title: Allocation of color space for different age groups using three-dimensional shade guide systems.
abstract: OBJECTIVE
  To determine the color space and the coverage error of two manual shade guide systems in four age groups of a selected population.
  
  
  METHODS
  A total of 174 patients were divided into four age groups and the shade of their natural teeth was measured (2067 teeth) with a spectrophotometer (Vita Easyshade). Color parameters in terms of L*, a*, b* values, chroma, and hue were recorded for each tooth. Color difference (ΔE*min) between each natural tooth and the closest match using two manual shade guide systems were calculated (3D Master shade guide standard and 3D Master shade guide with intermediate values). A Wilcoxon test was used to assess statistical differences between mean ΔE*min values for each system (α = 0.05).
  
  
  RESULTS
  The recoded ΔE of the two tested manual systems was 6.19 for 3D Master shade guide (standard) and 6.02 for 3D Master shade guide (intermediate values). A statistically significant difference (P < 0.001) was found between the mean ΔE*min of the two systems. 47% of natural teeth presented a best match with intermediate value and chroma shade tabs. The mean ΔE*min was influenced by the age group of the patients (5.15, 5.23, 6.58, and 6.69, respectively).
  
  
  CONCLUSIONS
  Using intermediate value and chroma did not improve shade match, nor the coverage error of the tested population. Nevertheless, better coverage error was observed in younger age groups compared to older anterior teeth.
authors.affiliation: Prosthodontic Department, Dental School, Saint Joseph University, Beirut, Lebanon. helene.haddad@usj.edu.lb
authors.forename: Helene J
authors.initials: HJ
authors.lastname: Haddad
authors.forename: Ziad
authors.initials: Z
authors.lastname: Salameh
authors.forename: Walid
authors.initials: W
authors.lastname: Sadig
authors.forename: Moustafa
authors.initials: M
authors.lastname: Aboushelib
authors.forename: Holger A
authors.initials: HA
authors.lastname: Jakstat
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D003116:Color; D017267:Dental Prosthesis Design / Q000295:instrumentation* / Q000592:standards; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D017797:Prosthesis Coloring / Q000295:instrumentation* / Q000592:standards; D013053:Spectrophotometry; D014070:Tooth / Q000033:anatomy & histology*; D055815:Young Adult