Influence of Bleaching and Aging Procedures on Color and Whiteness of Dental Composites.

Bleaching can cause perceptible color changes on resin-based composite (RBC) restorations that may not be stable with aging. The objective of this study was to evaluate color stability and whiteness variations of RBCs after bleaching and aging procedures. Discs (10 mm in diameter and 1 mm thick) of shades A2 and A3 were fabricated from two RBCs (Filtek Z250 and Filtek Z350 XT) and divided into three subgroups (for each composite and shade) (n=5) as follows: control (no bleaching), at-home bleaching, and in-office bleaching. All specimens underwent an accelerated artificial aging up to 450 KJ/m2 and 900 KJ/m2 in an aging chamber (Suntest XXL+). A spectroradiometer (SpectraScan PR-670) was used to obtain CIE L*a*b* coordinates. CIEDE2000 color difference (ΔE00) and whiteness index for dentistry (WID) were used to evaluate color stability. Color and whiteness differences data were analyzed considering the 50:50% visual color difference thresholds (perceptibility [PT] and acceptability [AT]) and 50:50% whiteness thresholds (whiteness perceptibility [WPT] and whiteness acceptability [WAT]). Analysis of variance and Tukey tests (α=0.05) were used to statistically analyze the data. After bleaching, all specimens showed ΔE00 and ΔWID values below their corresponding acceptability thresholds (AT and WAT, respectively). After aging, L* and WID values decreased while b* values increased (p≤0.05), resulting in ΔE00 and ΔWID values above AT and WAT, respectively. Color changes after bleaching RBCs were clinically acceptable, while aging provoked clinically perceptible color changes.

Development of a model shade guide for primary teeth.

AIM: Large disparities in colour ranges and distribution between primary and permanent teeth make shade guides for permanent teeth unsuitable for primary teeth applications. The aim of the study was to develop a model shade guide for primary teeth. STUDY DESIGN: The Vita Easyshade intraoral spectrophotometer was used to determine colour at the middle labial/buccal third surface of 612 primary teeth of 102 patients. METHODS: Model shade guides, containing 1-16 tabs, were designed in CIELAB (DeltaE*) and CIEDE2000 (DeltaE') colour difference formulae using nonlinear optimization. The coverage error (DeltaECOV) was calculated as the mean of minimal colour differences between each of primary teeth and the "closest" shade tab. Results were analyzed using descriptive and analytical statistics. RESULTS: The coverage error of Vitapan Classical shade guide applied to the primary teeth evaluated was 4.2 (SD +/- 1.8). DeltaE*COV and DeltaE'COV values for model shade guides with 16 tabs were 1.8 and 1.3, respectively. The CIELAB coverage error of the model shade guide containing two tabs outperformed DeltaE*COV of Vitapan Classical. CONCLUSIONS: As compared with Vitapan Classical shade guide, significantly smaller coverage error was obtained in the model shade guide with the same number of tabs, designed via constrained nonlinear optimization.

Color adjustment potential of resin composites.

The study objective was to explore a new method for quantifying the color adjustment potential originating from physical translucency on a set of 7 resin composites, and then for testing the hypothesis that color adjustment potential is dependent on the composites and shades studied. Two-composite specimens (an outer base shade with an inner hole filled with inner test shades) and single-composite specimens of all shades were made. A 1-mm circular area, with its center in the middle of the specimen (P0mm), was measured by means of spectroradiometry. A newly developed equation for quantification of the color adjustment potential was tested. Color adjustment potential at P0mm ranged from -0.19 (negative color adjustment/contrast) to 0.61. Within the limitations of this study, a newly developed concept and equation have proved the existence of the physical component of color adjustment of translucent dental materials. Color adjustment potential was dependent on composite and shade.

Dental color standards: shade tab arrangement.

PURPOSE: The aim of this study was to analyze the shade tab arrangement of two popular dental shade guides, suggest possible improvements, and propose clinical guidelines. MATERIALS AND METHODS: Data were recorded using a colorimeter set to standard illuminant source C and CIE L*a*b* system. The manufacturers' shade tab arrangement as well as the possible improvements in the arrangement of shade tabs of Vitapan Classical and Vitapan 3-D Master (Vita Zahnfabrik, Bad Säckingen, Germany) shade guides were examined by regression analysis. RESULTS: Certain shortcomings in the manufacturers' arrangement of both color standards were observed. The Vitapan 3-D Master arrangement was more consistent, but with a decrease in lightness, tab saturation decreased as well in four of its five groups. When Vitapan Classical and Vitapan 3-D Master tabs were arranged according to deltaE* in relation to the lightest tab, r2 was 0.98 and 0.96, respectively. After dividing the total deltaE* range into four equal segments for the newly established Vitapan Classical guide, r2 was 0.91, 0.95, 0.68, and 0.94, respectively. Corresponding r2 values for Vitapan 3-D Master were 0.96, 0.94, 0.90, 0.94, and 1.0. CLINICAL SIGNIFICANCE: Total color difference in relation to the lightest tab, followed by the tab division into an adequate number of groups, is recommended as a possible and universally applicable mode of tab arrangement in dental color standards.