Translucency and color match with a shade guide of esthetic brackets with the aid of a spectroradiometer

ABSTRACT Objective: Since the color of esthetic brackets should match that of teeth, the aims of this study were to determine the color and translucency of esthetic brackets by means of the clinically relevant use of a spectroradiometer, and to compare the color of brackets with that of a commercial shade guide. Methods: The color of central and tie-wing regions of four plastic and four ceramic brackets was measured according to the CIE L*a*b* color scale over white and black backgrounds. Brackets were classified into five groups based on their composition. The color of Vitapan Classical Shade Guide tabs was also measured. Translucency parameter (TP) and contrast ratio (CR) were calculated to determine translucency. Results: Color differences between brackets and the shade guide tabs were 10.4 - 34.5 ∆E*ab units. TP and CR values for the central region were 16.4 - 27.7 and 0.38 - 0.58, whereas for the tie-wings they were 24.0 - 39.9 and 0.25 - 0.45, respectively. The color coordinates, TP and CR values were significantly influenced by bracket composition and brand (p < 0.05). Conclusions: Esthetic brackets investigated herein showed unacceptable color differences (∆E*ab > 5.5) compared with the shade guide tabs. Differences in the translucency of brackets by brand were within the visually perceptible range (∆CR > 0.07). Therefore, brackets showing the best matching performance for each case should be selected considering esthetic and functional demands.

摘要
目的：由于美学托槽（esthetic brackets）的颜色需与天然牙色泽匹配，本研究旨在采用符合临床应用要求的分光辐射度计（spectroradiometer），测定美学托槽的颜色与半透明性，并将托槽颜色与商用比色板进行对比。
方法：依据CIE L*a*b*色彩空间（CIE L*a*b* color scale），在白色与黑色背景下，测量4枚塑料托槽与4枚陶瓷托槽的中心区及结扎翼区（tie-wing regions）的颜色。按材质将托槽分为5组。同时测定维他瓷经典比色板（Vitapan Classical Shade Guide）色片的颜色。通过计算半透明参数（translucency parameter, TP）与对比度比（contrast ratio, CR）来评估半透明性。
结果：托槽与比色板色片的色差值为10.4~34.5 ∆E*ab单位。中心区的TP与CR值分别为16.4~27.7及0.38~0.58，结扎翼区则分别为24.0~39.9及0.25~0.45。托槽的颜色坐标、TP及CR值均受托槽材质与品牌的显著影响（p<0.05）。
结论：本研究所测试的美学托槽与比色板色片相比，色差值均超出临床可接受范围（∆E*ab>5.5）。不同品牌托槽的半透明性差异处于视觉可感知区间内（∆CR>0.07）。因此，临床应结合美学与功能需求，选择适配各病例的最佳匹配托槽。