Assessment of relationship between ramus height and mandibular plane angle in long face patients

Abstract

The improvement of facial appearance had often been an objective common of orthodontic treatment and orthognathic surgery. Vertical problems are one of the main groups of skeletal deformities. Patients with long faces have characteristic facial appearance, including an increased mandibular plane angle and lower anterior facial height (LAFH), gummy smile and skeletal open bite. These features are often related together that correcting one of them may improve other features, too. But in patients with ramus dysplasia common treatment plans of vertical deformities wouldn't have an effect on improvement of ramus dysplasia. So it offers that ramus dysplasia may not accompanied with vertical problems. The aim of the present study was to evaluate how ramus height correlates with mandibular plane angle, according to the contradictions in references about this issue, and find the probable relation of ramus dysplasia with long face pattern by comparison of characteristics of non long face high angle patients with typical long face patients. Methods and material: In this study lateral cephalometric data of 102 high angle patients with mandibular plane angle of more than 37, from 8 to 40 years of age were used and chephalometric parameters of them were measured. First the correlation between ramus height and mandibular plane angle calculated. According to ratio of lower to total facial heights, with norm of 55%2%, the samples were classified as 2 subgroups: 1. High angle and LAFH/TAFH ratio less than 58% (non long face) 2. High angle and LAFH/TAFH ratio more than 60% (long face) Samples with LAFH/TAFH ratio of between 58-60% eliminated from survey. All data were analyzed statistically and compared between the groups. Results: Regarding to correlation coefficient of -0.130, there was no correlation between ramus height and mandibular plane angle. There was also significantly difference of parameters such as upper and lower gonial angle, ramus height, mandibular plane angle(MP-FH), inclination angle, anterior maxillary height, LAFh, TAFH, PFH, ramus/corpus ratio, LAFH(straight line), TAFH(straight line), LAFH/TAFH ratio, LAFH/TAFH ratio(straight line) between 2 subgroups. Conclusions: Patients with short ramus should be categorized as a distinct group of high angle classification. It seems appropriate to design studies in order to better define their morphological properties.