Effect of dehydration time on tooth colour measurement in vitro.

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. CONCLUSION Dehydration time affected colour measurement using a colourimeter; the teeth become lighter after dehydration for 2 h or longer.