The PAR Index (Peer Assessment Rating): methods to determine outcome of orthodontic treatment in terms of improvement and standards.

In orthodontics it is important to objectively assess whether a worthwhile improvement has been achieved in terms of overall alignment and occlusion for an individual patient or the greater proportion of a practitioner's caseload. An objective measure is described that has been validated against the subjective opinions of 74 dentists. Using the weighted PAR Index it was revealed that at least a 30 per cent reduction in PAR score is required for a case to be considered as 'improved' and a change of 22 PAR points to bring about 'great improvement'. For a practitioner to demonstrate high standards the proportion of an individual's case load falling in the 'worse or no different' category should be negligible and the mean reduction should be as high as possible (e.g. greater than 70 per cent). If the mean percentage reduction in PAR score is high and the proportion of cases that have been 'greatly improved' is also high, this indicates that the practitioner is treating a great proportion of cases with a clear need for treatment to a high standard.