Abstract: Objective: To investigate the orthodontic treatment outcome of anterior deep overjet patients with congenital hypodontia of a mandibular central incisor using PAR index. Methods: This retrospective study included thirty-six deep overjet patients with congenital hypodontia of a mandibular central incisor. Eighteen patients who extracted maxillary first premolars were in group A. Other eighteen patients who extracted maxillary first premolars and a mandibular premolar were in group B. Group A and B were measured and analyzed according to the PAR indexs and cephalometrics before and after orthodontic treatment. Results: The difference in the weighted PAR scores and each of the PAR scores were statistically significant (P<0.01). There were significant changes in posterior occlusal relationship (P<0.05) and midline (P<0.01) in group B. Conclusion: Extraction of two maxillary premolars and one mandibular premolar could achieve more satisfactory occlusal relationship to anterior deep overjet patients with congenital hypodontia of a mandibular central incisor.

Key words: Anterior deep overjet , Congenital hypodontia of mandibular central incisor , Extraction models , Peer assement rating index , Cephalometric analysis