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 4,420 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The objective of the preliminary work reported here was to prepare an improved formulation of intrinsically colored microcrystalline glass-ceramic. Applications could include "megafillers" for direct composite restorations, precision castings, and CAD-CAM prostheses. The experimental glass-ceramic reported here contained SiO2 56.9, AI2O3 19, LiO2 7, ZnO 6, MgO 5, TiO22, ZrO22, P2O52, and CeO20.1 mole%. The batch materials were melted and stirred at 1,610 degrees C for 2 h, quenched in water and also formed into a block of a clear, slightly yellow glass. To identify the crystalline phases that developed during transformation of the glass to the ceramic, x-ray diffraction was used on ten aliquots taken during 15 h of stepwise heating from 750 to 1050 degrees C. With heating, the yellow color deepened to a very translucent "dark yellow" dental shade, then lightened with gradually increasing opacity during formation of secondary crystalline phases. X-ray opacity was approximately equivalent to that of dental enamel. The refractive index of the glass, nD1.554, increased during nucleation and growth of the crystalline phases to a maximum of 1.586. Intrinsic coloration of these glass-ceramic materials can be controlled by varying the heat treatment and/or composition to match typical dental shades.
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PMID:An esthetic glass-ceramic for use in composite restoration inserts. 799 79

Improvement of the CAD process to design the shape of crown restorations of a 6 die was carried out by including the bite data of the antagonistic tooth in addition to the data measured in the previous paper. Initially, the position adjustment of the crown data with the bite data in the centric occlusion was attempted. After fixation of the crown data to a suitable position, modulation of the occlusal surface by the functionally generated path (FGP) data was carried out. To connect between the end of the crown data and the margin, a parabolic function was used instead of the B-Spline function used in the previous paper. As a result, the data points were connected more smoothly. Thus, CAD data which were composed of the die data, the crown data, and the connecting data were accomplished. They will be used as the basic data to CAM.
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PMID:Improvement of CAD to produce crown by considering occlusion. 800 13

A computer aided design/computer aided manufacture (CAD CAM) brim measurement adapter was designed for use with a Berkeley casting stand. This measurement adapter accommodates all IPOS/CANFIT-PLUS transfemoral brim sizes and shapes, allows brim positioning, provides adequate stability, and provides a substantial cost saving by using existing, functional hardware as a base.
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PMID:A trans-femoral brim adapter for CAD CAM measurements. 808 48

Conventional and CAD-CAM ceramic restorations often require adjustments that result in a need to reduce surface roughness. Surface roughness resulting from five polishing systems on two ceramics was assessed. Disks of Ceramco II and Dicor MGC ceramic blocks were polished with five combinations of 45, 25, and 10 microns diamonds; a 30-fluted carbide; three silicon carbide-impregnated rubber points; 4 and 1 micron diamond gels; and an aluminum oxide point and two aluminum oxide pastes. Five profilometer average roughness measurements (Ra) were taken of five replications of each step in each sequence. Controls were autoglazed Ceramco II and Dicor MGC ceramic specimens milled with a Cerec diamond wheel. Feldspathic porcelain could be polished smoother than glazed. Dicor ceramic could be polished smoother than Ceramco II ceramic. Finishing diamond points followed by diamond gels produced the smoothest surface. A 30-fluted carbide did not improve smoothness as used. The aluminum oxide point followed by aluminum oxide pastes was equivalent to finishing diamonds and gels for Dicor ceramic.
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PMID:Surface roughness of two polished ceramic materials. 812 73

This study is an evaluation, from the patient's point of view, of CAD CAM prosthesis sockets compared with conventional sockets. Twenty-two trans-tibial amputees were divided into two groups. One group was provided with a CAD CAM (CAPOD) socket, the other with a conventionally made one. After one month the groups were evaluated with regard to subjective experience, the judgement of a prosthetist and a physiotherapist, social variables and objective gait parameters. Then the groups switched over to the other type of socket, and after another month a new evaluation was performed. The study design was a single-blind study. In total 175 variables were evaluated. No difference was found between the two types of socket, except for a lower number of terry cloth stockings used in the CAD CAM socket. As the standard of conventional prosthetics in Sweden is considered to be high, the results were considered as satisfactory. The quality of the CAD CAM sockets was at least at the same level as conventionally made ones.
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PMID:Clinical evaluation of trans-tibial prosthesis sockets: a comparison between CAD CAM and conventionally produced sockets. 813 76

A time-sharing technique for a CAD-CAM unit can avoid scheduling difficulties and lengthy appointments. Dentists can also share the cost of expensive equipment and involve staff in learning the steps of this computer-aided design and manufacture.
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PMID:CAD-CAM ceramic inlays and onlays: using an indirect technique. 817 77

For three years now, it has been possible to find a number of dental CAD/CAM systems. i.e. systems that can produce dental prostheses with robots or computers, on the market. These systems use palpation devices or cameras to make impressions. They either transmit the data to produce the die, the counter die or some intermediate elements directly, or use the possibilities of the computer to reconstruct the most simple pieces or the most complex prostheses on a monitor. In the latter case, CAD/CAM systems--in the full sense of the word--produce a model on a monitor before manufacturing the prosthesis. According to this study, all the systems belong to the same family but their performance as well as their costs and their clinical testing vary considerably. A more detailed analysis would therefore be required. Nevertheless, the CAD/CAM remains the only known prosthetic alternative for the future.
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PMID:The practical dental CAD/CAM in 1993. 833 48

As the CAD-CAM technique has been expanded to include porcelain facings, of particular interest is adapting the veneer to the prepared surface. In a comparison of the gap dimension of CAD-CAM generated veneers to those produced in the laboratory, no statistically significant differences were detected.
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PMID:Evaluating CAD-CAM generated ceramic veneers. 834 May 47

The life of diamond-coated discs during CAD/CAM machining of ceramic inlays was evaluated using the standard hydro-drive (H) and an electric drive (E) as a part of the Cerec 3rd generation unit. E-drive discs (40 mm diameter, 0.5 mm thickness) with four experimental diamond coatings, i.e. different grain sizes, E126 (106-125 microns), E64 (53-63 microns), E46-3 (38-45 microns; triple coating), E46-1 (38-45 microns; single coating) were used. The standard H-drive disc (30 mm diameter, 0.3 mm thickness) and H126 (106-125 microns) coating were used as a control. The same standard mesio-occluso-distal molar inlay was machined from blocks (size 1-8) of Dicor MGC light glass-ceramic and of Vita MkII feldspathic fine porcelain as many times as possible with one disc in each group and the number of machined inlays per disc was counted. Additionally the edge roughness (Ra) of the machined inlays was measured using a Talysurf 50 instrument. The numbers of inlays machined with H126 were 21 porcelain/12 glass-ceramic inlays. The numbers of inlays machined from porcelain/glass-ceramic with the E-drive test discs were E126: 180/68; E64: 93/29; E46-3: 80/21 and E46-1 (current limited to 2.5 ampere): 44/19 inlays. The edge roughness of porcelain/glass-ceramic inlays machined with the E-drive discs was significantly lower than the roughness of inlays machined using the H-drive. E126: 16% (p < 0.05)/43% (p < 0.001); E64: 49%/66%; E46-1: 62%/73%; E46-3: 83%/87% (all differences p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Efficiency and margin quality in the computer-assisted molding and grinding of ceramic inlays]. 835 20

The recently developed nanoindentation technique was used to measure hardness and Young's modulus of small filler particles in resin composites and other dental restoratives. This technique eliminates the need to visualize indentations. Load and displacement are continuously monitored during a loading-unloading sequence, and hardness as well as Young's modulus are then calculated from the load-displacement curves taking into account the geometry of the indenter. Thirteen posterior composites, 3 dental ceramics for CAD/CAM restorations, 1 sintered porcelain, and 1 amalgam were investigated in this study. The results were compared to the hardness and Young's modulus determined by nanoindentation of human enamel. Of the dental materials tested, only five materials contain inorganic filler particles with a nanohardness not statistically different from that of enamel. The predominant fillers in all other materials, except amalgam and the prepolymerized resin fillers in Bell Firm PX, were found to be significantly harder. The dental restorative materials, except the alloy phase in amalgam, were composed of particles with a Young's modulus significantly lower than that of human enamel. The alloy phase in amalgam had a Young's modulus value comparable to that of enamel.
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PMID:Hardness and Young's modulus determined by nanoindentation technique of filler particles of dental restorative materials compared with human enamel. 840 4


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