Student Theses, Dissertations and Capstones

Document Type

Thesis - NSU Access Only

Degree Name

Master of Science (M.S.) in Dentistry

Copyright Statement

All rights reserved. This publication is intended for use solely by faculty, students, and staff of Nova Southeastern University. No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, now known or later developed, including but not limited to photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author or the publisher.

Department

College of Dental Medicine

First Advisor

Abraham Lifshitz

Date of original Performance / Presentation

January 2013

Publication Date / Copyright Date

1-1-2013

Abstract

Objective: The objectives of this retrospective study were to establish a ratio between the upper incisor retraction and the upper lip retraction after orthodontic treatment, and to determine if there is a correlation between the upper lip thickness and the ratio of soft tissue response to incisor retraction. A comparison of the results was made between different ethnicities. Background: Previous studies have shown that orthodontic movement of the anterior teeth can significantly change the position of the lips. According to these articles, the change in position of the lips can be correlated to the antero-posterior position of the incisors. However, the reported correlations show a wide variation among patients, and many studies suggest that lip thickness and ethnicity may contribute to this variation. Materials and Methods: Initial and final orthodontic records of patients from Hispanic, White-American or African-American backgrounds treated with bilateral upper first bicuspid extractions were collected. All radiographs were uploaded and digitalized in Dolphin Digital Imaging software. Measurements were made on the initial and final cephalometric radiographs, including: 1) the antero- posterior position of the upper incisors, 2) the inclination of the upper incisors related to the anterior cranial base, 3) the antero-posterior position of the upper lip, and 4) the upper lip thickness. Results: Significant differences were found between the initial and final thickness of the upper lip after incisor retraction. There were no differences between the upper lip/upper incisor retraction ratios amongst ethnicities. The initial lip thickness showed a strong correlation with the retraction ratio and demonstrated to be a good predictorfor lip response. Conclusions: The lip becomes thicker after retraction of the upper incisors. There is no significant difference between the lip response amongst ethnicities. However, the ratio is higher for White American patients. In this sample, thicker lips responded less to tooth movement.

Disciplines

Dentistry

Keywords

Ethnicity; Incisor Retraction; Lip thickness; Retraction Ratio

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