ABSTRACT
The risk of the enamel damage increases if the debonding fracture site shifts toward the junction between the enamel and adhesive. The aim of this study was to determine the in-vitro bond strength and the fracture site after debonding the mechanically-bonded ceramic and metallic brackets. Sixty extracted premolars were randomly selected from orthodontic patients in a private clinic. All the samples were divided into two groups and 30 metallic and 30 ceramic brackets were mechanically bonded to the teeth, using light curing adhesive. After one week, all the brackets were debonded by bracket-removing pliers assembled on a testing machine. This design simulated clinically-applied debonding compressive forces precisely. By the use of stereomicroscope and trans-illumination technique, the amount of adhesive remnant on the brackets' surfaces or on the teeth was evaluated and calculated using Photoshop and Auto Cat software program in the bonded areas in order to determine different fracture sites. Descriptive analysis was used to describe the findings and independent t-test was used to compare the differences between the two bracket groups. Debonding fracture was mostly observed in the interface between brackets and adhesive and within adhesive but there were no statistically significant differences in the location of the debonding fracture between the two groups. The risk of enamel damage after debonding both metallic and ceramic brackets is low due to the minimal chance of debonding failure between the enamel and adhesive