Department of Orthodontics, School of Dentistry, Orthodontic Research Center, Shiraz University of Medical Sciences, Shiraz, Iran.
Department of Prosthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran.
Am J Orthod Dentofacial Orthop. 2021 Jan;159(1):e35-e40. doi: 10.1016/j.ajodo.2020.08.013. Epub 2020 Nov 19.
This study aimed to assess the effect of changes in tooth torque on the perceived color of composite and porcelain restorations.
A total of 30 patients with previous composite restorations and 30 patients with porcelain restorations on lateral and central incisors were selected. To simulate the effect of dental torque change, we asked the patients to tilt their heads upwards and downwards to represent buccal and palatal crown torque, respectively. Photographs were taken in 3 different positions (natural head position, 15° upward tilt, and 15° downward tilt). A laser alignment tool was used to help with head positioning. Color was measured on the 3 principal axes of the Commission Internationale de L'Eclairage, L∗, a∗, and b∗ color space using Photoshop software (Adobe, San Jose, Calif), and color differences were calculated. The midpoint of the clinical crown, both mesiodistally and incisogingival, was selected as the point of measurement. A general linear model was used to analyze the significance of changes in each value of different tooth torques. A t test was used to compare color changes of 2 different incisors (central and lateral) and overall color differences in the 2 types of restoration.
Significant changes of the L∗ and a∗ values were found as a result of the change in head inclination, whereas b∗ values remained unchanged. It was found that buccal crown torque resulted in lighter and greener porcelain restorations. Composite restorations behaved similarly with the only difference being that the central incisors appeared bluer. Palatal crown torque resulted in a darker and redder porcelain restoration and a darker, redder, and yellower composite restoration. No significant differences were found between color changes in the central and lateral incisors. Furthermore, porcelain and composite restorations had similar color changes with alteration of head inclination.
Orthodontic changes of tooth torque alter the color perceived from composite and porcelain restorations.
本研究旨在评估牙扭矩变化对复合树脂和瓷修复体颜色感知的影响。
选择 30 例先前有复合树脂修复体的患者和 30 例有前牙颊舌向和腭向牙冠扭矩的瓷修复体患者。为了模拟牙扭矩变化的效果，我们让患者向上和向下倾斜头部，分别代表颊侧和腭侧牙冠扭矩。在 3 个不同位置（自然头位、向上倾斜 15°和向下倾斜 15°）拍摄照片。使用激光对准工具帮助定位头部。使用 Photoshop 软件（Adobe，圣何塞，加利福尼亚州）在国际照明委员会的 L*、a和 b颜色空间的 3 个主轴上测量颜色，并计算颜色差异。选择临床牙冠的中点，即近远中向和龈牙合向，作为测量点。使用一般线性模型分析不同牙扭矩变化的每个值的显著性。使用 t 检验比较 2 种不同切牙（中切牙和侧切牙）的颜色变化和 2 种修复体的总体颜色差异。
发现头部倾斜变化导致 L和 a值发生显著变化，而 b*值保持不变。结果发现颊侧牙冠扭矩导致瓷修复体更亮更绿。复合树脂修复体表现相似，唯一的区别是中切牙看起来更蓝。腭侧牙冠扭矩导致瓷修复体颜色更深更红，复合修复体颜色更深、更红、更黄。中切牙和侧切牙的颜色变化无显著差异。此外，随着头部倾斜的改变，牙扭矩的正畸变化会改变对复合树脂和瓷修复体的颜色感知。
牙扭矩的正畸变化会改变对复合树脂和瓷修复体颜色的感知。
