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

The aim of this study was to evaluate the efficiency of Cerec CAD-CAM grinding discs coated with a standard (StD) and experimental (FeD) diamond pattern using 126 microns and 91 microns diamond grain sizes on each coating. The four types of grinding discs (StD126/91, FeD126/91) were used to mill the same standard mod inlays from blocoff+ (10 x 12 x 15 mm) of feldspathic porcelain (Vita) vs. Dicor MGC glass ceramic (Dentsply). The millings were performed on 12 Cerec units (Siemens) simultaneously for each combination of type of disc and type of material. Using porcelain, the discs milled the following median numbers of inlays: StD126: 6.3, StD91: 3.5 (p less than 0.01) and FeD126: 9.5, FeD91: 8.4. The milling efficiency of FeD91 was significantly (p less than 0.001) higher than that of StD126. Damaging effects on inlay margins were observed; degree 0: StD126 = 35% and FeD126 = 25%; degree 2: StD126 = 10% and FeD126 = 25%. Using Dicor MGC glass ceramic the median number of milled inlays was generally low (StD126: 4.0, StD91: 1.0, FeD126: 3.0, FeD91: 2.0). Damaging degree 3 occurred as follows; StD126 = 2.1%; FeD126 = 4.3%; FeD91 = 0.8%. Concluding from the observed milling efficiency and damaging effects, the standard disc StD126 was judged to offer the best compromise for milling both glass ceramic and porcelain material.
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PMID:[The service life of Cerec abrasive disks]. 165 Sep 64

The radiopacity of two new ceramic restorative materials (Dicor MGC and Cerec Vita Blocks) manufactured for use in producing direct inlays with the 'Cerec CAD-CAM' system was determined. Dicor MGC had a radiopacity significantly greater than that of enamel, while Cerec Vita Blocks had a radiopacity significantly less than that of dentine. It is concluded that Dicor MGC has a radiopacity suitable for its use as an intracoronal restorative for posterior teeth. The low radiopacity of Cerec Vita Blocks means that the use of radiopaque luting cement is essential to permit detection of secondary caries around restorations of this material. Furthermore, marginal overhangs around restorations made from Cerec Vita Blocks will be difficult to detect radiographically.
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PMID:Radiopacity of direct ceramic inlay restoratives. 181 81

The grinding precision of one Cerec-1 (C1) and one Cerec-2 (C2) CAD/CIM unit each was evaluated using standardized inlay-like (mod) samples (n = 40) of Vita Cerec Mk II porcelain and Dicor MGC glass ceramic. Typical dimensions (B, E, F, H) of the sampleS were measured and the standard deviations (SD) analysed statistically using the F-test. SD of C2-machined sample dimensions were significantly lower using both Vita, B: p < 0.05; E: p < 0.001; F: p < 0.001; H: p < 0.001, and Dicor MGC, B: p < 0.05; E: p < 0.001; F: p < 0.001; H: p < 0.01, than those machined with C1, indicating a strong improvement of grinding precision of C2 compared to C1. Accuracy of fit to human molar cavities of mod inlays machined with C1 (n = 6) and C2 (n = 6) was evaluated using a scanning electron microscope with 100x magnification. The width of the interfacial luting gap was generally lower in C2 inlays (56 +/- 27 microns) than with C1 (84 +/- 38 microns). Significant differences (t-test) were seen in margin sections "cervical line angles above CEJ" (C1 = 124 +/- 44/C2 = 59 +/- 30 microns, p < 0.05), "cervical line angles at CEJ" (C1 = 109 +/- 55/C2 = 67 +/- 27 microns, p < 0.05) and "gingival margin above CEJ" (C1 = 81 +/- 32 microns/C2 = 31 +/- 18 microns, p < 0.05).
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PMID:[Grinding precision and accuracy of the fit of Cerec-2 CAD/CIM inlays]. 763 Nov 80

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

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

This in vitro study compared the marginal adaptation of CAD/CAM and laboratory-made ceramic inlays before, during and after loading. Six MOD inlay preparations of standardized design with one cervical margin in dentine and the other in enamel were prepared for each inlay type: CAD/CAM fabricated MGC-glass ceramic inlays, CAD/CAM fabricated feldspathic porcelain inlays, laboratory-made glass ceramic inlays and laboratory-made feldspathic porcelain inlays. Appropriate luting composite materials were used. The restored teeth were subjected to occlusal loading, thermal cycling, toothbrush-toothpaste abrasion and chemical degradation in vitro. Marginal adaptation was quantitated along the entire length of the cavosurface margin and along selected sections of the margin using SEM, following in vitro testing corresponding to 0, 0.5, 1.0, 2.7 and 5.0 years of clinical service. In addition, marginal fit of the cemented inlays was evaluated in the SEM. The initial marginal adaptation in enamel was excellent in all groups. After in vitro testing, significant marginal discrepancies were found in all groups. A high percentage of marginal openings was recorded, notably in the cervical portions of the margins in both enamel and dentine.
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PMID:Marginal adaptation and fit of adhesive ceramic inlays. 842 82

Machinable ceramics (Vita Mark II and Dicor MGC) exhibit good short-term clinical performance, but long-term in vivo fracture resistance is still being monitored. The relatively low fracture toughness of currently available machinable ceramics restricts their use to conservative inlays and onlays. A new machinable glass ceramic (MGC-F) has been developed (Corning Inc.) with enhanced fluorescence and machinability. The purpose of this study was to characterize and compare key mechanical properties of MGC-F to Dicor MGC-Light, Dicor MGC-Dark, and Vita Mark II glass ceramics. The mean fracture toughness and indented biaxial flexure strength of MGC-F were each significantly greater (p < or = 0.01) than that of Dicor MGC-Light, Dicor MGC-Dark, and Vita Mark II ceramic materials. The results of this study indicate the potential for better in vivo fracture resistance of MGC-F compared with existing machinable ceramic materials for CAD/CAM restorations.
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PMID:Mechanical properties of a new mica-based machinable glass ceramic for CAD/CAM restorations. 895 88

Overproduction of the potent vasoconstrictor peptide endothelin-1 (ET-1) is implicated in the pathogenesis of coronary artery disease. In endothelium-denuded human coronary arteries the response to big ET-1 was significantly enhanced in atherosclerotic arteries (coronary artery disease, CAD; n=7) with an EC50 value of 96 nM (57- 161 nM, 95% C.I.) compared to 274 nM (205-365 nM) in non-diseased arteries (dilated cardiomyopathy, DCM; n=10) (Mann-Whitney U-test, P<0.05). Higher levels of immunoreactive endothelin (ET) could be detected by radioimmunoassay in bathing medium taken from CAD arteries than from DCM arteries (2.8+/-0.5 nM, n=5 vs 1.1+/-0.2 nM, n=7) (Student's two-tailed t-test, P<0.05). There were no differences in responses of arteries from either group to ET-1 (EC50 10 nM, CAD vs 14 nM, DCM). The enhanced response of atherosclerotic human coronary arteries to big ET-1 appears to be due to up-regulation of endothelin-converting enzyme (ECE) activity rather than to an augmented response of the arteries to ET-1. This non-endothelial ECE may therefore be an important therapeutic target in coronary artery disease.
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PMID:Increased response to big endothelin-1 in atherosclerotic human coronary artery: functional evidence for up-regulation of endothelin-converting enzyme activity in disease. 978 93

Ceramic materials provide an alternative when choosing a tooth-colored restoration. Currently, posterior composite restorations can be used to achieve esthetic restorations; however, they have many disadvantages with regard to wear, polymerization shrinkage, discoloration, marginal leakage, and technique sensitivity. The use of CEREC CAD/CAM enables the dentist to place feldspathic porcelain (Vitablocs Mark II) and machinable glass ceramic (Dicor MGC) restorations in a single visit. When compared to composite materials, these materials closely approximate the physical properties of enamel in compressive and tensile strength and wear resistance. This study evaluated 50 CEREC CAD/CAM restorations after 4 years in service. Restorations ranged from Class I to 7/8s crown preparations.
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PMID:A new approach to restorative dentistry: fabricating ceramic restorations using CEREC CAD/CAM. 1065 Mar 68

The purpose of this study was to evaluate Cerec CAD/CAM inlays processed of two industrially made machinable ceramics during an 8-yr follow-up period. Each of 16 patients received two similar ceramic inlays. Half the number of the inlays were made of a feldspathic (Vita Mark II) and the other of a glass ceramic (Dicor MGC) block. The inlays were luted with a dual resin composite and evaluated clinically using modified USPHS criteria at baseline, 8 months, 2, 3, 5, 6 and 8 yr, and indirectly using models. At baseline, 84% of the inlays were estimated as optimal and 16% as acceptable. Postoperative sensitivity was reported by one patient for 8 months. Of the 32 inlays evaluated during the 8 yr, 3 failed due to fracture of the material. No secondary caries was found adjacent to the inlays. No significant differences in the clinical performance were found between inlays made of the two ceramics. It can be concluded that the CAD/CAM inlays processed of the two ceramics functioned well during the 8-yr follow-up period.
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PMID:An 8-year evaluation of sintered ceramic and glass ceramic inlays processed by the Cerec CAD/CAM system. 1087 95


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