Assessment of Orthodontic Treatment Outcomes Using the PAR Index

Objectives: The PAR Index (Peer Assessment Review) is a system designed to give a single score of the severity of malocclusion. There are numerous studies supporting its validity and reliability. In this study we utilized the PAR index to evaluate casts of orthodontic patients, before and after treatment. The goal was to examine possible relationships between the decrease in severity of malocclusion and other variables, particularly the pretreatment severity, to determine if more severe cases derive significantly greater benefit from orthodontic treatment than less severe ones. Other variables evaluated included treatment time and gender.

Methods: 30 orthodontic pre and post-treatment casts were measured using the PAR index. The cases used were all adolescents (Mean pretreatment age: 13.1 years, SD ± 1.6) Least squares analysis was used to test the empirical equation that percent decrease in PAR score is a function of treatment times, initial PAR score and gender.

Results: The computed F value for the empirical model is significant beyond the 0.05 alpha level and the R² value is 47%. Results show that controlling for gender and treatment time, initial PAR score significantly predicts percent decrease in PAR score.

Conclusion: Cases that are initially more severe derive greater benefit (in terms of severity reduction) from orthodontic treatment than less severe ones.