There were no statistically signifi

There were no statistically significant differences observed with or without the use of curing light in rela- tion to color change after the bleaching treatment. The use of activator sources (Halogen Light, LED and LED/Laser) for the purpose of accelerating the process of the bleaching gel and getting better results was not confirmed clinically.
Color stability was observed up to the sixth month
after treatment. There was a slight color relapse after six months, but there were no statistically significant differences between the groups (Figures 5 and 6). However, a prolonged clinical study observed color descent to the original tooth shade.34 Rosenstiel and
others36 monitored, in vitro, the color modification and
its stability after one session of in-office bleaching with
35% HP activated with light for 30 minutes. That study observed a color relapse seven days after treatment, which differed from the current study. This discrepancy might be due to the lower number of bleaching sessions,
the duration of the bleaching gel application being an in
vitro study and the introduction of new bleaching
agents and techniques. The inclusion of light-cured gin-
gival dams, chemical activators and the use of com- pounds that decrease tooth sensitivity have simplified
treatment and demonstrated better results.24
To promote better color stability, the use of both in-
office and at-home treatments has been recommended. This claim was not evaluated in the current study. With that method, the first bleaching session is done using 35% HP (in-office), followed by at-home bleaching.37 This combination of bleaching treatments for vital teeth provides better results, because it reduces the length of treatment and lowers irritation of the gingival tissues and tooth sensitivity.24 Another method for achieving better results is by using two application sessions (35% HP and three applications of the bleaching gel for each session, as was utilized in the current study.
The groups (G1, G2, G3, G4) were bleached in two clinical sessions, with a seven-day break between each session. Each session utilized a bleaching gel applica- tion lasting 45 minutes, totaling 90 minutes for the entire treatment to promote higher shade alteration and color stability.
The recorded tooth sensitivity was similar in both the
number of patients and intensity. Sensitivity is strong- ly related to concentration, time and rate of usage of the
bleaching gel.22,24,38
Tooth sensitivity probably occurred due to a high con-
centration of the bleaching gel and the length of appli- cation (35% HP, 45 minutes). Another factor that con- tributed to the increase in tooth sensitivity during the in-office bleaching treatment was the use of light and heat sources, which led to higher pulpal temperature.3
Tooth sensitivity occurred immediately following
bleaching, but a higher degree of sensitivity was record- ed after the second bleaching session, independent of the group evaluated. Tooth sensitivity that occurred immediately following bleaching was probably due to the high concentration of peroxide associated with a light source, increasing tooth temperature and the
patient's sensitivity.33
A recent study observed that the bleaching treatment
caused a therapeutic effect combined with an increase or decrease in oral bleeding and dental plaque and healthier gingival tissues, because certain hydrogen peroxide byproducts are antibacterial.39 A low concen- tration of bleaching agent in contact with gingival tis- sues causes no noticeable clinical lesion. Local inflam- mation can occur in gingival tissues that are exposed to high concentrations of peroxide, but that inflammation
is easily treated.39
In the current study, patients reported low gingival
irritation probably because it was possible to safely con- trol contact of the bleaching gel with the gingival mar- gin by using light-cured gingival dams.

CONCLUSIONS
1. The in-office bleaching agent used was effective
for the whitening of vital teeth.
2. The in-office bleaching treatment of vital teeth
with 35% hydrogen peroxide did not show improvement with the use of any auxiliary sources tested (halogen light, LED, LED/Laser).
3. There were no color stability differences up until
the sixth month after the evaluation between the study groups.