Comparison of three indices in evaluation of orthodontic treatment outcome.

Three indices measuring outcome of orthodontic treatment were evaluated and compared in 39 specialist-treated individuals (group 1) and in 20 specialist-treated individuals who had undergone orthognathic surgery (group 2). The outcome was evaluated in accordance with the modified Indication Index, the modified ISMHB (Index of the Swedish Medical Health Board), and the PAR (Peer Assessment Rating) Index. Pre- and post-treatment need scores on the basis of the three indices were estimated. The ranking order of the individuals by the different indices was compared in the two groups separately, before and after treatment. Associations between the Indication Index and the ISMHB were consistently stronger than associations between the PAR Index and the two other indices, for which the variations were great. The reasons for the great variations seemed to be the different bases for assessment used and the different constructions of the indices: the PAR Index estimates deviations from an ideal occlusion, and the other indices evaluate treatment need. The outcome describe by the indices differed with regard to the pre- and post-treatment scores and the ranking order of the individuals. Of the three indices, the Indication Index was found to be the one most suitable for estimating treatment outcome in terms of decrease of treatment need, and the PAR Index was unsuitable for estimating treatment need.