Survival and failure rate of lower lingual bonded retainers: A retrospective cohort evaluation

The objectives of the study were to evaluate the survival rates for lower lingual retainers (LLRs) and to establish a correlation between patients' treatment-related factors (age, sex, malocclusion, appliance used for treatment, teeth bonded, retention protocols) to the survival of LLRs.

A total of 765 subjects [474 females and 291 males: mean age = 24.29 ± 10.67 years] between 2013 and 2022 were included. A customized data collection form was utilized to gather the data from the electronic health record (EHR) of subjects. Patient-related factors, crowding or spacing, deep bite or open bite and duration of treatment were extracted from patients' files. Kaplan-Meier estimator was used for the survival function, whereas Cox proportional hazards regression models were used to associate risk factors with retainer survival.

328 (42.9%) subjects had their LLRs failed, and the survival period was on average 17.37 ± 22.85 months. On the other hand, the follow-up period for the retainers that did not fail was on average 47.19 ± 23.66 months. 192 (28.3%) subjects had segment failure (retainer detached from 3 teeth or less), while 51 (7.5%) subjects had failures in more than 3 teeth (complete). None of the evaluated clinical variables were significantly associated with LLRs failure except for the bite category (P = .013) and the appliance used for treatment (P < .001).

Success rate for LLRs was 57.1% over 47.19 months, failure rate was 42.9% over 17.37 months. The presence of deep bite and treatment with aligners were significantly associated with increased failure rate.