Comparison of Incisor Inclination in Extraction and Non-extraction Orthodontic Patients

Contemporary orthodontic treatment of malocclusion may involve tooth extraction or expansion of the dental arches without extraction. Objectives: The aim was to compare incisor inclination in finished cases treated with extractions with cases treated non-extraction. Method: Orthodontic cases were selected from an archival database and divided into the following groups: Class I non-extraction, Class I extraction, Class II non-extraction, and Class II extraction. Inclusion criteria were caucasians with 2 maxillary and 2 mandibular premolar extractions. Angular measurements of the maxillary incisors to sella-nasion (MaxInc), mandibular incisors to mandibular plane (MandInc), and the inter-incisal angle (IntrInc) were made on both pre- and post-treatment cephalograms. Intra-rater reliability was high (intra-class correlation coefficients > 0.90). Final incisor inclination as well as change in inclination following orthodontic treatment were evaluated. The mean values of each group were then compared using ANOVA and the Tukey-Kramer test. Results:

Conclusions: (1) Extraction resulted in more upright maxillary incisors in both Class I and Class II cases; (2) non-extraction resulted in more proclined mandibular incisors in both groups; and (3) the interincisal angle decreases in both of the non-extraction groups and increases in the extraction groups.