Microstructure and homogeneity of dental porcelain frits.
The microstructure and homogeneity of three commercial dentin and incisal unfired porcelain frits (one conventional and two ultra-low fusing types, fused-to metal were analyzed by X-ray diffractometry, scanning electron microspectroscopy, and wavelength- and energy dispersive X-ray microspectroscopy. The average contents of tetragonal and cubic leucite for the conventional and one of the ultra-low fusing type frits were 20.1-22.6 wt% and 0-2.6 wt%, respectively, whereas those of another of the ultra-low fusing type frits were about 11.5-11.6 wt% and 2.9-4.6 wt%, respectively. The conventional type frits seemed to be admixtures of three kinds of glass frits. One of the ultra-low fusing type frits seemed to be an admixture of four kinds of glass frits. Another ultra-low fusing frits seemed to be only one kind of glass frit dispersed with small size, less than 1 micron, leucite crystals. There were no remarkable differences in microstructure and homogeneity between dentin and incisal porcelain frits in each brand. (+info)
Porcelain esthetics for the 21st century.
BACKGROUND: Dental procedures play a vital role in the modern dental practice. Considerable research has addressed improvements in the properties of dental porcelains. CLINICAL IMPLICATIONS: This article examines the trends in the scientific advances in dental porcelains. It highlights properties of the new low-fusing porcelains and describes indications for their use. New luting cements also are addressed. (+info)
The Procera abutment--the fifth generation abutment for dental implants.
The Branemark dental implant has undergone progressive development in terms of both the implant body itself and the components connecting the implant to the prosthesis. Many screw and abutment designs have been developed, with various degrees of success. About 15 years ago, CAD (computer-assisted design)-CAM (computer-assisted manufacture) technology was introduced to dentists. More recently CAD-CAM has been used in the manufacture of abutments for implants. This article reviews currently available techniques for creating the Procera custom abutment (Nobel Biocare, Goteborg, Sweden) and outlines appropriate applications for this type of implant. (+info)
Development of Ag-Pd-Au-Cu alloy for multiple dental applications. Part 1. Effects of Pd and Cu contents, and addition of Ga or Sn on physical properties and bond with ultra-low fusing ceramic.
Ag-Pd-Au-Cu quaternary alloys consisting of 30-50% Ag, 20-40% Pd, 10-20% Cu and 20% Au (mother alloys) were prepared. Then 5% Sn or 5% Ga was added to the mother alloy compositions, and another two alloy systems (Sn-added alloys and Ga-added alloys) were also prepared. The bond between the prepared alloys and an ultra-low fusing ceramic as well as their physical properties such as the solidus point, liquidus point and the coefficient of thermal expansion were evaluated. The solidus point and liquidus point of the prepared alloys ranged from 802 degrees C to 1142 degrees C and from 931 degrees C to 1223 degrees C, respectively. The coefficient of thermal expansion ranged from 14.6 to 17.1 x 10(-6)/degrees C for the Sn- and Ga-added alloys. In most cases, the Pd and Cu contents significantly influenced the solidus point, liquidus point and coefficient of thermal expansion. All Sn- and Ga-added alloys showed high area fractions of retained ceramic (92.1-100%), while the mother alloy showed relatively low area fractions (82.3%) with a high standard deviation (20.5%). Based on the evaluated properties, six Sn-added alloys and four Ga-added alloys among the prepared alloys were suitable for the application of the tested ultra-low fusing ceramic. (+info)
Development of Ag-Pd-Au-Cu alloys for multiple dental applications. Part 2. Mechanical properties of experimental Ag-Pd-Au-Cu alloys containing Sn or Ga for ceramic-metal restorations.
Eighteen Ag-Pd-Au-Cu alloys, consisting of nine Ag-Pd-Au-Cu mother compositions (Pd: 20, 30 or 40%, Au: 20%, Cu: 10, 15 or 20%, Ag: balance) containing either 5% Sn or 5% Ga as an additive metal, were experimentally prepared. Tensile strength, proof stress, elongation, elastic modulus, and Vickers hardness of these alloys were evaluated to clarify the potential of these alloys for use as ceramic-metal restorations as well as the effects of the Pd and Cu contents on their mechanical properties. The tensile strength, proof stress, elongation, elastic modulus and Vickers hardness of the 18 experimental alloys were in the range of 410.0-984.0 MPa, 289.7-774.3 MPa, 2.2-23.7%, 81.3-123.0 GPa and 135.7-332.3 HV1, respectively. Ten of the 18 experimental alloys can be used for ultra-low fusing ceramics based on their proof stress, elastic modulus, elongation and hardness. Between the Ga- and Sn-added alloys, differences in tensile strength, proof stress, elongation and hardness were found at several Ag-Pd-Au-Cu compositions. (+info)
Phase transformation of a zirconia ceramic head after total hip arthroplasty.
We report two cases of surface deterioration of a zirconia ceramic femoral head associated with phase transformation after total hip arthroplasty. One head was retrieved at revision due to recurrent dislocation after six years and the other because of failure of the locking mechanism of the polyethylene liner after three years. The monoclinic content of the zirconia ceramics rose from 1% to about 30% on the surface of the heads. SEM revealed numerous craters indicating extraction of the zirconia ceramics at the surface. Surface roughness increased from an initial value of 0.006 microm up to 0.12 microm. This is the first report to show that phase transformation of zirconia ceramics causes deterioration of the surface roughness of the head in vivo after total hip arthroplasty. (+info)
Effects of Sn, Ga, and In additives on properties of Ag-Pd-Au-Cu alloy for ultra-low fusing ceramics.
Nine 35% Ag-30% Pd-20% Au-15% Cu alloys containing 2, 4 and 6 mass% of Sn, Ga or In as an additive metal were experimentally prepared to investigate the effects of different additives and their content on the physical and mechanical properties as well as the bond with a ultra-low fusing ceramic. Both the different additives and their content or either of these two factors significantly influenced most of the evaluated properties except for the area fraction of the retained ceramic. Based on the evaluated properties three experimental alloys (2% Sn-added alloy, 4% Ga-added alloy and 2% In-added alloy) can be recommended as a suitable alloy for ceramic-metal restorations using ultra-low fusing ceramics. (+info)
Evaluation of brittleness of porcelain fused to pure titanium by fracture toughness, hardness and fracture energy.
To elucidate the cause of brittleness of porcelain fused to pure titanium (PFPT) which leads to chipping and cracking similar to that of conventional porcelain in clinical use, fracture toughness KIc, hardness (Hv and Hk) and fracture energy gamma reflecting the bonding energy of atoms were evaluated. In KIc there were no differences between PFPT and conventional porcelain, nor for Hv and Hk, but for the gamma of PFPT calculated from the KIc and the Young modulus measured by the resonance method there was less than that of conventional porcelain. These results indicate that mechanical properties such as KIc and hardness cannot always substantiate the brittleness of PFPT experienced in practical use. However, a comparatively small gamma of PFPT may suggest a fatigue crack growth as a more likely phenomenon as it occurs more easily than the conventional one in oral. (+info)