title: Repeatability in Color Measurements of a Spectrophotometer using Different Positioning Devices.
abstract: This study aimed to evaluate the repeatability of color measurements of an intraoral spectrophotometer with the use of three different methods by two operators.
  
  
  
  A total of 60 teeth were obtained, comprising 30 human maxillary teeth [central incisors (n = 10); canines (n = 10); molars (n = 10)] and 30 artificial teeth [lateral incisors (n = 10); premolar (n = 20)]. Multiple repeated color measurements were obtained from each tooth using three measuring methods by each of the two operators. Five typodonts with alternating artificial and human teeth were made. Measurements were taken by two operators with the Vita EasyShade spectrophotometer using the custom tray (CT), custom jig (CJ) and free hand (FH) method, twice, at an interval of 2 to 7 days. Friedman test was used to detect difference among the three color measuring methods. Post hoc Wilcoxon signed-rank test with Bonferroni correction applied was used for pair-wise comparison of color measurements among the three methods. Additionally, a paired-sample t-test was used to assess a significant difference between the two duplicated measurements made on the same tooth by the same operator for each color parameter and measuring method.
  
  
  
  For operator A, mean (SD) overall color change-ΔE* (SD) perceived for FH, CT and CJ were 2.21(2.00), 2.39 (1.58) and 2.86 (1.92), respectively. There was statistically significant difference in perceived ΔE* in FH vs CJ (p = 0.0107). However, there were no significant differences between FH and CT (p = 0.2829) or between CT and CJ (p = 0.1159). For operator B mean ΔE* (SD) for FH, CT and CJ were 3.24 (3.46), 1.95 (1.19) and 2.45 (1.56), respectively. There was a significant difference between FH and CT (p = 0.0031). However, there were no statistically significant differences in ΔE* in FH vs CJ (p = 0.3696) or CT vs CJ (p = 0.0809).
  
  
  
  The repeatability of color measurements was different among the three measuring methods by operators. Overall, the CT method worked well for both operators.
  
  
  
  The use of a custom tray with apertures can improve the repeatability of color measurements of an intraoral spectrophotometer.
authors.affiliation: Department of Dentistry, University of Iowa, College of Dentistry, Iowa City, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Hemming
authors.affiliation: Associate Professor, Department of Center for Dental Research, Loma Linda University, School of Dentistry, 11175 Campus Street Suite A 1010, Loma Linda-92350 California, USA, Phone: 909 558 8069, e-mail: sorankwon@llu.edu.
authors.forename: So Ran
authors.initials: SR
authors.lastname: Kwon
authors.affiliation: Department of Preventive and Community Dentistry and Division of Biostatistics and Research Design, University of Iowa, College of Dentistry, Iowa City, USA.
authors.forename: Fang
authors.initials: F
authors.lastname: Qian
mesh_terms: D003116:Color; D006801:Humans; D017797:Prosthesis Coloring; D013053:Spectrophotometry; D014070:Tooth; D014093:Tooth, Artificial
keywords: Custom jig; Custom tray with apertures; Tooth color measurements; Tooth whitening