Time dependent influence of stain exposure following power bleaching

Freshly bleached teeth may be most susceptible to staining immediately following bleaching. Objective: The purpose of this study was to determine the influence of time on color and lightness following power bleaching and stain exposure. Method: Sixty extracted human teeth were randomly assigned to six experimental time groups (0 min, 2 hrs, 6 hrs, 12 hrs, 24 hrs, and 48 hrs.). Specimens were bleached using 38% hydrogen peroxide (Opalescence Boost, Ultradent) for three, 15 minute cycles for a total of 45 minutes.  After the elapsed time prescribed for each group, the bleached teeth were further divided into one of two chromogenic subgroups and immersed in coffee or grape juice for 1 hour. Custom clear silicone molds were fabricated to hold specimens during color measurement to allow for controlled repeat measurements before and after staining using the Vita EasyShade intraoral spectrophotometer (Vident).  Data was analyzed by an ANOVA and LSD post hoc test at the 0.5 level of significance.

Results: Means for color change (DE) and lightness (DL) of bleached teeth after elapsed time prior to exposure to stain are listed in the table.

 

Chromogenic Agent	Color Parameter	0 Hr	2 Hr	6 Hr	12 Hr	24 Hr	48 Hr
Grape	DL	-2.8	-4.2	-4.6	2.6	0.3	2.5
	DE	5.8	6.3	5.2	7.6	7.4	10
Coffee	DL	-2.3	-1.2	-3.4	0.4	4.9	7.1
	DE	3.5†	3.1†	4.2†	4.6	6.9	7.9
† p<0.05

There was no significant difference in color change of bleached teeth after exposure to grape juice, p=0.527, however DE was significant for coffee, p=0.47 at or before 6 hours.  DL values were negative (darker) at or before 6 hours following bleaching for both chromogenic agents. Conclusion:  The results of this study suggest waiting a minimum of 6 hours after power bleaching prior to exposure to chromogenic agents.