The aim of our study was to compare shear bond strengths of orthodontic brackets bonded with chemically cured, halogen light cured and LED cured adhesive systems. 45 extracted human premolar teeth were randomly divided into 3 groups. Bicuspid metal brackets were bonded on first group of teeth with chemically cured bonding system (Rely-a-Bond). Second group were bonded with halogen light cured bonding system (Light Bond). Last group were bonded with LED light cured bonding system (Light Bond). Each specimen was then loaded to universal testing machine. Bond strength was determined in the shear mode at a crosshead speed of 0.5 mm/min. Descriptive statistics, including the mean, standard deviation, standard error, minimum and maximum values were calculated for each of the groups tested. One-way analysis of variance (ANOVA) and Tukey multiple comparison tests were used to compare shear bond strengths of the groups. Highest values of the shear bond strengths were determined in LED group (Group 3), while Halogen group (Group 2) produced the lowest values. According to the results of analysis of variance (ANOVA), the difference between groups is significant (p<.05). Results of Tukey multiple comparison test indicated that this difference was significant between LED (Group 3) and halogen (Group 2) groups. No significant difference was found between LED (Group 3) and chemical (Group 1) group. In conclusion, shear bond strengths produced by each method were sufficient to withstand orthodontic forces. Highest values of shear bond strengths were determined with LED polymerization, while lowest values were obtained from the specimens polymerized with Halogen light.

Keywords: LED, Halogen, Connecting strength