Effect of Adjunctive Universal Whitening Enhancer on Enamel and Dentin

Objectives: The purpose of the study was to evaluate the effects of a novel adjunctive universal tooth whitening enhancer liquid (UTWE; 2.0% hydrogen peroxide with surfactants and solvents) on enamel and dentin microhardness. Additionally, levels of peroxide found in tooth pulp chambers were assayed. Methods: Twenty freshly extracted human maxillary incisors were randomly assigned to either the experimental or placebo group (10 each). Both groups received treatment to simulate the conditions of a chairside bleaching procedure with bleaching light, using three (3) ten-minute cycles of either UTWE or Placebo (water only) pre-treatment followed by gel application. The bleaching gel used was a commercially available 20% hydrogen peroxide chairside whitener with matched bleaching light. After treatment, all teeth were then cross-sectioned, and subsurface enamel and dentin were polished. Knoop Hardness Number (KHN) was determined using a Vickers indenter microhardness tester (HMV2000, Shimadzu, Japan) at 200 g load for 10s (dentin)/15s(enamel). The peroxide concentration found in pulp chambers were also determined spectrophotometrically. Data were analyzed using using the Student t-Test. Results: There were no significant differences in subsurface enamel and dentin KHN values between the UTWE and Placebo treated teeth (P > 0.412). Furthermore, the mean concentration of peroxide found in the pulp chambers was 0.064 +/- 0.09 mM for UTWE and 0.031 +/- 0.07 mM for Placebo; the difference was statistically significant (P < 0.05). Conclusions: Under conditions of the study, pre-treatment with the experimental adjunctive universal whitening enhancer fluid did not adversely affect the microhardness of human enamel or dentin. Peroxide penetration through the tooth structure was more than twice as high in UTWE pre-treated teeth, thus demonstrating it may have the capability of enhancing bleaching treatment for deeper seated intrinsic stain, yet the levels found were still over 2,000 times below the concentration reported to cause pulpal enzyme damage.