Surface changes and acid dissolution of enamel after carbamide peroxide bleach treatment

Objectives: To evaluate the effects of home bleaching (carbamide peroxide) on enamel surface morphology and the degree of acid dissolution. Methods: Buccal surfaces of 15 caries-free human premolars were used in the study. The 15 teeth were cut in half in a buccal-lingual direction at midline; in total, 15 pairs of specimens were obtained. Group A consisted of five pairs that studied surface morphology change and Group B consisted of 10 pairs that studied the susceptibility of bleached enamel to acid dissolution. Tooth halves were prepared following a fluoride-free prophylaxis paste cleaning. One half of the tooth was untreated (control), and the other half was bleached (experimental) for eight hours daily for 10 days using 10% carbamide peroxide. Tooth samples were then stored in distilled water for seven days, after which scanning electron microscopy (SEM) was performed on Group A. Only halves from the same tooth were compared to rule out natural variations between teeth. Group B was etched with 37% phosphoric acid before being examined by SEM. The severity of the acid attack was graded from I to V, and the grades of each pair were compared. Results: Results of the SEM observation showed that surface porosity slightly increased after bleaching, and more surface dissolution by phosphoric acid was seen with bleached, compared to unbleached, enamel.