Practical application of the PAR index: an illustrative comparison of the outcome of treatment using two fixed appliance techniques.

A retrospective assessment of treatment outcome in a group of 82 orthodontic fixed appliance cases was carried out using the Peer Assessment Rating Index (PAR) in order to explore the usefulness of the PAR index as a means of differentiating the change associated with treatment. Two different fixed appliance techniques, the pre-adjusted Edgewise and the Begg appliance had been used to treat these cases, and all had been under the care of one Consultant Orthodontist. The mean percentage reduction in PAR for the group as a whole was 74 per cent. Comparison of the two different appliance types found that the pre-adjusted Edgewise group achieved a significantly greater reduction in PAR score (81 per cent), than the Begg group (65 per cent). Cases with a low PAR score prior to treatment tended to fare more poorly in terms of percentage reduction and this was more marked for those cases treated with the Begg appliance. Although the PAR index has a high degree of reproducibility, it was found that even the small error present can lead to problems of interpretation if the nomogram categories are used as a method of comparison. Some potential problems in undertaking studies such as this using the PAR index to assess treatment outcome are discussed.