Mandibular plane extremes and their respective anterior facial height
Nielsen, Briklin Owen
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Background: The diagnosis of a high or low mandibular plane angle (MPA) influences orthodontic mechanics. Research has tried to show relationships between the anterior facial height (AFH) and the MPA. Purpose: The purpose of this project is to compare different mandibular plane extremes with their respective AFH. Usually one would predict that with a high MPA the respective AFH would be increased. Our hypothesis is that there is no relationship between long and shorter face individuals and their respective MPA. Another question we hope to research is, are high or low MPA individuals more prone to having a deep and/or open bite? Research Design: Pre-treatment lateral cephalometric x rays were analyzed on adult patients. Measurements will be collected from two lateral cephalometric groups: high mandibular plane angles (SN-MP?38.0 degrees) and low mandibular plane angle cases (SN-MP<26.5 degrees). The following data was collected for both groups: Patient ID, Date of Birth, Initial Record Date, Gender, Ethnicity, MPA, Total Anterior Facial Height (TAFH), Upper Anterior Facial Height (UAFH), Lower Anterior Facial Height (LAFH), and LAFH Ratio, and Overbite (OB). Results: 97% of all high and low MPA patients had a normal or decreased TAFH. 98.7% of low MPA patients had a relative decreased TAFH. As the UAFH increased so did the proportion of those with high MPA. Despite having a high MPA 33.5% still had a decreased LAFH. The majority of high and low MPA patients had a relative normal LAFH ratio. There is so significant difference between the degree of OB and whether the patient has a high or low MPA. Conclusions: It remains difficult to compare the differences between high and low MPA and their respective anterior facial heights. Low MPA individuals tended to have a decreased TAFH, normal UAFH, decreased LAFH, and a normal LAFH ratio. High MPA individuals tended to have a decreased TAFH, normal UAFH, normal LAFH, normal LAFH ratio. There is no significant difference between overbite and its relationship to mandibular plane angle.