Quantitative Evaluation of the Mandibular Symphysis in Adults With Different Skeletal Severities
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Objectives: The mandibular symphysis plays an important role in determining the profile of the orthodontic patient. The aim of this cross-sectional cephalometric study was to evaluate the mandibular symphysis dimensions in adult orthodontic patients that present with different vertical and anteroposterior skeletal severities. Methods: 90 digital lateral cephalograms were selected from the records of untreated subjects presenting for treatment at the University at Buffalo School of Dental Medicine orthodontic department. The inclusion criteria were untreated subjects who were 18 years old or above, lateral cephlograms of high resolution and showing symphyseal region, sella-nasion and points A and B, and records taken between 2006 and 2014. The lateral cephalometric radiographs were traced then analyzed using Dolphin Imaging (Version 11.7). To determine the mandibular symphysis dimensions, a modified analysis from the studies of Suri et al (2006) and Chooryung Chung et al (2008) was used. The outcomes of interest were symphysis height, thickness, and ratio. The sample included 44 females and 46 males. The results were analyzed by gender. Results: For correlations in females, there was a statistically significant relationship between symphysis height and thickness with SNA angle. As well, there was a significant negative relationship between symphasis ratio and basal width. For correlations in males, there was significant relationship between symphysis height and gonial angle, between thickness and basal width and between thickness and gonion-nerve. There was also a significant negative relationship between thickness and gonial angle, between ratio and basal width and between ratio and gonion-nerve. Moreover, there was significant relationship between ratio and gonial angle. For the prediction model of the symphyseal height, Gonion-nerve and gonial angle were included in the model. For symphyseal thickness prediction model, basal width, Gonion-nerve and alveolar height were included. For height/thickness ratio, basal width and alveolar height were included. For females, SNA was included in the prediction model of height. Basal width and SNA were included in the model of the thickness. Basal width and alveolar height were included in the model of the ratio. For males, gonial angle was included in the model of height. Basal width was included in the model of thickness. Basal width and gonial angle were included in the model of the ratio. Conclusions: There was no significant correlation between the ANB values and the symphyseal height, thickness or ratio. Symphysis thickness, height and ratio of height/thickness are more related to gonial angle (vertical skeletal pattern) than ANB (anteroposterior pattern). Further studies are needed to evaluate gonion-nerve measurements in relation to the symphysis and in relation to anteroposterior skeletal pattern.