Orthodontic correction of overjet/overbite ('parrot mouth') in 73 foals (1999-2013)

There are limited reports on the efficacy of functional orthodontic correction of overjet or overbite in foals.

To report the outcome of using orthodontic tension bands in combination with an inclined plane biteplate in the treatment of overjet, with or without concurrent overbite, rates of correction of these 2 malocclusions and associated complications. And to examine factors associated with outcomes.

Retrospective case series.

Clinical records for 73 foals treated at a single clinic, by the same surgeon were analysed. Overall change and rates of change in overjet and overbite were calculated. Associations between potential explanatory variables including age, severity of initial malocclusion and surgeon experience were examined using linear regression.

Records for 73 foals (43 colts, 30 fillies) were evaluated. The median number of implant placements per animal was 2 (range 1-4). Of 61 cases with complete records, reduction in overjet and overbite dimensions were achieved in 95% and 90% of foals, respectively, with mean reductions in malocclusions of 9.9 and 8.4 mm, respectively. Complete reduction in overjet was achieved in 25% (15/61) and reduction of malocclusion dimensions to ≤5 mm (i.e. functionally corrected) was achieved in 51% (31/61). Increasing animal age was significantly associated with decreased total reduction in overjet and decreased rate of reduction in overbite. Increased original severity of overbite was significantly associated with increased rate of its correction. Short-term complications included intraoperative haemorrhage, transient facial nerve neuropraxia and irritation of the mare's udder by the brace. Longer-term complications included cheek teeth diastema formation and incisor discoloration and maleruption.

Using this technique, correction or improvement of these malocclusions is rapid, with minimal complications. Often more than one implant is required. Animal age at the start of treatment is associated with rate and amount of correction achievable, so initiating treatment at an early age is recommended.