In-Vitro Effects of OTC Bleaching on Enamel and Dentin Bonding

Objectives: This study is designed to determine the effect of a 10% hydrogen peroxide bleaching on enamel and dentin bonding. Methods: Twenty bovine incisors were treated with one week's worth of normal bleaching. One half of the incisors were bleached with Crest Whitestrips Premium (B) the other half received no bleaching treatment (C). Bleaching strips were applied for 30 minutes, removed and teeth placed in water for one hour. A new bleach strip was applied and the process repeated fourteen times to simulate one week of bleaching. The incisors were immediately sectioned into four pieces: enamel control (EC), enamel bleached (EB), dentin control (DC) and dentin bleached (DB). Twenty of each specimen were prepared and all specimens were bonded as soon as possible. Specimens were removed from the storage water, dried, etched with 35% phosphoric acid for 10 seconds, washed and bonding agent (Peak LC) applied and polymerized. A 2.38 mm diameter column of Filtek Supreme A2 was bonded to the surface and polymerized as per manufacturer's instructions. Specimens were stored in water for at least 48 hours to assure complete polymerization. Specimens were subjected to a shear force on an Instron at a crosshead speed of 1.0 mm/min. The force at failure was recorded. Mean shear strength (+se) was calculated and significant differences were calculated with a two-tailed Student's T-test. Results: Mean shear force (MPa +s.e.) were EC- 43.1(+ 1.9), EB- 38.4(+ 1.9) with p< 0.054 and DC- 20.8(+ 2.4), DB- 21.7(+ 2.4) with p< 0.79. Conclusions: Though no significant differences were found for dentin, the enamel bonding revealed near significant differences. This agrees with data from prior published studies for dentist prescribed bleaching agents. Dentists should inquire as to whether patients have been using OTC bleaching agents prior to bonding to achieve the best results.