Spectrophotometric Evaluation of Hydrogen Peroxide Penetration into the Pulp Cavity

Objectives: To investigate hydrogen peroxide (HP) penetration level into the pulp cavity based on type of whitening systems used.
Methods: Sixty extracted human molars were prepared and randomly assigned into four groups (n=15/per group), including Group NC: Glycerol gel; Group QPRO: 20% HP varnish (Zoom Quick Pro, Philips Oral Healthcare, LA, CA, USA); Group ZOOM_NL: 25% HP gel (Zoom Chairside Whitening Gel, Philips Oral Healthcare); and Group ZOOM_WL: 25% HP gel (Zoom Chairside Whitening Gel, Philips Oral Healthcare) with LED light activation (Zoom WhiteSpeed, Philips Oral Healthcare). Teeth were kept at room temperature in a closed humid chamber with 100% relative humidity throughout the 30-minute treatment procedure. HP penetration levels were measured after the 30-minute whitening treatment and estimated with leucocrystal violet and horseradish peroxidase. A standard calibration curve with known amounts of HP was used to determine the amount in microgram equivalents in the samples. Descriptive statistics were conducted, and one-way ANOVA followed by the post-hoc Tukey’s HSD test was performed to assess the difference in the HP penetration levels among the four experimental groups (alpha=0.05).
Results: Results of the one-way ANOVA showed that there was a significant effect of the type of whitening systems for HP penetration level (F(3,56)=33.15; p<0.0001), indicating a significant difference in mean HP penetration level among the four experimental groups. The post-hoc Tukey’s HSD test revealed that mean HP penetration level obtained from ZOOM_WL (1.568±0.753ug/ml) was significantly greater than those obtained from the other three experimental groups, while the mean HP penetration level observed in NC group
(-0.131±0.003ug/ml) was significantly lower than those observed in the other three experimental groups. No significant difference was found between QPRO (0.558±0.485ug/ml) and ZOOM_NL (0.615±0.0.282ug/ml).
Conclusions: HP penetration levels vary based on whitening systems used. The use of light activation enhances penetration levels.