title: Effect of dehydration time on tooth colour measurement in vitro.
abstract: OBJECTIVE
  To investigate the effect of dehydration time on tooth colour measurement in vitro using colourimetry.
  
  
  METHODS
  Ten extracted human maxillary central incisors were used. L*a*b* values at the centre of the labial surface of each tooth were measured using a colourimeter. The first measurement was performed after removal of excess water. The second and third measurements were performed after the teeth had dried at room temperature for 2 h and 4 h, respectively. The colour differences (ΔE) between dehydration time points were calculated. Repeated oneway ANOVA was performed for colour values at different dehydration time points. Pairwise comparison of group means (Student t test) was used to examine the differences between ΔE and 1.5ΔE (α = 0.05).
  
  
  RESULTS
  There were statistically significant changes in the L* values after 2 h and 4 h dehydration as well as between each ΔE and 1.5ΔE. Neither 2 h nor 4h dehydration resulted in change of a* value or b* value.
  
  
  CONCLUSIONS
  Dehydration time affected colour measurement using a colourimeter; the teeth become lighter after dehydration for 2 h or longer.
authors.affiliation: Wenzhou Medical Collleg, Wenhou, People's Republic of China.
authors.forename: Ruo Xi
authors.initials: RX
authors.lastname: Du
authors.forename: Yi Ming
authors.initials: YM
authors.lastname: Li
authors.forename: Jian Feng
authors.initials: JF
authors.lastname: Ma
mesh_terms: D000704:Analysis of Variance; D003116:Color; D003681:Dehydration; D006801:Humans; D066298:In Vitro Techniques; D007180:Incisor