Factors Affecting Orthodontic Bracket Failure Rate

Objectives: To study the failure rate of orthodontic brackets, and to examine the effect of different variables on bracket failure.
Methods: The study was executed as a retrospective cohort study. Files of 208 patients, treated with fixed appliances in 2015 in the city of Turku, Finland, were reviewed. Bracket failures were recorded along with the age and sex of the patient, the number of brackets that were bonded, the jaw and tooth type, the dates of beginning and end of the treatment, the orthodontist who performed the bonding, the cement that was used, and the date of failure. The survival rate was determined with the Kaplan-Meier analysis and log rank test, and the comparison of the survival distributions with respect to the different variables were carried out with the Cox proportional hazards model with shared frailty.
Results: Altogether the patients had 3744 brackets, 8.0% of the brackets failed during the treatment. Brackets in mandible failed more often (9.7%) than those in maxilla (6.4%)(p<0.05). Mandibular incisors showed highest failure rate (13.6%), followed by maxillary molars (12.2%). Maxillary canines exhibited least failures (5.0%). The sex and age of the patient did not have an effect on the failure rate. The failure risk was higher when a bonding system with a self-etching primer was used. The bonding technique of the operator also had an effect, with one of the orthodontists having a higher risk for failure (13.3% vs 4.1% and 7.9%) (p<0.05). For the failed brackets, the mean duration before a failure was 188 days (6.2 months), while the mean duration of the entire treatment was 481 days (15.8 months).
Conclusions: The variables that increased the likelihood of bracket failure were the location of the tooth in the anterior mandible, the choice of bonding system and the technique of the operator.