Improvement in Peer Assessment Rating scores after nonextraction, premolar extraction, and mandibular incisor extraction treatments in patients with Class I malocclusion

•Improvements in occlusal characteristics were comparable in NE, PME, and MIE treatments.•We found significant differences in posttreatment PAR scores between NE and MIE groups, and PME and MIE groups.•Comparable differences in pretreatment PAR scores depicting occlusal outcome may be related to the severity of the original malocclusion.

IntroductionDifferent treatment protocols implemented for correction of Class I malocclusion aim at achieving ideal occlusal characteristics. This study was planned to evaluate the improvement in the occlusal characteristics of Class I patients treated with nonextraction (NE), all first premolar extractions (PME), and mandibular incisor extraction (MIE) as assessed by the percentage of improvement in Peer Assessment Rating (PAR) scores.MethodsThis retrospective cross-sectional study was conducted on the pretreatment and posttreatment dental casts of 108 subjects with Class I malocclusion. The total sample was divided into 3 equal groups according to the treatment protocol implemented: NE, PME, and MIE. The mean pretreatment and posttreatment PAR scores, and the percentages of improvement were compared among the 3 treatment modalities using Kruskal-Wallis and post-hoc Dunnett T3 tests.ResultsThe mean percentages of improvement in the PAR score were 75.8% ± 25.8% in the NE group, 73.1% ± 19.4% in the PME group, and 70.6% ± 24.1% in the MIE group. There was no significant difference (P = 0.351) in the percentages of improvement in PAR scores among the 3 treatment modalities. However, the mean pretreatment and posttreatment PAR scores varied significantly (P <0.001) in the 3 groups. The average pretreatment and posttreatment PAR scores were highest in the MIE group and lowest in the NE group.ConclusionsThe comparable percentages of improvement in PAR scores among the 3 groups denote that equivalent occlusal corrections were achieved in Class I patients treated with the NE, PME, and MIE protocols.