OBJECTIVETo investigate the color difference between Au-Pt alloy porcelain and Ni-Cr alloy porcelain.

METHODS30 metal-ceramic specimens with different dentin porcelain thickness were fabricated with two types of metal-ceramic alloy, each type of alloy had 15 specimens. L*, a*, b* were measured after opaque porcelain was applied, and dentin porcelain was fired 1, 3, 5, 7 times by MINOLTA CR-100. Then delta E was calculated which reflected the color difference between high-gold alloy porcelain and Ni-Cr alloy porcelain.

RESULTSComparing with Ni-Cr alloy porcelain, the color of Au-Pt alloy porcelain was reddish, yellowish and less bright. The delta E between high-gold alloy porcelain and Ni-Cr alloy porcelain in shade A2 was largest when opaque porcelain was applied. It decreased when dentin porcelain was applied. It became smallest when fired 3 times, and increased along with the increase of fire times. It was larger than 1.5 except firing 3 times. When dentin porcelain was applied, delta E which was larger than 1.5 among different dentin porcelain thickness decreased along with the increase of dentin porcelain thickness.

CONCLUSIONThe color difference between the two types of metal-ceramic alloy should be carefully taken into account in order to improve the quality of color matching.

Chromium ; Chromium Alloys ; Dental Porcelain ; Dental Prosthesis Design ; Gold Alloys ; Humans ; Metal Ceramic Alloys ; Nickel ; Platinum ; Prosthesis Coloring

OBJECTIVETo compare the color differences of different metal bases and different opaque thickness, and evaluate the best thickness of opaque on different metal bases.

METHODSPrecious metal, gold sediment and Ni-Cr plates were prepared as bases, then opaque samples of 0.05, 0.1, 0.2, 0.3, 0.4 and 0.5 mm thickness were fabricated on such plates. Minolta chromatics meter CR-321 was used to examine the color properties of these samples, and deltaE was calculated to evaluate the color difference of the specimens.

RESULTSFor the restoration based on Ni-Cr and precious alloys, the color of restorations was not affected by the color of metal bases as the thickness of opaque reached 0.3 mm, and the chromatic value deltaE < 1.5 NBS. For the restoration based on gold sediment, the color of restoration was not affected by the color of metal as the thickness of opaque reached 0.1 mm, and the chromatic value deltaE < 1.5 NBS.

CONCLUSIONDifferent opaque thickness was necessary to obtain ideal color appearance in clinic. As the opaque thickness increased, the color of restoration based on Ni-Cr and noble metal increased but the color of restoration based on gold sediment decreased.

Color ; Dental Alloys ; Dental Porcelain ; Gold ; Metal Ceramic Alloys

OBJECTIVETo investigate the influences of recasting on the mechanical properties of Au-Pt ceramic alloy.

METHODSAu-Pt ceramic alloy samples were prepared and recast for 3 times without adding any new Au-Pt ceramic alloy. The tensile strength, 0.2% yield strength, percentage of elongation, flexural strength, flexural modulus and Vickers hardness of each specimen were measured.

RESULTSBeing cast for different times, the Au-Pt ceramic alloy showed no significant differences on their tensile strength, 0.2% yield strength, percentage of elongation, flexural strength or Vickers hardness. The flexural modulus of the Au-Pt alloys being cast for 2 or 3 times was significantly higher than that of the alloys being cast for 1 time (P < 0.05). CONCLUSION Au-Pt ceramic alloy can be recast for 3 times at least, without any decrease in the mechanical properties.

Alloys ; Ceramics ; Dental Alloys ; Gold Alloys ; Hardness ; Materials Testing ; Metal Ceramic Alloys ; Tensile Strength

OBJECTIVETo study the effect of solid phase transformation on the metal-ceramic compatibility of Co-Cr alloy during firing programs.

METHODS9 foils of Co-Cr and Ni-Cr alloy with the dimension of 25 mmx3 mmx0.5 mm were casted using lost wax technology respectively. Among them, 6 specimens were subjected to metal-ceramic bonding strength test (three point bending method), the ceramic layer of 3 specimens were removed for X-ray diffraction (XRD) analysis. One cylindrical specimen of each alloy was casted for the test of coefficient of thermal expansion, cooling curves were recorded.

RESULTSThe metal-ceramic bonding strength of Ni-Cr, Co-Cr alloy was (49.1 +/- 3.40), (40.9 +/- 2.02) MPa respectively. There was significant difference between the two groups' bonding strength (P = 0.00). The coefficient of thermal expansion in the 20-500 degrees C interval of Ni-Cr and Co-Cr alloy was 13.9 x 10(-6), 13.8 x 10(-6) x K(-1) respectively. XRD analysis indicated that the microstructure of Ni-Cr alloy was austenite. While Co-Cr alloy was constituted by fcc phase, hcp phase and sigma phase.

CONCLUSIONDuring the cooling procedure, the transformation of fcc phase to hcp phase and segregation of needle-like sigma phase intensify the linear contraction speed of Co-Cr alloy, which decreases the metal-ceramic adaptability.

Alloys ; Ceramics ; Chromium Alloys ; Dental Alloys ; Dental Bonding ; Dental Porcelain ; Materials Testing ; Metal Ceramic Alloys ; Metals

OBJECTIVETo compare the shear bond strength(SBS) of cast Co-Cr alloys and selective laser melting(SLM) Co-Cr alloys with those of dental porcelain.

METHODSA dental porcelain (Vita) was applied on cast and SLM Co-Cr alloy specimens (n = 10). SBS test was conducted, and fracture mode analysis was determined. Student's t-test by SPSS 13.0 software was employed to analyze the data.

RESULTSThe SLM Co-Cr alloy specimens had lower SBS values than the cast Co-Cr alloy specimens (P > 0.05). The metal-porcelain bond strength value of the cast group was (33.11 +/- 4.98) MPa, and that of the SLM group was (30.94 +/- 5.98) MPa. The specimens in both test groups exhibited mixed failure.

CONCLUSIONThe metal-porcelain system processed by SLM exhibit a bond strength that is similar to that of the cast group. This system also display a high precision.

Alloys ; Chromium Alloys ; Dental Alloys ; Dental Porcelain ; Lasers ; Materials Testing ; Metal Ceramic Alloys ; Metals

OBJECTIVETo study the mechanical properties of Co-Cr ceramic alloy after recasts.

METHODSCo-Cr ceramic alloy cast samples were prepared and recast for 3 times without adding any new Co-Cr ceramic alloy. The tensile strength, 0.2% yield strength, percentage of elongation, flexural strength, flexural modulus and Vickers hardness of each specimen were measured.

RESULTSBeing cast for different times, the Co-Cr ceramic alloy showed no significant differences on their tensile strength, 0.2% yield strength, percentage of elongation, flexural strength, flexural modulus and Vickers hardness.

CONCLUSIONCo-Cr ceramic alloy can be recast for 3 times at least, without decrease of the mechanical properties.

Alloys ; Ceramics ; Chromium Alloys ; Dental Stress Analysis ; Hardness ; Materials Testing ; Metal Ceramic Alloys ; Tensile Strength

OBJECTIVETo study the shape, thickness and oxide percentage of major metal element of oxide film on Ni-Cr porcelain alloy after anodizing pretreatment.

METHODS10 samples were made and divided into 2 groups at random. Then after surface pretreatment, the oxide films of two samples of each group were analyzed using electronic scanning microscope. The rest 3 samples were measured by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES).

RESULTSLightly selective solution appeared because the different component parts of the alloy have dissimilar electrode, whose dissolve velocity were quite unlike. The sample's metal surface expanded, so the mechanical interlocking of porcelain and metal increased bond strength. The thickness of oxide film was 1.72 times of the control samples. The oxide percentage of major metal elements such as Cr, Ni and Mo were higher, especially Cr. It initially involved the formation of a thin oxide bound to the alloy and second, the ability of the formed oxide to saturate the porcelain, completing the chemical bond of porcelain to metal.

CONCLUSIONThe method of anodizing Ni-Cr porcelain alloy can easily control the forming of oxide film which was thin and its surface pattern was uniform. It is repeated and a good method of surface pretreatment before firing cycle.

Alloys ; Chromium Alloys ; Dental Porcelain ; Metal Ceramic Alloys ; Microscopy, Electron, Scanning ; Nickel ; Oxides

OBJECTIVETo investigate a kind of Co-Cr-Mo alloys used for both porcelain fused to metal (PFM) restorations and casting framework of removable partial dentures.

METHODSThe Co-Cr-Mo alloy underwent the design for elementary compositions of the alloys and the production from the raw materials by means of a vacuum melt furnace. The strength, hardness, plasticity and casting ability of the alloy were examined with metal tensile test. Vickers hardness test and grid casting were examined respectively. The microstructure of the Co-Cr-Mo alloy was also inspected by scanning electron microscope and X-ray diffraction analysis.

RESULTSThe elementary composition of DA9-4 alloy mainly consisted of Co 54%-67%, Cr 21%-26%, Mo 5%-8%, W 5%-8%, Si 1%-3%, Mn 0.1%-0.25% and trace elements. The yield strength of the alloy was 584 MPa, while the tensile strength was 736 MPa. The coefficient of expansion was 15.0%, the Vickers hardness reached 322, and the casting ratio exibited 100%.

CONCLUSIONThe DA9-4 Co-Cr-Mo alloy used for PFM and framework shown in this paper can meet the clinical demands and have reached the objects of the experiment plan.

Alloys ; Chromium Alloys ; Dental Porcelain ; Hardness ; Materials Testing ; Metal Ceramic Alloys ; Metals ; Surface Properties

STATEMENT OF PROBLEMS: Conventional feldspathic porcelain is used extensively as a restorative material and it is subjected to grinding and polishing during fabrication and delivery procedures. There is still considerable controversy concerning the best methods to achieve the strongest porcelain restorations after such adjustments. PURPOSE: The objective of this study was to investigate the effects of (1) overglazing, (2) selfglazing, and (3) fine polishing on the flexural strength and fracture toughness of feldspathic dental porcelain. MATERIAL AND METHOD: Ninety porcelain disks were prepared for flexural strength test and sixty porcelain disks were fabricated for fracture toughness test. Specimens were divided into three groups for each test as follows: 1) overglazed 2) self-glazed 3) polished. The flexural strength of feldspathic porcelains was determined by ring-on-ring biaxial flexural strength test. The fracture toughness values of three experimental groups were obtained by indentation fracture toughness test. RESULTS: The flexural strength of overglazed group was significantly higher than that of selfglazed and polished group (P<0.05), while the difference between self-glazed and polished group was not significant (P>0.05). The fracture toughness values of overglazed and polished group were significantly higher than that of self-glazed group (P<0.05), while the difference between overglazed and polished group was not significant (P>0.05). CONCLUSIONS: This results supported the use of polishing as an alternative to glazing metal ceramic restorations, as it was not detrimental in flexural strength and fracture toughness. But, under the conditions of this study, overglazing was the ideal surface finishing method of feldspathic dental porcelain.
Dental Porcelain* ; Metal Ceramic Alloys

PURPOSE: The porcelain fused to gold has been widely used as a restoration both with the natural esthetics of the porcelain and durability and marginal fit of metal casting. However, recently, due to the continuous rise in the price of gold, an interest towards materials to replace gold alloy is getting higher. This study compared the bond strength of porcelain to millingable palladium-silver (Pd-Ag) alloy, with that of 3 conventionally used metal-ceramic alloys. MATERIALS AND METHODS: Four types of metal-ceramic alloys, castable nonprecious nickel-chrome alloy, castable precious metal alloys containing 83% and 32% of gold, and millingable Pd-Ag alloy were used to make metal specimens (n=40). And porcelain was applied on the center area of metal specimen. Three-point bending test was performed with universal testing machine. The bond strength data were analyzed with a one-way ANOVA and post hoc Scheffe's tests (alpha=.05). RESULTS: The 3-point bending test showed the strongest (40.42 +/- 5.72 MPa) metal-ceramic bond in the nonprecious Ni-Cr alloy, followed by millingable Pd-Ag alloy (37.71 +/- 2.46 MPa), precious metal alloy containing 83% of gold (35.89 +/- 1.93 MPa), and precious metal alloy containing 32% of gold (34.59 +/- 2.63 MPa). Nonprecious Ni-Cr alloy and precious metal alloy containing 32% of gold showed significant difference (P<.05). CONCLUSION: The type of metal-ceramic alloys affects the bond strength of porcelain. Every metal-ceramic alloy used in this study showed clinically applicable bond strength with porcelain (25 MPa).
Alloys* ; Dental Porcelain* ; Esthetics ; Metal Ceramic Alloys