Nightguard vital bleaching is a widely used technique because of its easy application and low cost. However, questions about its effectiveness, longevity and effect on oral tissues have been raised.

Objective: This independent randomized controlled clinical trial evaluated the effectiveness and side effects of nightguard vital bleaching with 10% carbamide peroxide with the criteria set out in the American Dental Association's clinical guidelines.

Materials and Methods: Fifty young volunteers were randomly allocated to either an experimental group (Opalescence PF 10%, pH 6.5 [OPA group]) or a control group (placebo, pH 7.0 [PLA group]). Each volunteer used the group-appropriate gel in a tray every night (an overnight bleaching or placebo treatment for 6 to 8 hours) for 21 days. Observation periods were baseline, immediately after 3 weeks of use (day 21), and 30 days (day 30) and 6 months (day 180 — only for the OPA group) after finishing the treatment.

The 4 variables studied were tooth colour, gingival bleeding, tooth sensitivity and volunteers' satisfaction with the final colour of their teeth. The calibrated examiner analyzed tooth colour at each observation period using the Vitapan classical shade guide (Vita Zahnfabrik, Bad Sackingen, Germany) to classify the colour of each volunteer's upper incisors, in descending order of colour value, from light to dark, according to the manufacturer's specifications. Gingival bleeding was assessed at day 21 and categorized as present or absent, according to the gingival bleeding index modified by Lang. Tooth sensitivity occurring during treatment was categorized as yes or no by the volunteers and recorded in their diaries. Volunteers' satisfaction with the final colour of their teeth was categorized as satisfactory or nonsatisfactory.

One evaluator did all the analyses. The colour values for each group at each observation time were analyzed with Friedman's test. Data on tooth sensitivity, gingival bleeding and volunteers' satisfaction were analyzed with Fisher's exact test. All statistical testing was done at a significance level of 5%. In addition, a descriptive analysis of the score frequencies was done to evaluate the reduction in colour values for the Vitapan classical shade guide.

Results: At baseline, the median colour of the upper incisors was 5 (A2) and no gingival bleeding or tooth sensitivity was observed for any volunteer. The overall bleaching success for the OPA group was 96% for all observation periods. The median increase in the lightness of the teeth in the OPA group was 3 units, as assessed with the Vitapan classical shade guide (from A2 to A1); 88% maintained this improvement in lightness for 6 months. In the PLA group, 8% had a 2-unit reduction in tooth colour at day 21. Volunteers' satisfaction with the bleaching effect was significantly related to the group to which they belonged (p < 0.001): the satisfaction of the OPA group was 92%; that of the PLA group, 8%. Tooth sensitivity occurred in 36% and 8% of the OPA and PLA groups, respectively. No relation between gingival bleeding and treatment group (p = 1.000) was found.

Conclusions: Nightguard vital bleaching with 10% carbamide peroxide, done according to the clinical protocol used in this study, was effective for lightening teeth, both for the period immediately after treatment and for the 6-month follow-up period. Of the 2 main side effects assessed, tooth sensitivity was more prevalent than gingival irritation; however, both were transient and disappeared at the end of treatment.