Validity of Digital and Plaster PAR Index Scores

Objectives: The objective of this research is to examine the validity of the Peer Assessment Rating (PAR) index in measuring malocclusion with computerized digital models. Computer based digital orthodontic models have been shown to be valid and reliable when making measurements of tooth size and simple diagnosis of dental malocclusion. The PAR index is used to determine the degree of malocclusion, results of treatment, and degree of improvement and has been shown to be valid and reliable. Clinicians and institutions often utilize the PAR index to audit treatment results achieved in their clinics. Researchers have also regularly used the index in examining clinical results. The validity of PAR scores from digital models and plaster models that have been previously scored and standardized for the PAR index has not been established. Methods: Ten examiners were trained to score digital and plaster models using the PAR index. Thirty standardized and previously scored plaster PAR models were digitized using digital study model technology (Orthocad). The standardized plaster and digital models were randomized and scored by the ten examiners. All measurements were repeated by all examiners at a second session. Results: Plaster and digital scores were compared to the standardized PAR scores for validity. The Intraclass Correlation Coefficients (ICC) for plaster models ranged from .808-.926. The overall ICC for plaster models was .891 with a 95% confidence interval (CI) of .829-.940. The ICC's for digital models ranged from .846-.922. The overall ICC for digital models was .878 with CI of .811-.931. Conclusion: The PAR index was shown to be valid when measuring malocclusions using digital study models compared to plaster models.