study evaluated the effect of adding calcium or fuoride to 35% hydrogen
peroxide (HP) bleaching gel and the effect of human saliva on the
microhardness of sound and demineralized enamel, using an in situ model.
MATERIALS AND METHODS:
bovine enamel specimens (3 × 2 mm) were divided into two groups (n =
30): sound enamel (SE) and demineralized enamel (DE). Each group was
divided into three subgroups, according to the bleaching gel: 35% HP;
35% HP + calcium; 35% HP + fuoride. After bleaching therapy, the
specimens were fxed to intraoral devices worn by 10 volunteers for 7
days. Surface enamel microhardness (SMH) was measured before and after
bleaching procedures, and after 1 and 7 days of saliva exposure. Data
were analyzed by Repeated Measures ANOVA (5%).
variable time resulted in signifcant differences for SE and DE groups
(p = 0.001). For SE, signifcantly lower SMH was detected for control at
post-bleaching period in comparison to the baseline and after 7 days.
For DE, the lowest mean values were obtained before bleaching, and the
addition of calcium to the peroxide signifcantly increased enamel SMH.
The exposure to human saliva resulted in increased SMH.
addition of potential remineralizing agents into bleaching gels might
play an important role in maintaining the microhardness of sound enamel
and in inducing remineralization of artifcially demineralized enamel
right after bleaching, and the remineralizing action of human saliva
might minimize the deleterious effects of bleaching gels on enamel.
Clinical signifcance: The incorporation of calcium into HP bleaching gel
might be benefcial for the initial phases of the bleaching procedure.