Influence of bleaching and desensitizer application on bracket bond strength

Objective: The aim of this study was to compare the shear bond strengths (SBS) of orthodontic brackets bonded to human enamel with a self-etching primer (SEP) after bleaching, desensitizer application and combined treatment. Materials and Methods: Forty-eight defect-free premolars were randomly assigned into four groups (n=12). Group1: 15% hydrogen peroxide office bleaching agent (Illumine Office, Densply), Group 2: 15% hydrogen peroxide office bleaching agent + Bis- Block desensitizer (Bisco), Group 3: Bis- Block desensitizer, Group 4: No treatment (control). Metal brackets were bonded with SEP (Transbond Plus, 3M) and light-cure adhesives paste (Transbond XT,3M). The specimens were stored in deionized water at 37 degrees C for 24 hours and then tested in shear with a universal testing machine at a crosshead speed of 5 mm/min until the brackets debonded. The mode of failure of the brackets was determined by a modified adhesive remnant index. The shear bond strength data were subjected to Kruskal-Wallis test. Results: The results showed that bleaching, bleaching plus desensitizer, and desensitizer procedures significantly reduced SBS of the orthodontic brackets (P < 0.05). No statistically significant difference was found between bleaching, bleaching plus desensitizer, and desensitizer groups (P > 0.05). The predominant mode of failure for the three groups (Group1,2,3) was at the enamel-adhesive interface leaving 100 % of the adhesive on the bracket base. Conclusions: Because bleaching and desensitizer treatment significantly influenced shear bond strengths of orthodontic brackets on human enamel, they should be postponed until the completion of orthodontic treatment.