Reliability of Digital and Plaster PAR Index Scores

Objectives: The objective of this research is to examine the reliability 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 reliability 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 models were compared using intraclass correlation coefficients (ICC). Intra-rater reliability was good for plaster (ICC =0.919) and for digital models (ICC= 0.905). Inter-rater reliability was also good for plaster (ICC=0.912) and digital models (ICC=0.883) Conclusion: The PAR index was shown to be reliable when measuring malocclusions using digital study models compared to plaster models.