The effect of tooth bleaching on substance P expression in human dental pulp

The purpose of this study was to quantify the effect of tooth bleaching on substance P (SP) expression in healthy human dental pulp. Forty pulp samples were obtained from healthy premolars in which extraction was indicated for orthodontic reasons. Thirty of these premolars were assigned into three different tooth-bleaching protocols: group 1 (n = 10): Opalescence Xtra Boost (Ultradent Products, South Jordan, UT) (38% H(2)O(2)) for 15 minutes; group 2 (n = 10): Lase Peroxide (DMC, Brazil) (35% H(2)O(2)) activated with infrared laser diode (Biolux; BioArt, Brazil) for 3 minutes, and group 3 (n = 10): Zoom! Whitening System (Discuss Dental, Culver City, CA) (25% H(2)O(2)) light activated for 20 minutes. The remaining 10 healthy premolars serve as a control group. Teeth were anesthetized immediately after bleaching and were extracted 10 minutes later. All pulp samples were processed and SP was measured by radioimmunoassay. Greater SP expression was found in the Zoom! Whitening System, followed by the Lase Peroxide group, Opalescence Xtra Boost, and the lower SP values were for the control group. Analysis of variance showed statistically significant differences between groups (p = 0.0001). Tukey HSD post hoc tests showed significant differences in the light (p < 0.01) and laser (p < 0.05) activated bleaching systems when compared with control values. It can be concluded that light- and laser-activated tooth-bleaching systems increase SP expression in human dental pulp significantly higher than normal values.