Comparison of the Direction of Enamel Microcracks in Five Different Debonding Methods: An in Vitro Study

Background: Debonding of orthodontic metal bracket is a routine part of fixed orthodontic treatment. The purpose of this in vitro study was to evaluate the direction of enamel cracks before and after debonding the metal orthodontic brackets in five different techniques. Methods: Two hundred extracted human premolars were randomly divided into five groups in this in vitro study. Metal brackets were bonded with Transbond XT (3 M Unitek, Monrovia, CA, USA) light-cured adhesive. Then the brackets were removed with one of these methods: ultrasonic scaler, ligature cutter plier, bracket removal plier, how plier, crown remover. Direction of the enamel cracks were examined by stereomicroscope and compared. Statistical analysis was done with Paired t-test and Chi-squared test. P < 0.05 was considered as significant. Results: After debonding, mixed type had the highest frequency (80.9 %) and no specimens were observed with horizontal crack. There was no significant change in the pattern of directions in before-after comparison (p=0.007. Mixed pattern was less common in ultrasonic group compared to crown remover and ligature cutter groups (p=0.007 and 0.035 respectively). Conclusion: All of the five debonding methods in the current study had no significant change on the microcrack patterns and there were no horizontal cracks after debonding. Ultrasonic device had the least number of mixed cracks after debonding.