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Advisory Committee Chair

Nada Souccar

Advisory Committee Members

Chung H Kau

Nada Souccar

Amjad Javed

Yung-Tsung Hsu

Document Type

Thesis

Date of Award

2016

Degree Name by School

Master of Science (MS) School of Dentistry

Abstract

A STUDY OF THE RELATIONSHIP BETWEEN NASION PERPENDICULAR AND THE TRUE VERTICAL LINE JEFFREY ALBERT SHELLEY JR. DEPARTMENT OF ORTHODONTICS ABSTRACT The purpose of this study is to assess the relationship between Nasion perpendicular and the true vertical line between patient groups using cephalometric analysis. Materials and Methods: Ninety-six adolescent patients comprised the sample for this study. Subjects were between 10 and 18 years old, with no major craniofacial deformity. Three groups of patients were divided in to three groups (Class I, Class II and Class III) based on their skeletal antero-posterior relationship. Pre-treatment lateral cephalometric radiographs were taken with the Orthoceph® OC100 D. Using Dolphin ImagingTM software, the necessary anatomic landmarks were located and points were plotted. The angular difference between Nasion perpendicular and the true vertical line was calculated for the sample, and differences described between the different patient groups (Class I, II, and III). Results: Malocclusion class has a significant effect on the VFA (p<0.05). All three groups showed a mean negative angle, becoming more negative from Class II (-0.21º), to Class I (-2.1º), to Class III (-3.8º). In post-hoc tests, significant differences were observed between every class. Greater significance was displayed when comparing Classes I and III versus Class II, with much less significance between Class I and Class III. The difference between II and III was the most significant (-3.8º vs -0.21º). Conclusions: The anteroposterior jaw relationship does have a significant effect on the VFA when observed between Class I, II, and III groups. When the VFA differs significantly from the mean, measurements using NaPerp as a reference line will often indicate an unrealistic U1 position. The differences among different skeletal malocclusions must be taken into account when using the vertical reference plane NaPerp to assess U1 position. Keywords: Cephalometrics, Nasion perpendicular, True Vertical line

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