Use of the PAR index in assessing the effectiveness of removable orthodontic appliances.

The dental study casts of 150 consecutively completed removable appliance cases were examined before and after orthodontic treatment using the PAR index. Eighty-nine per cent were classified either as 'improved' or 'greatly improved'. Of the 16 cases classified as 'worse, no different', six were mixed dentition cases with limited treatment objectives (which were successfully achieved) and three were permanent dentition cases where only one tooth was being aligned. Using predefined criteria removable appliances were shown to be most effective in treating cross-bites, ectopic tooth position, anterior spacing, and overjet, and less effective in treating crowding, rotations, and molar relationships.