Effect of pH of In-Office Bleaching Gels and Timing of Fluoride Gel Application on Microhardness and Surface Morphology of Enamel

Table 1

Summary of the experimental conditions.

Groups	Treatments
1	Unbleached specimens (negative control)
2	2% neutral sodium fluoride gel^c (2% NaF) (positive control)
3	35% Hydrogen peroxide (HP)^a
4	37.5% HP^b
5	35% hydrogen peroxide (HP)^a +2% NaF at each session for 4 min
6	2% NaF^c for 4 min 24 hr before bleaching treatment +35% HP^a
7	37.5% HP^a +2% NaF at each session for 4 min
8	2% NaF for 4 min 24 hr before bleaching treatment +37.5% HP^b

^aPola Office 35% HP (SDI, Bayswater, Victoria, Australia), ^bPola Office +37.5% HP (SDI, Bayswater, Victoria, Australia); ^cFluor Gel (Maquira Dental Products, Maringá, PR, Brazil).