Effect of Application of Two Different Bleaching Agents on Human Enamel In vitro

Objective This study was done to investigate the effects of application of two different bleaching techniques and agents on enamel hardness and surface morphology. Material and methods twenty six intact human first premolars extracted for orthodontic reasons were used in this split-tooth in vitro study. The specimens were randomly divided into two equal groups and sectioned buccolingually. Half of each crown was treated and the other half served as its control. For Group 1 (G1), an in-office bleaching technique was used. The specimens were treated with UV light activated H2O2 25 % (zoom whitening system) according to manufacturers instructions. For Group 2 (G2), an at-home bleaching protocol was used with 20 % carbamide peroxide 4 hours daily for 14 days. The effects of bleaching agents on enamel were evaluated using surface roughness analysis, microhardness test (MHT) and scanning electron microscopy (SEM). Results This study revealed that bleaching resulted in significant decrease in microhardness of enamel surface. SEM investigation demonstrated that the bleaching agents affected enamel surface morphology producing erosion of outer enamel layer. These findings were pronounced in in-office bleaching more than in at-home bleaching. conclusion The high concentration of bleaching agents could affect intensively enamel hardness and alter surface morphology.