The effect of light activated bleaching versus orange juice on enamel s micro-hardness

Objective: To evaluate the surface micro hardness of enamel bleached with 38% H_2O_2 (Light activated) versus tetra pack orange juice. Method: A total sample of (n=23) sound crowns of human third molars, which were extracted because of periodontal reason were included in the study. Longitudinal sections were made at buccolingual direction using diamond disks (0.2 mm) under water lubrication to obtain enamel slabs measuring (3 mm x 3 mm) then slabs were embedded in polystyrene resin by using 2.0-cm diameter PVC molds, leaving the external enamel surfaces uncovered by the resin. After 24 h, enamel slabs were removed from the molds. These 45 enamel slabs were further subdivided in to 3 groups (A, B, C). Each group contains fifteen specimens. Group Awas placed in artificial saliva at 37 °C within the incubator (Memart, Germany). Whereas, Group B was treated with Power whitening gel (whitesmile 2011, Germany) activated with light and Group C was immersed in orange juice. Micro-hardness measurements were performed on specimens pre and post treatment with orange juice immersion and bleaching. Data analyses were performed by using Statistical Package of Social Sciences (SPSS) v. 20.0. Assessments of changes in micro hardness on different time interval as well as due to different materials were analyzed by RMANOVA with post hoc. Results: Surface micro hardness decreased from 152.8 (S.D. 1.86) to 152.1 (S.D. 2.03) in Group A (p = 0.546). A much smaller reduction in the surface micro hardness was also noticed in Group B from 152.8 (S.D. 1.86) to 152.1 (S.D. 2.03) (p = 0.384). Statistically significant reduction in surface micro hardness was observed in the Group C (p 0.0001) but not in the hydrogen peroxide and the control groups (p 0.05). Conclusions: Enamel surface becomes considerably softer and rougher after orange juice challenge as compare to 38% hydrogen peroxide bleaching.