Factors affecting the outcome of orthodontic treatment within the general dental service.

Previous studies have suggested large differences in the outcome of orthodontic treatment as measured by the PAR index in two adjacent regions of England. The aim of this prospective study was to identify any factors contributing to the mean PAR score reduction in the North Western region and the Mersey region. Forty-one practitioners submitted 375 sets of start models and 250 end of treatment models. The study ran for 36 months. There were no significant differences detected in the type of malocclusion treated or in outcome of treatment between the two regions with respect to the PAR and IOTN indices. This study did, however, clearly demonstrate that qualified orthodontic practitioners were achieving significantly better results with fixed appliances that practitioners with no orthodontic qualification who used fixed appliances.