Date of Award
Objective: As orthodontic treatment planning has evolved throughout its history, there has been an increased emphasis on the facial soft tissues. Little has been done to study the effects that proclination of the incisors has on the soft tissue profile. The purpose of this study was to 1) determine if there are significant changes of lip projection and shape with proclination of incisors, and 2) determine if there are significant associations between the movement of the hard and soft tissues after proclination of the incisors. The null hypothesis is that there is no statistically different changes and associations between hard tissues and soft tissues after orthodontic proclination of incisors. Materials and Methods: Twenty-eight adult patients treated at MUSoD with pretreatment upper incisor to SN angulation one standard deviation less (< 97.3°) than normal were chosen for this study. Exclusion criteria included craniofacial abnormalities, incomplete records, and patients treated with extractions. Pretreatment and posttreatment cephalograms were traced using the customized Marquette/Liu analysis on Dolphin Imaging. Paired t-tests and Pearson correlations were run using SPSS statistical software at a significance of p < 0.05. Results: All data were presented as mean ± SD. After orthodontic treatment there were statistically significant changes observed for upper lip length from subnasale to stomion (+1.228 mm ± 1.666 mm, p < 0.05), upper lip length from subnasale to stomion perpendicular to Y line (+1.128 mm ± 1.502 mm, p <0.05), lower lip thickness (-1.253 mm ± 2.006 mm, p < 0.05), and labiomental sulcus (-4.342 degrees ± 8.733 degrees, p < 0.05). There was no statistically significant change to skeletal structures A point and B point after proclination of upper incisors. Multiple dental tissue specific parameters had statistically significant change with proclination of the incisors (p < 0.05). Significant correlations could be drawn between movement of the skeletal/dental structures and the soft tissues (p < 0.05).