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PubMed2003

Shade matching.

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Color Perception↗
PubMed2003

Successful shade matching--what does it take?

Dental practitioners can avoid expensive and embarrassing shade matching errors by learning about the structure and function of the eye and how to control the external and internal factors that affect human vision. The color of objects is identified by the visible light that they reflect; objects can reflect only the light that shines upon them. Eyes sense the hue, intensity, and saturation of light, so lighting of proper intensity and color balance is necessary for consistent, correct shade-matching. Although sunlight is the most common standard for good lighting, in everyday practice, it cannot be used for shade matching because of its extreme variability with weather conditions, time of day, and season of the year. In addition to external factors such as lighting, conditions internal to the observer also play a role in accurate color perception. Color vision confusion (CVC), often called "color blindness," is a serious handicap for dental professionals. The popular assumption is that very few people are afflicted; in fact, all people suffer from some level of color vision confusion. This distortion of visual information can be permanent or transitory. Therefore, controlling these variables can lead to color matching success.

Color Perception↗
PubMed2004

[The choice of color in fixed prosthetics: what steps should be followed for a reliable outcome?].

The creation of a perfectly-matched esthetic fixed restoration is undeniably one of the most difficult challenges in modern dentistry. The final outcome depends on several essential steps: the use of an appropriate light source, the accurate analysis and correct evaluation of patient's teeth parameters (morphology, colour, surface texture,...), the clear and precise transmission of this data to the laboratory and the sound interpretation of it by a dental technician who masters esthetic prosthetic techniques perfectly. The purpose of this paper was to give a reproducible clinical method to the practitioner in order to achieve a reliable dental colorimetric analysis.

Color↗
PubMed2005

[Effect of thickness and shade of porcelain of ceramometal restorations on color of gingival porcelain].

OBJECTIVE: The purpose of this study was to evaluate the color changes of gingival porcelain through varying thickness and shade of porcelain of ceramometal restorations. METHODS: In this study a spectrophotometer (PR-650) was used for color analysis. The color changes of dentin porcelain and gingival porcelain with three varied thickness (0.3 mm, 0.6 mm and 0.9 mm) were investigated. In addition, the color variances of Shofu vintage porcelain shade A2, A3 and B2 were tested. RESULTS: The results showed that decreased L * value of ceramometal restorations and increased a * value were due to the increase of the gingival porcelain thickness, color measurements showed the same trend as the increased dentin porcelain thickness and the opaque and dentin porcelain with different color affected the appearance of gingival porcelain. CONCLUSION: The color of gingival porcelain would be changed with the differences of thickness and shade of porcelain of ceramometal restorations.

Color↗
PubMedDate not supplied

Shade selection for restorative dentistry.

There is no absolute single method that will work all of the time for every patient/dentist situation. Computerized systems offer great hope for the future but visual shade selection with the human eye still is the most predictable method available.

Color Perception↗
PubMed2006

The effect of colour defective vision on shade matching accuracy.

One hundred and forty one male dental students and staff were screened for colour-defective vision. Ten colour-defective and 20 non colour-defective subjects then carried out a shade matching exercise using nine selected shades and another matched, shade tab (to test for consistency) from Vita shade guides. All shade matching took place under standard lighting conditions. Each subject also completed a short questionnaire relevant to shade matching. There were no significant differences found between colour-defective and non colour-defective subjects in shade matching abilities. Although both subject groups were similar in their shade matching abilities, individuals with colour defective vision perceived it to be a slightly more difficult exercise.

Case-Control Studies↗
PubMedDate not supplied

Translucency parameter of colorants for maxillofacial prostheses.

The masking power of various generic, dry mineral earth, and flocking colorants dispersed in medical-grade silicone elastomer was investigated. Reflectance measurements were made by diffuse reflectance spectrophotometry using black and white backings. These data were reduced to optical scattering and absorption coefficients through the use of the Kubelka-Munk reflectance theory. The color difference between a 0.13-cm-thick layer of the colored elastomer placed on an ideal black backing and this layer on an ideal white backing was calculated and established as a translucency parameter. Using analysis of variance and stepwise comparison testing, significant differences were found among the translucency parameters of the colorants. Since these colorants differ substantially in their ability to mask underlying colors and since the translucency of maxillofacial material is an important aspect of color measurement and natural appearance, differences in these colorants go beyond their obvious differences in color.

Absorption↗
PubMedDate not supplied

Using a computer color-matching system in color reproduction of porcelain restorations. Part 3: A newly developed spectrophotometer designed for clinical application.

This paper reports the development of a newly modified, noncontact spectrophotometer for clinical use. The instrument is capable of accurately measuring the color within small areas (1 x 2 mm) of a tooth. This spectrophotometer used a 45 degree/0 degree geometry, a 150W halogen lamp, and fiberoptics to focus the light, together with a lens having a focal point distance of 85 mm. A movable platform was added to the apparatus to automatically scan and measure the color of specific areas. Short-term repeatability indicated the color difference delta E to be approximately 0.15.

Color↗
PubMedDate not supplied

The in vitro color stability of acrylic resins for provisional restorations.

This study made an in vitro comparative evaluation of the color variation of four types of acrylic resin for provisional fixed prostheses, as determined using computerized spectrophotometry, before and after a 20- and 30-day cycle of immersion in four staining solutions. The four acrylic resins used for provisional fixed restorations were: Cold Pac, Trim, Protemp, and Mixacryl II. Thirty-two specimens for each resin were divided into four subgroups of eight elements, immersed in the four staining solutions (synthetic saliva, synthetic saliva and tea, synthetic saliva and coffee, and synthetic saliva and chlorhexidine in 0.12% water solution), and then placed into four thermostatic baths at 37 degrees C +/- 1 degree C. All specimens were measured for each resin before immersion (baseline). After 20 and 30 days, the specimens were analyzed by computerized spectrophotometry and compared. All data were analyzed with analysis of variance for repeated measures (P < .05). Only the Cold Pac resin was color stable in all staining solutions, while the others showed color changes from the different staining solutions.

Acrylic Resins↗
PubMed2006

Effect of core and veneer thicknesses on the color parameters of two all-ceramic systems.

STATEMENT OF PROBLEM: Specific contributions of the core and the veneer thickness on the appearance of layered disk specimens are not well characterized. PURPOSE: This study examined the effect of varying core and veneer thickness on the color parameters of layered disk specimens made of 2 ceramic systems. MATERIAL AND METHODS: Disk specimens 16 mm in diameter with core/veneer thickness (mm) of 0.8/0.2 (baseline), 0.8/0.7, 0.8/1.2, 1.0/0.5, 1.3/0.2, and 1.8/0.2 were made from a leucite-reinforced ceramic (IPS Empress; 2B shade), and thickness (mm) of 0.5/0.5 (baseline), 0.5/1.0, 0.5/1.5, 0.8/0.7, 1.0/0.5, and 1.5/0.5 were made from a glass-infiltrated spinell ceramic (In-Ceram Spinell; A2 shade). Color parameters L*, a*, and b* of CIELAB color space were measured against a neutral gray background with a tri-stimulus colorimeter, and deltaE between disk group and its respective baseline group was calculated. Analysis of variance was used to determine the effect of material and core and veneer thickness on the color parameters (alpha = .05). RESULTS: Increasing the total disk thickness resulted in decrease of L* (P < .001) and an increase of a* (P < .001), b* (P < .001), and deltaE (P = .0236). For leucite-reinforced ceramic, the core thickness, veneer thickness, and their interaction exhibited significant influence on the mean values of a* and b* (P < .0028) but not on the mean values of L*. For spinell ceramic, the core thickness and veneer thickness exhibited significant influence on the mean values of L* and b* (P < .0272) but not on a*; the interaction demonstrated significant influence on b* (P = .0003) but not on L* and a*. CONCLUSION: The color appearance of the layered ceramic disk specimens is strongly influenced not only by the core thickness and veneer thickness, but also by their interaction.

Aluminum Oxide↗