Objective To evaluate the clinical efficacy of a combined in- office cold light bleaching and nightguard vital bleaching（NGVB） system for treating tetracycline stained teeth（TST）. Methods 90 patients with light, medium and heavy TST were randomly and evenly divided into 3 groups. 30 patients with 472 TST from the treatment group were treated with in - office cold light bleaching and NGVB, 30 patients with 466 TST from the control group 1 were treated with in- office cold light bleaching and 30 patients with 469 TST from control group 2 were treated with NGVB. At the time of treatment completion, after half a year and after one year, Vitalescence esthetic restorative masters shade guide was used to record the change of color. Bleaching efficacy and course of treatment were calculated, and lightening stability were evaluated. Results 1）Three groups had satisfied lightening efficacy for light TST with 100% bleaching efficacy. The overall efficacy of treatment group and control group 2 were superior to the in- office cold light bleaching system（P0.05）, the periods of treatment of the treatment group for light, medium and heavy TST were shortened by 43%, 46% and 49%, respectively, compared to the control group 2. 2）All three groups′treatment efficacy for light, medium and heavy TST became weaker progressively （P0.05）. Both treatment group and control group 2 had better performance in treatment stability than control group 1. Conclusion In treating the light and medium tetracycline stained teeth, the combined in- office cold light bleaching and NGVB system can achieve a more satisfied whitening result in much shorter period, and significantly enhance the long term whitening stability.
