Effect of maintenance media on shear bond strength of orthodontic brackets

In orthodontics، bonding is a term commonly used to describe the connection of brackets to tooth surfaces using bonding resins. Different factors are involved in bond strength of orthodontic brackets، among those is the maintenance medium. To investigate the effect of maintenance medium on shear bond strength of orthodontic brackets. This was an experimental study performed on 105 healthy premolars in 2012. The teeth were kept at ambient temperature for three months in storage media such as distilled water، formalin 10%، chloramine T 0. 5%، thymol 0. 2%، ethanol 70%، isotonic saline solution، and sodium hypochlorite 5. 25%. Buccal surface of teeth were prepared with 37% phosphoric acid etched for 30 seconds and then washed with water for 15 seconds. Later، stainless steel brackets (Dentarum with 0. 018 inch slots) were installed with composite and Transbond XT (3M USA) in the geometric center of the buccal surface which was perpendicular to the long axis of teeth. The shear bond strength of brackets was measured by universal testing machine at a speed of 1mm/min. Data were analyzed by one way variance، Npar، ANOVA and Tukey’s test. The highest mean shear bond strength (20. 95 MPa) was found in chloramine T 0. 5% and the lowest in formaldehyde 10% (13. 08 MPa)، showing a significant difference between two media. ANOVA revealed a significant difference between the mean shear bond strength within the groups whereas Tukey’s test failed to demonstrate any significant difference in alcohol and thymol with another groups. The teeth kept in chloramine T 0. 5% showed significant differences in shear bond strength compared with samples stored in formalin 10% and isotonic saline solution. Samples kept in distilled water revealed significant differences with those maintained in formalin 10%. Based on the results of this study، a reasonable strength was only found in chloramine-T 0. 5% compared to control samples (distilled water).