Color Stability Before and After In-Office Bleaching: Pilot Study

Objective: The aim of this pilot study is the evaluation and measurement of color stability from baseline until stabilization of color associated with bleaching and the dehydration and rehydration process of the teeth. 

Method: Six extracted intact human third molars were randomly selected, cleaned, and stored in artificial saliva at 37⁰C. A custom positioning jig was fabricated for each tooth for reproducible color measurement. A baseline shade was recorded according to the Commission Internationale de l'Eclairage L*a*b* (CIE-L*a*b*) using a Minolta Chromameter CR-(200).  Color measurement for all testing was taking at baseline, 15 min, 30 min, 2h, 12h and every 2 h thereafter until color stabilization occurred. Phase 1(dehydration-rehydration w/o bleaching): For dehydration, all teeth lightened and color stability occurred at 6 h. Rehydration of teeth to the baseline of color was achieved after 14 hours.  Phase 2 (Effect of bleaching): An in-office bleach material (Zoom 25% HP) was applied to each tooth according to the Kwon technique (polyethylene wrap placed to cover the gel) for one hour.  All comparisons were made to a Delta value of 2.6 (perceivable difference).

Result:  Phase 1: A mean ΔL* of -13.05(±15.62) was observed for tooth dehydration with no perceivable changes in chroma Δa* and Δb*.  Phase 2:  In-office bleaching produced dehydration and chroma changes when measured immediately after bleaching with a mean of ΔL* =-12.45(±2.4), Δa*=0.31(±0.53), and Δb*= 3.67(±1.76).  After rehydration of bleached teeth, luminosity values (ΔL*) returned to normal and only chromaticity changes (Δb*) were observed with a mean of 4.77(±1.91).   

Conclusion: Within the limits of this study, in-office bleaching produced dehydration and chroma changes, represented by ΔL* and Δb*.  Upon rehydration, the color changes were not as discernible. Further study will be conducted to determine the validity of these findings.