Methods: Retrospective chart reviews were performed on 436 patients presenting for orthodontic treatment between 1981 and 2005 to a combined pediatric and orthodontic private practice. The subjects demographics (age, gender) and clinical characteristics (appliance and cement type, molar classification, open bite, crossbite location, caries history, oral hygiene and compliance) were assessed using logistic regression (SAS 9.1) as possible risk variables of MEA failure defined as cement loss, solder breakage, split bands, soft tissue impingement, eruption problem, or bent wire.
Results: A total of 19% (N=84) of the appliances failed during the study period with the median wear time for all MEA of 216 days (IQR=126 days). The mean age at the time of appliance insertion was 8 years 4 months (SD= 1.72) with the most common type of failure being cement loss (69%). Children with a malocclusion other than Class I were more likely to have treatment failure (adj OR, 1.91; 95% CI, 1.16-3.14). Conditional on the type of malocclusion, the estimated odds ratio for the probability of the Quad helix treatment failing relative to Hass was 3.60 (95% CI, 1.92-6.75). No statistically significant difference in the odds of failure between the Hass-crib and Hass or between Hyrax and Hass appliances was observed.
Conclusions: Quad helix when compared to other MEA appliances and the presence of a malocclusion other than Class I were statistically significant predictors of an increased likelihood of treatment failure. This information can help guide clinical decision making when addressing crossbite corrections in the primary and mixed dentition.