Determining color difference thresholds in denture base acrylic resin.
BACKGROUND
In restorative prostheses, color is important, but the choice of color difference formula used to quantify color change in acrylic resins is not straightforward.


OBJECTIVE
The purpose of this in vitro study was to choose a color difference formula that best represented differences between the calculated color and the observed imperceptible to unacceptable color and to determine the corresponding perceptibility and acceptability threshold of color stability for denture base acrylic resins.


METHODS
A total of 291 acrylic resin denture base plates were fabricated and subjected to radiation tests from zero to 42 hours in accordance with ISO 7491:2000. Color was measured with a portable spectrophotometer, and color differences were calculated with 3 International Commission on Illumination (CIE) formulas: CIELab, CMC(1:1), and CIEDE2000. Thirty-four observers with no deficiencies in color perception participated in psychophysical perceptibility and acceptability assessments under controlled conditions in vitro. These 2 types of assessments were regressed to each observer by each formula to generate receiver operator characteristic (ROC) curves. Areas under the curves (AUCs) were then calculated and analyzed to exclude observers with poor color discrimination. AUCs were subjected to 1-way ANOVA (α=.05) to deter the statistical significance of discriminability among the 3 formulas in terms of perceptibility and acceptability judgments. Student-Newman-Keuls tests (α=.05) were used for post hoc comparison.


RESULTS
CMC(1:1) and CIEDE2000 formulas performed better for imperceptible to unacceptable color differences, with corresponding CMC(1:1) and CIEDE2000 values for perceptibility of 2.52 and 1.72, respectively, and acceptability thresholds of 6.21 and 4.08, respectively.


CONCLUSIONS
Formulas CMC(1:1) and CIEDE2000 possess higher discriminability than that of CIELab in the assessment of perceptible color difference threshold of denture base acrylic resin. A statistically significant difference exists between perceptibility and acceptability thresholds for denture base acrylic resin.
Postgraduate student, Department of Dental Materials, School and Hospital of Stomatology, Peking University, Beijing, China.
Jiabao
J
Ren
Professor, Department of Dental Materials, School and Hospital of Stomatology, Peking University, Beijing, China.
Hong
H
Lin
Professor, National Laboratory of Color Science and Engineering, Beijing Institute of Technology, Beijing, China.
Qingmei
Q
Huang
Professor, Department of Dental Materials, School and Hospital of Stomatology, Peking University, Beijing, China. Electronic address: gangzheng101@yahoo.com.
Gang
G
Zheng
D000180:Acrylic Resins; D003116:Color; D003764:Dental Materials; D003819:Denture Bases; D006801:Humans; D010342:Patient Acceptance of Health Care; D010465:Perception; D017797:Prosthesis Coloring; D013053:Spectrophotometry
D000180:Acrylic Resins; D003764:Dental Materials