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Colorimetric evaluation of the influence of five different restorative materials on the color of veneered densely sintered alumina.

PURPOSE: Since the introduction of densely sintered alumina ceramic material in prosthetic dentistry for the fabrication of all-ceramic crowns, no scientific data have been presented on the color of these restorations in combination with different restorative materials. The purpose of this in vitro study was to evaluate the influence of five different restorative materials used for implant abutments or posts and cores on the color of veneered densely sintered alumina. MATERIALS AND METHODS: Sixty discs, 0.6 mm in thickness and 10 mm in diameter, were made out of densely sintered alumina ceramic material (Procera, Nobel Biocare, Gothenburg, Sweden) and veneered using feldspathic porcelain (AllCeram, Ducera, Rosbach, Germany) for a total thickness of 2 mm. Ten of the discs were evaluated colorimetrically using the CIE, L*, a*, b* system (control group). In addition, 50 discs, 3 mm in thickness and identical diameter, were fabricated using the following restorative materials (five different materials used on 10 specimens each): (1) high-precious gold alloy, (2) aluminum-oxide ceramic material, (3) titanium metal alloy, (4) yttrium-stabilized zirconium dioxide ceramic material, and (5) glass-ceramic material. The 50 veneered densely sintered alumina specimens were bonded to the 50 restorative specimens using an autopolymerizing luting composite. L*, a*, b* color coordinates were measured 10 times for each veneered densely sintered alumina specimen. Color differences were calculated using the equation DeltaE = [(DeltaL*)2 + (Deltaa*)2 + (Deltab*)2] 1/2. DeltaE values correspond to differences between the control group and each of the five materials groups. RESULTS: Mean color differences (DeltaE) and SDs for each group were as follows: DeltaE (1) = 1.42 +/- 0.5, DeltaE (2) = 1.53 +/- 0.5, DeltaE (3) = 1.55 +/- 0.4, DeltaE (4) = 1.95 +/- 0.5, DeltaE (5) = 1.23 +/- 0.3. All restorative materials induced changes to the densely sintered alumina color relative to the original color. One-way analysis of variance (ANOVA) tests showed statistically significant differences in DeltaE between the groups; however, the Student-Newman-Keuls test revealed that the only statistically significant difference was between groups 4 and 5. Color differences between the groups were not visually perceivable (DeltaE < 2). CLINICAL SIGNIFICANCE: Within the limits of this in vitro study, veneered densely sintered alumina adhesively fixed with dentine-like cement, successfully masks the shade of different metal or ceramic restorative materials.

Aluminum Oxide↗

Tooth color measurement using Chroma Meter: techniques, advantages, and disadvantages.

UNLABELLED: Tooth whitening has become a popular and routine dental procedure, and its efficacy and safety have been well documented. However, the measurement of tooth color, particularly in the evaluation of the efficacy of a system intended to enhance tooth whiteness, remains a challenge. One of the instruments used for assessing tooth color in clinical whitening studies is the Minolta Chroma Meter CR-321 (Minolta Corporation USA, Ramsey, NJ, USA). This article describes the instrument and discusses various measuring procedures and the Chroma Meter's advantages, limitations, and disadvantages. The available information indicates that, although Minolta Chroma Meter CR-321 provides quantitative and objective measurements of tooth color, it can be tedious to use with a custom alignment device. The Chroma Meter data are inconsistent with the commonly used visual instruments such as Vitapan Classical Shade Guide (Vita Zahnfabrik, Bad Säckingen, Germany), although in many cases the general trends are similar. It is also questionable whether the small area measured adequately represents the color of the whole tooth. A more critical challenge is the lack of methods for interpreting the Chroma Meter data regarding tooth color change in studies evaluating the efficacy of whitening systems. Consequently, at present the Chroma Meter data alone do not appear to be adequate for determining tooth color change in whitening research, although the quantitative measurements may be useful as supplemental or supportive data. Research is needed to develop and improve the instrument and technique for quantitative measurement of tooth color and interpretation of the data for evaluating tooth color change. CLINICAL SIGNIFICANCE: This paper will help readers to understand the advantages and limitations of the Minolta Chroma Meter used for evaluating the efficacy of tooth-whitening systems so that proper judgment can be made in the interpretation of the results of clinical studies.

Color↗

Hepatocellular carcinoma treatment with percutaneous ethanol injection: evaluation with contrast-enhanced color Doppler US.

PURPOSE: To investigate the ability of contrast agent-enhanced color Doppler ultrasonography (US) in evaluating the response of hepatocellular carcinoma (HCC) to percutaneous ethanol injection (PEI). MATERIALS AND METHODS: Forty-two patients (36 men, six women; age range, 51-79 years) with 54 1.3-7.0-cm-diameter (mean +/- SD, 2.8 cm +/- 1.1) HCC lesions were examined with contrast-enhanced color Doppler US before and after PEI. Spiral computed tomography (CT) and percutaneous biopsy also were performed to establish the outcome of therapy. RESULTS: Before PEI, intratumoral color signals were demonstrated at contrast-enhanced color Doppler US in 47 (87%) lesions (in 40 patients). After PEI, blood flow signals were no longer detected in all 34 of the lesions that were found to be necrotic at spiral CT and biopsy. In 12 (92%) of 13 lesions containing residual viable tumor, intratumoral color signals corresponding to the enhancing areas at spiral CT were still identified at contrast-enhanced color Doppler US. These 12 lesions were retreated with PEI by targeting the areas of residual tumor with contrast-enhanced color Doppler US guidance. Complete necrosis was seen after the second PEI cycle in nine of 12 lesions. CONCLUSION: Contrast-enhanced color Doppler US shows promise in assessing the therapeutic effect of PEI on HCC and in guiding additional treatment in cases of incomplete response.

Aged↗

Color vision mechanisms in monkey striate cortex: dual-opponent cells with concentric receptive fields.

1. I have recorded with tungsten microelectrodes from single cells in the monkey's visual cortex and have specifically studied those neurons which were sensitive to the color of the stimulus. In the primate striate cortex there are four classes of color-coded cells. The cells described in this paper have concentric receptive fields with one red-green opponent-color system in the field center and the opposite organization in the surround. These dual-opponent cells were nost sensitive to the simultaneous presentation of two different colors, one covering the field center and the other illuminating the surround. They are probable involved in the perception of simultaneous color-contrast phenomena. 2. Spectral sensitivity curves revealed that both the field centers and the surrounds received opposite types of inputs from red-sensitive and green-sensitive cones. None of the cells tested had inputs from rods. 3. Area-sensitivity curves showed that peripheral suppression was present for both phases of the center opponent-color system. The boundary between the center and the surround was the same for both sets of opponent systems. Some cells had "silent" surrounds, which did not respond to annular stimuli. 4. Multiple-unit recordings from a concentric cell and one of its presumed afferents yielded information regarding its possible synaptic inputs. In some cases the cells appeared to receive contacts from red/green opponent-color geniculated fibers with circular receptive fields that lacked an antagonistic surround (similar to Wiesel and Hubel's (37) type II class). In other instances the afferents had on-center, off surround receptive fields or the reverse, but received inputs from only one cone type, either red or green (similar to Wiesel and Hubel's type III class). 5. Concentric cells were always driven by only one eye. 6. The laminar distribution of these cells was limited almost entirely to layer IV and its subdivisions. 7. The cumulative evidence presented in this paper indicates that the concentric cells probably received direct geniculate inputs and, therefore, they are the first cortical stage in the integration of color-contrast information.

Animals↗

Spectral bandwidths of color-opponent cells of geniculocortical pathway of macaque monkeys.

1. The spectral-response bandwidth and peak sensitivity of the responses of color-opponent retinal ganglion cells of the macaque monkey were examined in conditions of neutral adaptation. Color-opponent cells showed specific "signatures" in plots of response bandwidth versus wavelength of the peak sensitivity that allow for an acceptable estimate of the cone types whose signals mediate cell responses. 2. Averaged spectral bandwidths of color-opponent ganglion cells were compared with published data from color-selective neurons of subsequent levels of the geniculocortical pathway, including the extrastriate area termed V4. No significant differences were found between color-selective cells of the retina, dorsal lateral geniculate body, striate cortex, and V4. 3. The spectral location of the peak sensitivity of responses of the various types of color-opponent ganglion cells showed a relatively broad distribution, loosely clustering at some spectral loci. Comparison of such distribution with that of recently reported V4 cells response indicates that a remarkable scarcity of "blue/yellow" opponent responses in such reports. 4. In association with more recent electrophysiological studies of V4 cells, the results do not support current claims of a color specialization of this extrastriate area, and suggest lack of significant spectral tuning of the retinal output in, so far known, higher visual centers having color-selective cells.

Animals↗

Evaluation of nonradioactive, colored microspheres for measurement of regional myocardial blood flow in dogs.

Measurement of regional myocardial blood flow (RMBF) is crucial in experimental studies of myocardial ischemia and reperfusion in dogs. The standard measurement technique uses radioactive microspheres; however, not all institutions are able to dispose of radioactive waste and therefore cannot make use of this method. We tested a new, nonradioactive microsphere, labeled with colors instead of nuclides. Simultaneous blood flow measurements with two nuclide-labeled and two colored microspheres were performed after coronary occlusion in dogs. Both techniques show a within-method correlation of r greater than 0.98. Duplicate variability for paired RMBF values in 80 samples was 8.7 +/- 0.1% when computed with radioactive microspheres and 13.2 +/- 1.8% when computed with colored microspheres. There was a good correlation in the measurement of RMBF between the radioactive- and colored-microsphere methods (r = 0.98). The best-fitting linear regression line was expressed by the formula: Colored-microsphere RMBF = 1.11 (radioactive-microsphere RMBF)-0.02. When measured by colored microspheres, RMBF was approximately 8% higher than when computed with radioactive microspheres for blood flow values of 0-2 ml/min/g. When blood flow was increased pharmacologically to levels of 2-7.5 ml/min/g, colored microspheres yielded blood flow values 39% higher than the values computed by radioactive microspheres. We conclude that the nonradioactive, colored-microsphere method correlates with the radioactive technique, but at high flows, it yields values greater than those obtained with radioactive microspheres.

Animals↗

Depth information affects judgment of the surface-color mode appearance.

The mode of color appearance is determined not solely by physical properties of the stimulus but also by the conditions of surrounding stimuli. Coplanar ratio hypothesis suggests that the information provided in the same plane plays an important role in the judgment of lightness. We measured the upper-limit luminances of the test stimulus for the surface-color mode in a three-dimensionally represented environment to study the effects of depth and luminance conditions on the mode perception. The test stimulus and two array-type surrounding stimuli composed of 10 different colors were presented at different depths. The test stimulus was presented at three different depths. Subjects set the luminance of the test color to the point where it just ceased to appear in the complete surface-color mode. The upper-limit luminances of the test colors varied as the luminances of the surrounding stimulus displayed in the same depth changed. Our results indicate that the perception of the surface-color mode is mainly determined by the stimulus displayed in the same depth. These results support that belongingness--to which group in the environment the stimulus belongs--is important, and that the mode of color appearance is determined coplanar in a three-dimensional environment.

Color Perception↗

Ultrasonographic investigation of the Achilles tendon in elite badminton players using color Doppler.

BACKGROUND: The most frequent injuries in badminton players are in the lower extremities, especially in the Achilles tendon. HYPOTHESIS: The game of badminton may be related to abnormal intratendinous flow in the Achilles tendon as detected by color Doppler ultrasound. To a certain extent, this blood flow might be physiological, especially when examined after match. STUDY DESIGN: Cohort study (prevalence); Level of evidence, 3. METHODS: Seventy-two elite badminton players were interviewed regarding Achilles tendon pain (achillodynia) in the preceding 3 years. Color Doppler was used to examine the tendons of 64 players before their matches and 46 players after their matches. Intratendinous color Doppler flow was graded from 0 to 4. The Achilles tendon was divided into dominant (eg, right side for right-handed players and vice versa) and nondominant side and classified as midtendon, preinsertional, and calcaneal areas. RESULTS: Of 72 players, 26 had experienced achillodynia in 34 tendons, 18 on the dominant side and 16 on the nondominant side. In 62% of the players with achillodynia, the problems had begun slowly, and the median duration of symptoms was 4 months (range, 0-36 months). Thirty-five percent had ongoing pain in their tendons for a median duration of 12 months (range, 0-12 months). Achillodynia was not associated with the self-reported training load or with sex, age, weight, singles or doubles players, or racket side. Forty-six players were scanned before and after match. At baseline, color Doppler flow was present in the majority of players, and only 7 (16%) players had no color Doppler flow in either tendon. After match, all players had some color Doppler flow in 1 or both tendons. Achillodynia and color Doppler flow were related in the nondominant Achilles tendon (chi-square, P = .008). The grades of Doppler flow also increased significantly after match in the preinsertional area in both the nondominant (P = .0002) and dominant (P = .005) side tendons. CONCLUSION: A large proportion of the players had experienced achillodynia and habitually played with a degree of pain that demanded medication. The self-reported pain was associated with increased intratendinous color Doppler flow in the nondominant Achilles tendon. Doppler flow was found in most players before and in all players after the match and therefore may in part be a physiological response to activity.

Achilles Tendon↗

The color change in CO2 absorbents on drying: an in vitro study using moisture analysis.

UNLABELLED: Alkali hydroxide-free absorbents change color markedly when they dry, whereas absorbents containing alkali hydroxides do not. We investigated whether this observation can be explained by the weaker hygroscopic properties of pure calcium hydroxide compared with alkali hydroxides. Samples of the alkali hydroxide-free absorbents Amsorb or Superia and samples of these two absorbents with 1% or 3% NaOH or 3% KOH added were dried in a moisture analyzer at 105 degrees C to determine their moisture content and to assess the color of the samples during drying (each group, n = 5). Additionally, we repeated the experiments with pulverized samples of Baralyme and Spherasorb, which contain approximately 4% KOH and 1% NaOH, respectively. Amsorb and Superia changed color long before they were dry. After the addition of 1% NaOH, and as with the Spherasorb samples, the drying time required for a color change was longer, and the intensity of the resulting violet was less. This effect was even stronger when 3% NaOH was added. The samples with added KOH and the Baralyme did not change color at all on drying. We conclude that the differences in color change on drying in absorbents with varying NaOH or KOH content cannot be explained by larger water retention because of the hygroscopic properties of the alkali hydroxides. IMPLICATIONS: In an in vitro study, the moisture content and color change on drying were determined in samples of Amsorb or Superia and in the same absorbents with added NaOH or KOH. With increasing concentrations of alkali hydroxide, a delay in the color change upon drying was observed. However, the moisture content did not change.

Absorption↗

Evaluation of color discrimination in the white region.

Reference and test stimuli were produced on two separate color television screens to evaluate the color discrimination ability of the human eye for near-white colors. Each test stimulus had a luminance approximately equal to that of the reference, but was slightly different in chromaticity, e.g., [deltax] less than 0.01, [deltay] less than 0.01. The evaluation involved 20 persons observing 26 sets of color stimuli of 16-cd/m2 luminance, and 21 persons observing sets of color stimuli of 253 cd/m2. Observers were requested to categorize the color differences they perceived on a six-level rating scale. The results indicate that the differential thresholds for color difference of near-whites are between 4 and 8 CD (Color Difference), except in the bluish region.

Color Perception↗

Role of remote adaptation in perceived subjective color.

Light adaptation to illumination that is presented peripherally changes the subjective color of a central Benham disk stimulus. In our experiments we kept the peripheral illumination achromatic and remote (not even adjacent to the test stimulus). Using a high-frame-rate monitor, we produced the subjective color stimulus, to our knowledge for the first time, on a computer screen in emulation of the Benham disk programs. The resulting changes in the perceived subjective color were as follows: (1) Remote adapting illumination caused a dramatic shift in the perceived subjective color with a span from red to green; (2) there was a trade-off dependence between the area and the intensity of the remote adapting illumination with respect to the perceived color of the test stimulus; (3) the effect of the remote adaptation showed no interocular interaction. This finding suggests that the effect is elicited from a low-level stage in the visual pathway. In addition, we were able to approximate experimentally the spatial profile of the contribution of the remote illumination through the shift in the perceived color. We also found an opposite general trend of color shifts that occurred when either the central stimulus luminance or the remote illumination was increased. A suggested model for the reversed color shifts trend is discussed.

Adaptation, Ocular↗

Processing halftone color images by vector space methods.

The reproduction of color images by color halftoning can be characterized by the Neugebauer model/equation. However, the Neugebauer equation is not easy to solve because of the highly nonlinear relationship between the underlying Neugebauer primaries and the colorants. We attempt to solve the Neugebauer equation by vector space methods. The proposed method of solution is applicable to any number of colorants, although our experimental results are confined to the CMY and CMYK cases. Among the constraints we consider are those related to a bound on the permissible amount of total ink and a bound on the total cost of applying colorants to achieve a satisfactory level of color reproduction. Our results demonstrate that the vector space method is a feasible approach for solving for the required amounts of colorants in the constrained color halftoning problem.

Algorithms↗

Critical color differences determined with a visual search task.

Response times were measured for a visual search task in which the observer was required to find a target that differed from distracting stimuli only in color. In the first experiment the search time was measured as a function of display density for both small and large color differences. With small color differences response time increased with display density, indicating a serial search, but with large color differences response time was constant, indicating a parallel search. In the second experiment the color difference required for parallel search was measured in eight different directions from the distracter chromaticity. These color differences were much larger than threshold color differences and were not well represented by the ellipse used to describe the threshold contour around a point in color space.

Color Perception↗

Animal visual systems and the evolution of color patterns: sensory processing illuminates signal evolution.

Animal color pattern phenotypes evolve rapidly. What influences their evolution? Because color patterns are used in communication, selection for signal efficacy, relative to the intended receiver's visual system, may explain and predict the direction of evolution. We investigated this in bowerbirds, whose color patterns consist of plumage, bower structure, and ornaments and whose visual displays are presented under predictable visual conditions. We used data on avian vision, environmental conditions, color pattern properties, and an estimate of the bowerbird phylogeny to test hypotheses about evolutionary effects of visual processing. Different components of the color pattern evolve differently. Plumage sexual dimorphism increased and then decreased, while overall (plumage plus bower) visual contrast increased. The use of bowers allows relative crypsis of the bird but increased efficacy of the signal as a whole. Ornaments do not elaborate existing plumage features but instead are innovations (new color schemes) that increase signal efficacy. Isolation between species could be facilitated by plumage but not ornaments, because we observed character displacement only in plumage. Bowerbird color pattern evolution is at least partially predictable from the function of the visual system and from knowledge of different functions of different components of the color patterns. This provides clues to how more constrained visual signaling systems may evolve.

Animal Communication↗

The effect of color temperature of lighting sources on the autonomic nervous functions.

The present study was designed to investigate the effects of color temperature of lighting sources on the heart rate variability. Eight male students volunteered as subjects. The heart rate variability during task and rest sessions were estimated under nine different lighting environments consisting of three levels of color temperature (3000 degrees K, 5000 degrees K and 6700 degrees K) and three levels of illuminance (1001x, 3001x and 9001x). The lighting condition caused no effect on the mean heart rate. On the other hand, the power spectrum of heart rate was significantly influenced by the lighting conditions. The respiratory sinus arrhythmia component and Mayer wave related sinus arrhythmia component of the power spectrum increased under higher color temperature conditions. Judging from the consistency of heart rate level, the balance between the effects of parasympathetic and sympathetic nervous systems remained at a constant level irrespective of lighting quality and intensity. Therefore, both parasympathetic and sympathetic nervous functions were concluded to be enhanced under higher color temperature conditions. The light with higher color temperature was considered to activate the autonomic nervous function more than the light of lower color temperature. The effect of color temperature was much remarkable in the rest session comparing with the task session. This fact was discussed from the viewpoint of color temperature effect in environmental lighting.

Adult↗

Age-related changes of reaction time and p300 for low-contrast color stimuli: Effects of yellowing of the aging human lens.

We measured reaction time (RT), P300, and subjective evaluation for color Landolt-Cs with a gray color background presented on a CRT display. Seven young and 7 elderly subjects (mean ages: 21.6 and 68.4 years, respectively) participated, and the young subjects wore glasses with filters simulating spectral transmittance of an aging human lens as a test condition. The results for young subjects not wearing the filters showed that RT and P300 latency are constant among different test colors. In contrast, the results for elderly subjects showed that RT and P300 varied substantially depending upon the test colors and RT and P300 latency became longer than those of young subjects, particularly for gray and blue stimuli. In addition, the results for the young subjects with filters showed tendencies similar to those in elderly subjects. These results indicate that the yellowing of the human lens strongly influences reaction time and cognition time for color targets, suggesting that wearing the filters enables the young to simulate RT qualitatively as well as visibility of the elderly because both the simulated filter and the aging human lens modify the effective luminance, effective luminance contrast and effective color difference between the color target and the background on the retina. We also found that the reciprocal of RT and P300 latency could be expressed in a multiple regression model consisting of effective luminance, effective luminance contrast, effective color difference and age. Absolute values of RT and P300 latency in young subjects with filters, however, did not quantitatively coincide with those of the elderly subjects. There were differences of RT and P300 latency between the young with filters and the elderly, indicating that higher order age-related delay could be involved.

Adult↗

[Study on color stability of composite resins for a facing crown polymerized with high output photo-curing unit].

PURPOSE: This study investigated the color stability of composite resins for a facing crown cured with a high output photo-curing unit (Hyper LII, YAMAHACHI DENTAL MFG., CO.). METHODS: Four brands of composite resins for a facing crown after polymerization with Hyper LII were immersed in coffee. Color measurement was carried out before and 1, 2, and 4 weeks after immersion, and the results were compared. RESULTS: 1. After immersion in coffee, the L* values decreased gradually, the a* values showed little change, and the b* values increased gradually in all resins. 2. The difference in the color difference values (deltaE*ab) between each material became greater with time; the deltaE*ab after 4 weeks immersion were from 3.0 [Dentacolor (DEC), dentin specimen] to 6.3 [Solidex (SOL), enamel specimen] on polished surfaces, and from 0.9 [Gradia (GRA), dentin specimen] to 5.2 (SOL, enamel specimen) on non-polished surfaces. However, the deltaE*ab were 1/3 to 1/5 better than those of our previous studies. 3. The enamel specimens showed larger color differences than the dentin specimens. 4. When polished surfaces were compared with non-polished surfaces, Cesead II (CEII), DEC and SOL showed almost equal color differences while GRA showed larger color differences. CONCLUSIONS: This study suggests that composite resins for a facing crown cured with a high output photo-curing unit result in a decrease of color changes with time and an improvement of color stability.

Acrylic Resins↗

Diagnosis of appendiceal abscess in children with acute appendicitis: value of color Doppler sonography.

OBJECTIVE: We performed color Doppler imaging of the right lower quadrant in children with acute appendicitis to characterize the imaging findings indicative of appendiceal perforation and to determine the value of this technique in diagnosing appendiceal abscesses. SUBJECTS AND METHODS: Forty-seven children with surgically proven appendicitis underwent color Doppler sonography of the right lower quadrant as an adjunct to gray-scale sonography. At pathologic examination, 27 patients had nonperforating appendicitis and 20 patients had perforating appendicitis. In the latter group, seven patients had abscesses and 10 had phlegmon. The color Doppler sonograms were evaluated for the presence or absence of appendiceal hyperemia, hyperemic periappendiceal or pelvic fluid collections, and hyperemic soft tissues in the right lower quadrant. RESULTS: Color Doppler sonography showed appendiceal hyperemia in 21 (78%) of the 27 patients with nonperforating appendicitis and in eight (40%) of the 20 patients with perforating appendicitis. The hyperemia was scattered in 14 (67%) of the 21 patients without perforation and in six (75%) of the eight patients with perforation. The remaining patients with blood flow identifiable on color Doppler sonography had focal appendiceal hyperemia. For seven (35%) of the 20 patients with perforating appendicitis, color Doppler examination showed hyperemic, loculated periappendiceal or pelvic fluid collections, subsequently proved to be abscesses at surgery. No patient with nonperforating appendicitis had a hyperemic, loculated periappendiceal or pelvic fluid collection. Ten patients with perforating appendicitis displayed increased color Doppler signal in the adjacent right-lower-quadrant bowel loops and soft tissues, indicating phlegmon or peritonitis. CONCLUSION: Our results indicate that the best color Doppler sonographic predictors of appendiceal perforation are a hyperemic periappendiceal or pelvic fluid collection and periappendiceal soft-tissue hyperemia. A hyperemic, loculated fluid collection appears specific for the diagnosis of abscess.

Abdominal Abscess↗