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ABSTRACT: Color information from different color-measuring systems varies during color matching in maxillofacial prosthetics. We studied the hypothesis that a non-contact measuring system and 4 contact color-measuring instruments perform comparably in accuracy and precision on measurements of pigmented maxillofacial elastomer specimens having human skin colors. Measurement comparisons in accuracy on opaque standard color patches were made in Phase I. In Phase II, the system with the best accuracy was used as the reference instrument, and comparisons in accuracy and precision on elastomer specimens were made. The CIEDE2000 color difference formula was used. Repeated-measures ANOVA with Tukey testing and linear regression analysis for CIELAB and color differences among the instruments were performed. The contact measuring systems perform differently in accuracy, possibly due to edge loss and other factors, but performed comparably in precision with the non-contact measuring instrument. This non-contact system is recommended for color measurement of maxillofacial prosthetic materials.
Journal of dental research 12/2010; 89(12):1522-7. · 3.46 Impact Factor
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ABSTRACT: This study evaluated the wear area of human enamel opposing 2 conventional and 2 low-fusing dental porcelains, as well as abrasive wear, attrition, surface hardness, and fracture toughness for the 4 porcelain substrates.
Two low-fusing and 2 conventional metal-ceramic porcelains were used to form 15-mm-diameter disks (n = 10), which were fired according to manufacturer's recommendations. Enamel cusps (n = 40) were formed from extracted third molars. All ceramic and enamel specimens were finished to a 1000-grit silicon carbide surface. The Oregon Health Sciences University (Portland, OR) oral wear simulator was used to deliver a 20-N load from the cusps to the ceramic substrates through a food-like slurry. The sliding action of the cusps over an 8-mm linear path produced abrasive wear. A static 70-N load was applied at the end of the path to create attrition. This sequence was repeated at 1.0 Hz for 50,000 cycles. Ceramic wear was measured with a profilometer (+/-2 micrometers), and enamel wear was evaluated using optical scanning methods. After wear testing, the hardness and fracture toughness of the ceramic surfaces were determined, and scanning electron photomicrographs were made using representative ceramic and enamel specimens from each group. Enamel wear areas, abrasion and attrition depths, hardness, and fracture toughness values were subjected to analysis of variance and Tukey-Kramer post hoc tests to determine significant differences.
Enamel wear was not significantly different for low-fusing and conventional porcelains (p =.29). The wear of conventional and low-fusing ceramic substrates was also not significantly different (p =.79). However, depth of porcelain wear caused by attrition was in general significantly greater than abrasive wear (p =.0004). Although no significant differences were found in the measured porcelain hardness values (p =.08), 1 conventional porcelain exhibited fracture toughness significantly greater than 1 low-fusing porcelain (p <.01).
No differences in wear patterns were noted among low-fusing compared with conventional metal-ceramic porcelains, but static loading resulted in significantly greater attrition compared with the observed sliding abrasive wear. J Prosthodont 2001;10:8-15.
Journal of Prosthodontics 03/2001; 10(1):8-15. · 1.01 Impact Factor
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ABSTRACT: The purpose of this study was to assess the effect of different high-palladium alloys on the resulting color of opaque porcelain. Three Pd-Cu-Ga alloys, Spartan Plus (S; Williams Dental Co/Division of Ivoclar North America, Amhest, NY), Liberty (B; J.F. Jelenko & Co, Armonk, NY), and Freedom Plus (F; J.F. Jelenko & Co); 4 Pd-Ga alloys, Legacy (L; J.F. Jelenko & Co), IS 85 (I; Williams Dental Co), Protocol (P; Williams Dental Co), and Legacy XT (X; J.F. Jelenko & Co); and a Pd-Ag alloy, Super Star (T; J.F. Jelenko & Co), were examined. The Au-Pd alloy Olympia (O; J.F. Jelenko & Co) served as the control.
Three cast 16-mm discs, 1-mm thick, were prepared from each of the alloys. After metallurgically polishing and air-abrading, the specimens were oxidized following the manufacturer's recommendations. Shade B1 opaque porcelain (Vita-Omega; Vident, Baldwin Park, CA) was applied at a final thickness of 0.1 mm using a mold. After 2 opaque porcelain firing cycles, the surfaces were air-abraded. The colors of the specimens were measured using a colorimeter and expressed in Commission International de l'Eclairage (CIE) L*a*b* coordinates. Color differences (delta E) were determined between the control and each experimental group. Analysis of Variance and Tukey-Kramer tests were performed on the delta E data.
The 3 Pd-Cu-Ga alloys showed significantly greater (p < .01) delta E values (S = 2.8 +/- 1.1, B = 3.0 +/- 0.6, and F = 2.1 +/- 0.2) than the remaining 5 experimental groups (L = 0.7 +/- 0.5, I = 0.7 +/- 0.4, P = 0.7 +/- 0.2, X = 0.7 +/- 0.4, and T = 0.7 +/- 0.5). The directions of the significant color changes were relatively equally distributed along the L*, a*, and b* axes, and all delta L*, delta a*, and delta b* values were negative (lower value, more green and blue relative to control O).
This work suggests that a 0.1-mm-thick layer of opaque porcelain in the Pd-Cu-Ga alloys studied, did not reliably reproduce the color of porcelain.
Journal of Prosthodontics 07/2000; 9(2):71-6. · 1.01 Impact Factor
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ABSTRACT: This in vitro study was designed to evaluate the new ShadeEye-EX Chroma Meter and a new visual porcelain shade-matching system (Vitapan 3-D Master, Omega 900) in comparison to the traditionally used visual porcelain shade-matching system (Vita Lumin Vacuum, VMK 68).
Shade matches and porcelain fabrications on individualized shade tabs were carried out. The fabricated porcelain tabs were evaluated against the respective natural tooth using the United States Public Health Service (USPHS) criteria to determine clinically acceptable match. The tabs also were ranked according to the final-color match to the corresponding natural tooth.
The percentage of clinically acceptable color matches were as follows: Vita Lumin Vacuum (46.67%), ShadeEye-EX (40%), and Vitapan 3-D Master (56.67%). The generalized estimating equation (alpha = 0.5) showed no statistically significant difference between systems in obtaining a clinically acceptable match (p = .5729). The chi-squared test (alpha = 0.5) showed no statistically significant difference between systems in terms of rank order (p = .5017). The two new systems do not produce color match that is better than the conventional visual porcelain shade-matching system.
Journal of esthetic dentistry 02/2000; 12(5):271-80.
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ABSTRACT: This laboratory study was designed to investigate the effect of controlled nanoporosity on the wear resistance of polymeric composites reinforced with silica gel powders and to determine the mechanisms controlling the abrasive wear properties of these unique nanostructured materials.
Silica gels were prepared by hydrolysis and condensation of tetraethylorthosilicate (TEOS) using four different catalysts to modify the porous structure of the resulting polysilicate silanation, an organic monomer (TEGDMA) containing various initiators was introduced into the gel powders to form a paste. The various pastes were then polymerized inside a glass mold. A pin-on-disk apparatus was then used to record the specimen length and number of revolutions. Abrasive wear rates were determined by regression analysis and statistical differences were determined by analysis of variance and multiple comparisons. BET was used to characterize the filler pore structure and scanning electron microscopy was used used to visually examine the abraded surfaces.
Significant differences (p < 0.05) in the wear rates of the experimental composites were noted. Within the range of filler porosities examined, wear resistance was found to be linearly dependent (R2 = 0.983) on filler pore volume. The wear rates decreased with increasing filler porosity. HCl-catalyzed gels having low porosity produced composites having relatively limited abrasion resistance. In contrast, high porosity HF-catalyzed gels produced more wear-resistant composites. The abrasive wear resistance of these nanocomposites was not significantly affected by the level of silane coupling used in these experiments. SEM evaluation suggested that better wear resistance was associated with fine-scale plastic deformation of the wear surface and the absence of filler particle pullout.
Porous particles prepared via sol-gel show some promise as fillers that improve the wear resistance of photopolymerized resins. The wear resistance of the fillers appears to be directly related to nanoporous structure of the gel particles. Unlike conventional dental composites, these materials rely primarily on nanomechanical coupling for improved wear resistance. This new principle should benefit subsequent investigations.
Dental Materials 02/1998; 14(1):29-36. · 3.13 Impact Factor
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ABSTRACT: Edge-losses occur during reflectance measurements of pigmented maxillofacial elastomer when light is scattered within a sample beyond that part of the surface exposed to the observation system of the optical device. A custom sample-holder is presented which redirects light that would not be measured during conventional reflectance measurement back into the sample. The amount of edge-loss occurring within thin layers of maxillofacial elastomer with tan pigment on black-and-white backings was found to depend on sample thickness, the backing, the beam size used during conventional reflectance measurement, and the optical term bS = (2KS + K2)1/2. Data analysis revealed a significant interaction among these four factors. Additionally, the edge-loss occurring during the tristimulus reflectance measurement of thick samples of maxillofacial elastomer with various concentrations of tan and black pigment was found to be linearly related to bS up to a limiting value, with no additional edge-loss occurring for bS values above this limiting value. Edge-loss is an important consideration during the matching of the optical characteristics of pigmented maxillofacial material to those of human skin.
Journal of Dental Research 03/1996; 75(2):752-60. · 3.49 Impact Factor
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ABSTRACT: Dental ceramics can fail through growth of microscopic surface flaws that form during processing or from surface impact during service. New restorative dental ceramic materials have been developed to improve resistance to crack propagation. Eleven of these improved materials with the common feature of a considerable amount of crystalline phase in the glassy matrix were evaluated. The ceramic materials studied included fluormica-, leucite-, alumina-, and zirconia-reinforced glasses. The relative hardness and fracture toughness were determined by indentation technique. Alumina-reinforced materials resulted in the highest fracture toughness values, whereas the fluormica- and leucite-reinfoced materials showed more moderate but statistically significant greater values compared with those of control materials. The hardness values of ceramic materials with improved fracture toughness were both substantially higher or lower than those of the control groups and suggested a lack of direct correlation between these two properties. Selection of appropriate restorative materials depends on clinical application and requires consideration of several physical properties including fracture toughness.
Journal of Prosthetic Dentistry 09/1995; 74(2):145-50. · 1.32 Impact Factor
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ABSTRACT: The purpose of this study was to determine the moduli of rupture of layered beams made of strong core materials veneered with weaker conventional feldspathic porcelain.
A three-point flexural test, and formulae derived especially for this purpose were used. Two systems were investigated. The first consisted of Vitadur N (Vita Zahnfabrik), a conventional feldspathic porcelain; and Dicor MGC (L.D. Caulk), a machinable glass ceramic. The second consisted of Vitadur N and In-Ceram (Vita Zahnfabrik), a strong reinforced aluminous porcelain.
Two-way ANOVA and Tukey tests were used to evaluate the effect of numerous factors on the modulus of rupture. The results indicated that the material forming the tensile surface, the material forming the compressive surface and their interaction had a highly significant effect on modulus of rupture (p < 0.05). The effect of the material forming the tensile surface on modulus of rupture was of much greater magnitude than that of the compressive surface. Theoretical curves describing effects of the layers' elastic moduli and thickness on the force-bearing capacity of model beams were plotted. These indicated that for a wide range of thickness ratios and for a wide variety of elastic modulus ratios, the tensile material dominates the force-bearing capacity of layered beams except when a very much lower modulus material forms the compressive layer.
Layered prostheses made of strong cores veneered with weaker feldspathic porcelain may be prone to failure when the feldspathic surfaces are subjected to tensile force.
Dental Materials 02/1994; 10(1):52-8. · 3.13 Impact Factor
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ABSTRACT: The purpose of the present investigation was to determine whether high-resolution carbon-13 nuclear magnetic resonance could be utilized for detection of ionic bonding interactions of NPG and NPG-GMA with selected inorganic cations. The C1-carbonyl carbon of NPG and NPG-GMA were labeled with 13C to help magnify the spectral response signal. The labeled monomers were allowed to react with Ca(OH)2 and LiOH. The C-13 carbonyl resonance was observed by solution- and solid-state NMR. The interaction of the cations in solution and on a powered glass support resulted in a downfield chemical shift of about 2-5 ppm, indicating the presence of a chemical interaction between the monomer and the cations. The reaction of the monomers with the solid substrates of hydroxyapatite, and bovine dentin did not result in a significant downfield shift in the carbonyl resonance. The results provide evidence that high-resolution nuclear magnetic resonance can be used for evaluation of chemical bonding interactions of dental adhesives with inorganic ions.
Journal of Dental Research 02/1993; 72(1):72-7. · 3.49 Impact Factor
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ABSTRACT: The kinetics of ion exchange strengthening of three feldspathic porcelains were investigated. Data describing the effects of treatment time and temperature on flexural strength were produced. The temperature effect results support the hypothesis that the opposing phenomena of diffusion and relaxation control residual stress. The time effect results suggest that Fick's Law of diffusion and diffusional creep control flexural strength. Mechanisms were proposed. These findings suggest that precise control of temperature is more critical than control of time in this process of ion strengthening. Further investigations on the ion strengthening of low-fusing porcelains should be carried out.
Dental Materials 10/1992; 8(5):320-3. · 3.13 Impact Factor
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ABSTRACT: The application of home-bleaching procedures as a means of lightening multiple teeth has become increasingly popular. Very few studies, however, have determined the effect of this treatment upon dental hard tissues. This in vitro study evaluated the effects of a 10% carbamide peroxide gel on the apparent fracture toughness, hardness, and abrasion characteristics of human enamel. The apparent fracture toughness of enamel was reduced by about 30% after bleaching for a period of 12 hours with no significant change in surface hardness. Enamel treated with the bleaching gels also exhibited a small but significant decrease in abrasion resistance. This behavior was most likely due to an alteration of the organic matrix of enamel under the chemical action of hydrogen peroxide. Further investigation of the clinical significance of this process is needed.
Journal of Dental Research 07/1992; 71(6):1340-4. · 3.49 Impact Factor
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ABSTRACT: The swaged metal matrix provides a method for rapidly making a metal substructure for ceramic crowns. This study determined the vertical and horizontal marginal fidelity of swaged metal substrate crowns made with four methods. No significant difference in vertical or horizontal marginal fidelity was found for metal margin crowns formed with either a plastic spacer or a paint-on die spacer. The vertical marginal fidelity was significantly better in crowns made with a metal margin (37 microns) than in crowns made with a porcelain facial margin (62 microns), and the latter were significantly better than crowns made with a 360-degrees porcelain margin (86 microns). Crowns made with all four methods were overcontoured by 46 to 82 microns. The 360-degrees porcelain margin was technically more difficult and time-consuming to make.
Journal of Prosthetic Dentistry 03/1992; 67(2):162-73. · 1.32 Impact Factor
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ABSTRACT: Manufacturers generally quote indentation hardness values when predicting the clinical wear potential of newly introduced ceramic restoratives. The objective of this study was to determine whether in vitro two-body wear correlated well with hardness. A modified polisher was used to abrade enamel cylinders against polished disks of commercially available dental porcelains and glass. Enamel loss after four h was measured with a micrometer. Five ceramic materials were tested, and enamel abrasion rates were correlated with Knoop hardness values. Dicor and Dicor coated with a shading porcelain were found to cause the lowest wear of enamel. These rates were statistically significantly lower than those obtained with Optec, the most abrasive material. These findings may be due to microstructural differences between the materials. Knoop hardness showed poor correlation with the results of the abrasive testing.
Journal of Dental Research 04/1991; 70(3):221-5. · 3.49 Impact Factor
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ABSTRACT: Certain metal ceramic alloys alter the final color of bonded porcelain. Contradicting results, inconsistent test designs, and incomplete alloy selections have led to some confusion. In this study, differential colorimetric analysis was done at the opaque and dentin porcelain stages with five major types of metal ceramic alloys. The color stability of the porcelain on the high-noble metal alloys was found to be excellent. The palladium-silver and nickel-chromium alloys resulted in significant color changes of the dentin porcelain only. The greatest changes in color were found with the palladium-silver alloy, which resulted in a higher yellow-green saturation. The nickel-chromium alloy also produced a color change, although not as severe, resulting in a porcelain shade with a reduced Value or lightness.
Journal of Prosthetic Dentistry 04/1991; 65(3):351-6. · 1.32 Impact Factor
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ABSTRACT: The relative flexural strengths of ten brands of dental restorative ceramics were evaluated by a three-point bending test. The materials consisted of three low-fusing and one high-fusing feldspathic porcelains and six reinforced dental restorative ceramics which are currently in clinical use. The reinforced ceramic materials investigated utilized a number of different strengthening processes, including alumina and ceramic fiber reinforcement and controlled crystallization. The results of the investigation indicate that significant differences exist among the measured breaking strengths of the various materials. The processes of controlled crystallization and alumina reinforcement appear to be adequate means of improving the bending strength of restorative dental ceramics.
Dental Materials 08/1990; 6(3):181-4. · 3.13 Impact Factor
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R R Seghi
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ABSTRACT: Recent developments in optical electronic instrumentation for color control have made the potential use of clinical photometric analysis a future possibility for dental materials selection and custom restoration design. The development of such instrumentation will require a more complete understanding of the performance of current technologies on translucent materials. This study was designed to evaluate the effects of instrument-measuring geometry on color-difference assessments made on dental porcelains. The results indicate that a high degree of correlation can exist between color-difference measurements regardless of the design of the instrument-measuring geometry. This work suggests that the development of clinically useful devices need not be restricted to more traditional integrating-sphere-type designs and that more photometrically efficient alternative designs should be explored.
Journal of Dental Research 06/1990; 69(5):1180-3. · 3.49 Impact Factor
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ABSTRACT: We evaluated three shades of nine light-cured composites to determine the colorimetric changes which occur as a result of the photo-polymerization reaction. A photo-electric tristimulus colorimeter was used to measure the color of a 0.5-mm-thick sample of composite on two different backgrounds before and after the polymerization process had been initiated. The results showed that each of the photo-initiated composites tested produced a visually significant change in color as a result of the polymerization reaction, regardless of the shade of the backing. In general, the light-cured composites produced a characteristic chromatic shift toward the blue region of color space, which resulted in a perceived decrease in yellow chroma. Therefore, direct shade selection of a resin composite which is more yellow or more chromatic than the tooth which is being restored is recommended to compensate for this characteristic immediate color shift.
Dental Materials 05/1990; 6(2):133-7. · 3.13 Impact Factor
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ABSTRACT: The CIELAB colorimetric system was used for the study of the relationship between measured color difference values and human observer responses. This study verified that a specific, visually meaningful and precise relationship exists between the magnitude and direction of the measurements and the average dental-observer responses. The results support the use of this system in dentistry as a means of evaluating color by differences. The further development of such systems for clinical use would be warranted and could serve as a valuable tool for material selection and restoration design, particularly in the area of aesthetic restorative dentistry.
Journal of Dental Research 01/1990; 68(12):1760-4. · 3.49 Impact Factor
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ABSTRACT: The selection of an appropriate material that duplicates the appearance of natural tooth structure is very important in restorative dentistry. Photometric and colorimetric analysis techniques offer great potential as a tool for aiding in the duplication process. The degree to which these techniques will be useful depends on the accuracy and precision with which they can be applied to translucent as well as opaque surfaces. The purpose of this investigation was to evaluate the performance of three currently-available photometric devices. The performance capabilities of the instruments were tested on various shades of opaque and translucent dental porcelain surfaces. The performance tests were designed for evaluation of the accuracy and precision of the instrument relative to a well-studied reference instrument. CIELAB color difference metrics were used for the performance analysis. The results revealed that each of the photometric instruments evaluated was capable of producing color measurements with precision. However, the degree of accuracy with which the color measurements were made varied depending on the instrument used and the type of material surface being measured. A photo-electric tristimulus colorimeter showed the best overall performance on the porcelain surfaces, supporting its use as a valuable tool for evaluating color in dentistry.
Journal of Dental Research 01/1990; 68(12):1755-9. · 3.49 Impact Factor
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ABSTRACT: Spectrophotometric measuring techniques were used to determine the color of four corresponding shades of three brands of metal-fusing porcelain systems. The color was expressed in terms of CIE L*a*b* color coordinates. The relationship of these values to the more commonly used attributes of Hue, lightness (Value), and saturation (Chroma) respectively were discussed. The location of the porcelain shades in the color space and the direction of the color differences found between the different brands of porcelain were evaluated. Color differences for each paired comparison within each shade group were determined from the color data. These values represent the magnitude of color differences found between brands and have a direct relationship to visual perceptibility. For the brands and shades measured, the following conclusions can be made: The CIELAB color system provides an objective technique for evaluating the color of dental porcelains. Corresponding shades of different brands of porcelain can produce perceivably different colors. The perceived color differences between the brands were mostly a result of differences in all three color directions. Greater color differences were found to exist between the corresponding opaque porcelains than between the corresponding layered samples. The addition of 1 mm of body porcelain to the opaque compensated to a large extent for the greater color differences found between the corresponding opaques. The results of this study have significant clinical ramifications. Variations in optical characteristics of porcelains produced by different manufacturers add to the problem of color control in ceramic crown fabrication.(ABSTRACT TRUNCATED AT 250 WORDS)
Journal of Prosthetic Dentistry 08/1986; 56(1):35-40. · 1.32 Impact Factor
