Table 1. Means of pH value according to group and time, of application.

Bleaching agent	Time
	Baseline	Half of application time *	End of application time**
CP	6.6	6.7	6.7
CPN	6.6	6.7	6.6
HP	7.0	7.2	7.3
HPN	7.3	7.4	7.3

* CP and CPN groups: 30 minutes; HP and HPN groups: 20 minutes.

** CP and CPN groups: 1 hour; HP and HPN groups: 40 minutes.