One Year Clinical Follow-up of the rebound of bleached teeth Color using of two different in-office bleaching techniques.

Aim: A clinical study to assess the rebound of the color of bleached teeth for one year follow up. Materials and methods: Thirty non-smoker patients (18-23years) having anterior upper and lower segments from canine to canine with an average shade of A4 were selected. Teeth were checked to be free of caries, restorations, hypoplastic lesions, stains, and cracks. The shades were measured mainly by using Vita classic visual standardized shade guide and confirmed by spectrophotometer (easy shade) only in case of any confliction in the scores of both evaluators. Cooperative patients ready for follow up were involved in the present study. Segments were equally and unsystematically distributed into 2 groups (30 segments each) according to the bleaching system used, Group I: Chemical activated bleaching system 40% HP (White Smile power whitening YF) & Group II: light activated bleaching system, mixed 32% HP (White smile light whitening AC). Each group involved 15 upper and 15 lower segments at the 30 pts. Every group was distributed into 2 subgroups according to the location whether upper or lower segments. The manufacturer’s instructions were followed and applied in every bleaching process. Every tooth shade was documented before bleaching, 24 hours after