Student Theses, Dissertations and Capstones

Document Type

Thesis

Degree Name

Master of Science (M.S.) in Dentistry

Department

College of Dental Medicine

First Advisor

Lin, Chin-Yu

Publication Date / Copyright Date

12-2015

Publisher

Nova Southeastern University

Abstract

Introduction: One factor that contributes greatly to the lower face appearance and orthodontists have the ability to affect is lip profile. Clinical assessment of the lip profile is an important element in the decision of orthodontic treatment planning and in the evaluation of treatment progress and outcome. Three known factors influence the lip profile; the lip thickness, the underlying bone, and the tooth position. The positions and inclinations of the anterior teeth can affect the lip position, but it is unclear whether orthodontic brackets bonded to the labial surface of anterior teeth move the lip position and thereafter change the lip profile. Therefore, it is necessary to determine if orthodontic brackets bonded to the labial surface of the anterior dentition have any impact on lip profile. Objective: The objective of this project was to determine the effect that bonded brackets have on lip profile utilizing a standardized lateral photographic cephalogram analysis during the bonding and debonding stages. Methods: To determine the effect of bonded brackets on lip profile, digital photographic cephalometry was used. The patient was seated against a white backdrop in the standardized natural head position. Photographs were taken 5 feet from the patient, centered and level with the middle of the tragus of the right ear and were digitally analyzed using Dolphin Imaging software. Photos were acquired from 4 time points: before bonding (BT0) and after bonding (BT1) for the bonding group, and before debonding (DT0) and after debonding (DT1) for the debonding group. Upper and lower lip to E-plane, subnasale and lower lip to H-Line, superior sulcus depth, nasolabial angle, Z angle, upper and lower lip protrusion, and upper and lower lip to S-line were measured and analyzed statistically. The correlation of tooth angulation, lip thickness (determined using existing cephalometric radiographs), and bracket thickness on effect of lip position was also determined. Results: There are significant differences in all measurements of the lip profile, except superior sulcus depth and nasolabial angle, between BT0 and BT1 at the bonding stage. In the bonding stage, change in Z angle was correlated to initial lower lip thickness and change in upper lip protrusion was correlated to the initial upper lip thickness at the vermilion boarder and upper incisor bracket thickness. There was no significant difference noted between DT0 and DT1 at the debonding stage. Conclusion: Brackets have a significant effect on lip profile when bonding labial orthodontic brackets. Brackets have no significant effect on lip profile when debonding brackets. Therefore, a direct clinical assessment of lip profile before debonding is valid with no interference imposed by bonded orthodontic brackets.

Disciplines

Dentistry

Keywords

Health and environmental sciences, Bonding, Brackets, Debonding, Lips, Orthodontics, Profiles

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