Does mechanical locking-base ceramic brackets reduce cracks at debonding?

Objectives: Debonding of chemically bonded ceramic brackets has been mostly led to enamel damages. This study aimed to evaluate enamel cracks followed by debonding ceramic brackets with mechanical retention. Study Design: Sixty extracted human premolar teeth were randomly divided into two groups. Metallic brackets and recently available ceramic brackets with mechanical retention were bonded to the teeth in first (MB) and second (CB) group respectively. After a week, the brackets were debonded using a pair of bracket-removing pliers assembled to a testing machine. Optical stereomicroscope and trans-illumination techniques were used to calculate the cracks and measure their length before bonding and after debonding. Paired t-test, independent t-test and McNemar's test were used for statistical analysis. Results: Metallic brackets showed higher mechanical bond strength compared to ceramic brackets with mechanical locks. In both groups, higher numbers of teeth with enamel cracks and a significant increase in the length of enamel cracks were evident subsequent to debonding. Inter-group deference in the number of teeth with cracks and the length of enamel cracks before or after debonding was not significant. Conclusions:The risk of producing enamel cracks after debonding of ceramic brackets with mechanical retention is the same as metallic brackets