Which are the most valuable predictor parameters in PAR index

One of the most popular indexes used in Orthodontics is the Peer Assessment Rating (PAR) index. Objectives: to find the combination of the minimum number of parameters in the PAR index that can predict or explain at least 80% of the final PAR score. Materials and Methods: Sixty study models of 30 pairs of siblings, mean age of 12.2 + 1.6 years representing different malocclusions were randomly selected from our archive in the IDF orthodontic department. All models were analyzed and scored using the original PAR index. A forward Stepwise Regression statistics analyzed all 11 parameters for the total group and for 26 individuals with mixed dentition (MD) and 34 individuals with permanent dentition (PD). Results: 81.5% of the PAR score variation for the whole group was explained by 4 parameters – Upper anterior segment (UAS), Upper right and left segments (URS and ULS) and Lower right segment (LRS). In the MD group the combination of UAS, URS, LRS and Right buccal occlusion (RBO) could explain 82% of the PAR score, while in the PD group the UAS, URS and ULS and Lower anterior segment (LAS) could explain 85% of the final PAR score, all with statistical significance (P<0.001). Conclusion: It seems that crowding in different segments rather than buccal occlusion (Angle classification), overjet and overbite have the main contribution to the final PAR score.