Enamel colour changes after debonding using various bonding systems

Objective: To test the possible association between enamel colour alteration and resin tag depth. Design: In vitro laboratory study. Setting: Department of Orthodontics, Alexandria University, Egypt. Materials and methods: Fifty freshly extracted human premolar teeth were equally divided randomly into a control and four experimental groups. Teeth in Group I received only enamel prophylaxis. Teeth in Groups II and III were etched with 35% phosphoric acid for 15 and 60 seconds, respectively. Teeth in Group IV were conditioned with Prompt L-pop self-etching primer and in Group V with Xeno III self-etching primer, according to the manufacturer's instructions. Orthodontic brackets were bonded to the teeth in all experimental groups using Transbond XT composite. Following bracket debonding, finishing and polishing were performed. Enamel colour was evaluated spectrophotometrically at baseline and then after debonding, with the corresponding colour differences Delta E calculated. Resin tags lengths were measured on sectioned teeth in each experimental group under scanning electron microscope. Results: All experimental groups showed clinically perceivable colour change after debonding and finishing as all values were exceeded the clinical colour detection threshold of Delta E=3.7 units. Significant differences (P < 0.05) in resin tag length were found in all experimental groups. Significant moderate correlation was found between colour change and resin tags length when all teeth were combined and tested, irrespective of group. Conclusions: Moderate evidence exists that shorter resin tag penetration produces less change in enamel colour following clean-up and polishing. Self-etch primers produce less resin penetration and these systems may produce less iatrogenic colour change in enamel following orthodontic treatment.