To study the effects of the preventive application of a desensitizing agent before tooth bleaching on tooth sensitivity.

Twenty patients, who received in-office bleaching in Affiliated Stomatological Hospital of Foshan University from May 2015 to Oct 2016, were recruited according to the inclusion criteria. The patients were numbered in sequence and randomly divided into two groups. For group one, their left anterior teeth were set as the experimental group and the right side as the control. In contrast, in group two, the left anterior teeth were taken as the control group and the right side as the experimental group. Desensitizing agent (Green Or) for the experimental group and placebo (distilled water) for the control group were applied on tooth surface before the bleaching treatment. The incidence and intensity of tooth sensitivity immediate after operation and within 1 week were recorded using VAS scale. The Chi-square test and Mann-Whitney rank-sum test were applied for statistical analysis.

The incidence of tooth sensitivity immediate after operation was 28.33% and 62.50% in the experimental and control group, respectively. Meanwhile, the sensitivity in 1 week after tooth bleaching was 11.67% and 43.33% in the experimental and control group, respectively. The incidence of tooth sensitivity immediate after operation and within 1 week was significantly higher in the control group than that in the experimental group (χ²_imm=29.606, χ^2post=30.178, P<0.001) . The intensity of tooth sensitivity immediate after operation and within 1 week was significantly higher in the control group than that in the experimental group (Z_imm=-5.999, Z_post=-5.659, P<0.001) .

The preventive application of the desensitizing agent before tooth bleaching can effectively reduce the incidence of tooth sensitivity and relief the symptom.