Factors influencing the outcome and duration of removable appliance treatment.

The study models and records of 150 consecutively completed removable appliance cases were analysed and the influence of various factors assessed on both the change in Peer Assessment Rating (PAR) score produced by treatment and the duration of treatment. For the purpose of analysis the material was divided into two groups; a functional appliance/headgear group (n = 43) and an upper removable appliance group (n = 103). The initial PAR score accounted for 71 per cent of the variation in PAR change in the functional/headgear group when combined with the sex of the patient; females on average showing a further improvement of 3 PAR points over equivalent males. The initial PAR score alone accounted for 68 per cent of the variation in PAR change in the upper removable appliance group. Sixty per cent of the variability in treatment duration could be explained in the functional/headgear group by the initial PAR score and a binary variable indicating whether three or more appliances had been required. Fifty-six per cent of the variability in duration in the upper removable appliance group was explained by the number of appliances used alone. Regression equations for prediction of outcome and duration of removable appliance treatment are given.