best achieved with porcelain. This study investigated the color stability of two different dental porcelains, Ceramco and Procera, after they were exposed to 900 hours of accelerated aging. Twenty titanium plates provided the substrate to which the Procera porcelain samples in shades A3, A3.5, C3, and D3 were fired, five in each shade. An equal number of metal-ceramic alloy (Olympia) plates were cast to the same dimensions to form the 20 substrates to which Ceramco porcelain was fired. The four shades of porcelain were again added to each of the samples. Commission International de l'Eclairage L a b readings were recorded with a Minolta Chroma Meter II before and after exposure to 900 hours of accelerated aging simulation. After the aging process the color differences between the pretest and posttest condition were calculated. Although statistical comparisons demonstrated a difference in color change (p < or = 0.05) between Ceramco and Procera porcelain in three of the shades tested, critical remarks of color refer to both types having "slight" color change. In terms of color stability, neither porcelain had "noticeable" changes after 900 hours of accelerated aging.

Color↗
PubMed1975

Evaluation of the physical properties of crown dental porcelain and the effect of newly developed anti-binding additive.

A colloidal silica-based substitute for the water added to dental porcelain has been developed which restricts rounding on firing and gives greater and indefinitely prolonged unfired biscuit strength. In conjunction with product evaluation, it has been found that both the modulus of rupture and the diametrical tensile strength of dental porcelains can be measured with a high degree of precision.

Borates↗
PubMed2002

Microstructure effect on the properties of a commercial low-fusing dental porcelain.

The aim of this study was to investigate the effect of firing cycle on a dental porcelain microstructure in order to correlate microstructure changes with mechanical and thermal properties. A commercial low-fusing dental porcelain powder (Omega 900, Vita) was investigated for this purpose. The powder was treated at different temperatures in the range 750-1000 degrees C. The fired samples were characterized in terms of their morphology and microstructure, and their mechanical and thermal properties were evaluated. The results showed that firing temperature affects porcelain microstructure influencing significantly in this way both the mechanical properties and the thermal expansion coefficient of the fired objects. Firing at 800 degrees C led to a homogeneous structure. After treatment at this temperature, the leucite crystals exhibit their maximum concentration and they are well dispersed into the glassy phase. As a consequence the optimum mechanical strength and the maximum thermal expansion coefficient are observed in these samples.

Journal Article↗
PubMed2002

Opalescence of dental porcelain enamels.

OBJECTIVE: The objective of this study was to compare the microstructures of teeth, natural opals, and opal dental enamel porcelains to examine the mechanisms that cause opalescence. METHOD AND MATERIALS: Four dental porcelains, a natural opal mineral, and a human tooth were examined. Replicas were assessed in transmission electron microscopy for features that would cause opalescence. Enamel dental porcelains denoted as "light" were selected for the study. X-ray diffraction and color analyses of the porcelains were also performed. RESULTS: All the materials were opalescent, to varying degrees. The porcelains with fewer microscopic features were less opalescent. The presence of dispersed particles or a phase-separated glass was found to cause opalescence in dental porcelains. CONCLUSION: A phase-separated glass in one enamel porcelain best resembled the microstructure of natural opal mineral and teeth, and this was the most "opalescent" material.

Algorithms↗
PubMed1999

Fracture toughness (KIc) of a dental porcelain determined by fractographic analysis.

OBJECTIVES: Fractographic analysis of indentation cracks is performed following flexure testing as part of the ASTM (1999) standard for fracture toughness, KIc, determination in advanced ceramics. This method depends on the conduciveness of the material towards fractographic interpretation. The purpose of this study was to evaluate the use of fractography in fracture toughness methods with a feldspathic dental porcelain, in which KIc was measured fractographically as well as numerically using two controlled-flaw beam bending techniques. METHODS: The following methods for KIc determination were applied to a dental porcelain containing a leucite volume fraction of 15-20%: (1) surface crack in flexure (SCF) (dependent upon fractographic analysis); and (2) indentation strength (IS) at indentation loads of 9.8 and 19.6 N (applying both standard numeric calculations and fractographic analysis). The testing environments were (1) ambient air (IS and SCF) and (2) flowing dry nitrogen (SCF). RESULTS: No significant differences were found between numeric and fractographic KIc values for the IS technique at both indentation loads (9.8 and 19.6 N) in ambient air, although KIc values were sensitive to indentation load. Due to the presence of residual stresses, stable crack extension was observed fractographically in all IS specimens, as evidenced by differences between initial (ainitial) and critical (acritical) crack dimensions. For the SCF method, there was a significant difference in toughness between specimens tested in air versus dry nitrogen, however no fractographic evidence for chemically assisted slow crack growth (SCG) was observed. SIGNIFICANCE: The SCF method as described by the ASTM standard was applicable to the feldspathic porcelain and produced very comparable results with the numeric toughness calculations of the IS procedure. However, fractographic analysis of the surface crack was somewhat difficult for this glassy ceramic compared with polycrystalline ceramics. Knowledge about stable crack extension or slow crack growth and its fractographic appearance is essential when estimating the toughness from examination of flaw dimensions on fractured surfaces since large calculation errors may occur if these effects are not taken into account.

Aluminum Silicates↗
PubMed2006

Physical properties and microstructural characterization of dental porcelains mixed with distilled water and modeling liquid.

OBJECTIVE: The aim of this study was to microstructurally characterize and to make comparisons of the physical properties of sintered dental porcelains prepared by mixing with distilled water and with their modeling liquid. METHODS: Six commercial porcelain powders: IPS Classic (Ivoclar Vivadent AG, Schaan, Liechtenstein), IPS d.SIGN (Ivoclar Vivadent AG), IPS InLine (Ivoclar Vivadent AG), Vita VMK95 (Vita Zahnfabrik, Bad Sackingen, Germany), Vita OMEGA 900 (Vita) and Ceramco III (Ceramco-Dentsply, Burlington, NJ, USA) were used as starting powders. Following particle size and BET analyses of starting powders, each porcelain powder was mixed with distilled water and with its own modeling liquid. Disc specimens were sintered in accordance with each manufacturer's instructions. Specimens were characterized using X-ray diffraction (XRD), optical microscopy and SEM analysis and their physical properties such as bulk density, microhardness and biaxial flexural strength were determined. RESULTS: The sintered dental porcelains premixed with modeling liquid had density, biaxial flexural strength and microhardness values slightly higher than those premixed with distilled water. Mixing with distilled water and modeling liquid caused statistically significant differences between the density values of Vita VMK 95 and microhardness values of IPS d.SIGN and IPS InLine. Characterization investigations (XRD and SEM) revealed the coexistence of the tetragonal leucite (1-3 microm) and hexagonal fluorapatite crystals (0.4-1.2 microm) in a feldspathic glassy matrix in the microstructure of IPS d.SIGN and only leucite crystals (3-6 microm) in the microstructures of other porcelains. SIGNIFICANCE: Mixing the porcelain powders with distilled water or modeling liquid prior to sintering has no effect on the resultant sintered crystalline microstructure. On the other hand, significant differences exist between the physical properties of some porcelains.

Aluminum Silicates↗
PubMed1981

A technique for the production of standard test specimens of aluminous dental porcelain.

A technique has been developed for the preparation of test bars of the different types of aluminous porcelains using the standard laboratory procedures for the preparation of aluminous porcelain jacket crowns. Up to now the investigation of the properties of dental porcelain has been conducted using test specimens produced either by vibration of a slurry of porcelain powder without platinum foil or by grinding from the solid brock. These techniques are far removed from the methods used for the production of porcelain restorations in the laboratory. This might lead to a variation in the results achieved by testing porcelain jacket crowns on the one hand and test specimens on the other.

Aluminum↗
PubMed1989

Transient and residual stresses in dental porcelains as affected by cooling rates.

The development of either transient or residual stress in a slab of dental porcelain during cooling was simulated by use of a super-computer. The temperature dependences of the elastic modulus, the thermal expansion coefficient, and the shear viscosity, and the cooling rate dependence of the glass transition temperature, Tg, were considered in this calculation. Internal stress and viscoelastic creep were computed for several cooling rates. Calculated results display stress profiles which agree reasonably well with reported measured profiles in quenched, tempered glasses. The calculated residual surface stress, sigma, could be fit by the following empirical formula, sigma = kl2(q/q0)n, q is the cooling rate, q0 is a reference cooling rate and l is the half-thickness of the porcelain. The method by which residual stress develops is also discussed. This discussion suggests a method for strengthening of the porcelain by the development of high-compressive residual stress on the surface.

Computer Simulation↗
PubMed1990

[Adherence of porcelain and metal after firing in H2. 1. Dental porcelain and nickel-chromium alloy].

The materials for porcelain fusing used in this study were nickel-chromium alloy and ceramco opaque porcelain. The opaque porcelain was fused on the metal surface firing in routine method and in H2. And, the shearing test, X-ray diffraction and quantative analysis of O2 were done. The strengths of the specimens firing in H2 were larger than those of ones firing in routine method. We found that SnO2 of porcelain changed into Sn after firing in H2.

Adhesiveness↗
PubMedDate not supplied

Cyclic mechanical fatigue of a feldspathic dental porcelain.

A blunt-indentation fracture mechanics technique was used to investigate the response of a feldspathic dental porcelain to cyclic mechanical fatigue. The indentation stress-strain curve was determined first, which showed the critical pressure necessary for crack initiation. This research also demonstrated that pressures too small to cause immediate catastrophic failure can still cause irreversible damage. A second series of fatigue experiments, using pressure parameters chosen from the first project investigated strength loss. These experiments showed that the porcelain was susceptible to cyclic mechanical fatigue, and that cyclic mechanical fatigue is different from quasistatic fatigue. Strength loss curves indicated that cyclic mechanical fatigue damage is cumulative and permitted quantification of the severity of accumulated damage.

Aluminum Silicates↗
PubMed1988

[Analysis of the oxides and their adherence in precious, high palladium and non precious porcelain dental alloys].

The interfacial oxides formed during the oxidation stage of porcelain dental alloys are of primary importance. The purpose of this study was to identify the type of the oxides in three commercial alloys and to evaluate their adherence with the underlying alloy before and after porcelain application. X-ray diffraction analysis revealed the presence of PdO, Fe2O3, FeO, InO, In2O3 (precious alloy), Ga2O3, GaO, PdO, CuO, SnO2 (Hi-Pd) and NiO, Gr2O3, SiO2, MoO2, TiO2, Al2O3 (non precious) in the oxide layers removed from each alloy respectively with a 10% Br solution in methanol. The highest values of tensile strength were obtained from the non-precious alloy oxides which were further enhanced after porcelain fusion. The application of porcelain does not seem to influence metal ceramic bonding.

Adhesiveness↗
PubMed1980

[Non-destructive neutron activation analysis of dental porcelain powders (author's transl)].

Determination of 15 elements in the dental porcelain powders (Vita VMK 68) marketed in Japan was done by means of non-destructive neutron activation analysis. The potassium and sodium contents showed less variations from powder to powder, and the uranium contents varied from a few ppm to 1090 ppm in a wide range. The high contents of uranium (345--1090 ppm) were detected in the powders of Enamel, Dentin, Effect, Color and Gum which were used for the superficial parts of a porcelain crown, while the low contents of uranium (1.6--2.7 ppm) were detected in those of Opaque and Translucent which were used for the core part and the top of the crown. Cerium and samarium were also detected in each powder in the amounts similar to those of uranium. The main radionuclides present in the porcelain powders were 238U, 235U, 234U, 234mPa, 234Th, 231Th and 40K. The activities of these nuclides were calculated and discussed.

Activation Analysis↗