Effects of Over-the-counter Bleaching Agents on Properties of Dental Enamel

Objectives: Vital dental bleaching has lately presented an exponential increase due to is conservative approach to treat discolored teeth. However, multiple bleaching products can be directly purchased by the patient (over-the-counter or e-commerce) without professional supervision.Thus, this study aims to evaluatethe effects of four OTC bleaching productson properties of dental enamel.
Methods: Twenty human pre-molar crowns (REB H17-02331) were randomly assigned into 4 groups (N=5): G1:Poladay 9.5%HP (SDI); G2:White Teeth Global 44%CP (BleachPro Whitening); G3:Crest 3D White (Procter&Gable) unknown HP%; G4:TeethWhiteningGel (HiSmile) undisclosed HP%. Each crown was sectioned in 4 quarters, segments were imbedded together into an epoxy resin block, flattened and polished. Each quarter was treated with four different bleaching time as follows: control/no-bleaching, 2-week, 4-week, or 8-week. Bleaching materials were applied to enamel surfaces as per manufacturer’s recommendations.Enamel surfaces were analyzed in ultra-micro hardness, elastic modulus, superficial roughness, and SEM. Each material was analyzed on hydrogen peroxide content by tritation.
Results: Enamel surfaces treated with OTC bleaching agents presented ultra-micro hardness values significantly lower than the control (p<0.05) for all materials and treatment times, except G4 (HiSmile). Modulus of elasticity was significantly reduced after bleaching with G1 (Poladay) for 2- and 4-week time, and with G4 (HiSmile) at 2-week (p<0.05). Surface roughness was significantly increased by bleaching time on G3 (Crest3DWhite) at 2-week (p<0.05). Hydrogen peroxide present on the materials tested were G1:11.46%, G2:14.1%, G3:3.31%, and G4:0.03%. Among materials, significantly lower ultra-micro hardness and higher surface roughness were observed for bleaching products with higher HP% (p<0.05), G1 (Poladay) and G2 (White Teeth Global).
Conclusions: Over-the-counter bleaching products containing hydrogen peroxide can significantly alter human dental enamel ultra-microhardness, modulus of elasticity and surface roughness. The application time also affects those properties; however, it varies for each bleaching product.