Award Date

5-1-2020

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Dental Medicine

First Committee Member

Brian Chrzan

Second Committee Member

Joshua Polanski

Third Committee Member

Tanya Al-Talib

Fourth Committee Member

Debra Martin

Number of Pages

146

Abstract

The aim of this study is to gather and analyze data representing detailed changes in model and cephalometric variables that will support clinicians in the premolar extraction decision- making process during camouflage treatment of class II dental patients. It is expected that the models, as measured by intra-arch dimensions, overjet, overbite, and mandibular crowding, and cephalometric radiographs, evaluated by their anteroposterior skeletal discrepancy, incisor inclinations, dental and skeletal vertical positions, and soft tissue characteristics, will significantly differ from within the same treatment group, pre-treatment to post-treatment, and between treatment groups. This retrospective study evaluated the model and cephalometric changes in a total of 74 subjects, with 33 subjects in group 1, who received extraction of maxillary first premolars as part of their comprehensive orthodontic treatment, 27 subjects in group 2, who received extraction of maxillary and mandibular first premolars, and 14 subjects in group 3, who received extraction of maxillary first premolars and mandibular second premolars. Intra-arch dimension at the canines, premolars, and molars for both upper and lower arches, overbite, overjet, and mandibular crowding were measured on digital models on OrthoCAD or OrthoAnalyzer software. Digital cephalometric radiographs were traced on Dolphin and analysis included SNA (°), SNB (°), ANB (°), Wits (mm), maxillary incisor inclination (U1-SN) (°), maxillary incisor protrusion (U1-NPog) (mm), mandibular incisor inclination (IMPA) (°), interincisal angle (U1-L1) (°), mandibular plane angle FMA (MP-FH) (°), anterior facial height (mm), posterior facial height (mm), upper lip to E-plane (mm), lower lip to E-plane (mm), nasolabial angle (°), soft tissue convexity (°), upper lip thickness (mm), and lower lip thickness (mm). The varying premolar extraction patterns do have a significant impact on the model and cephalometric characteristics, both within treatment groups and between treatment groups. All three treatments successfully and significantly reduced the amount of overjet and mandibular crowding. Extraction of maxillary and mandibular first premolars allowed a greater amount of mandibular crowding to be relieved. Nonextraction in the lower arch significantly increased the degree of lower incisor flaring. Inclusion of a larger patient population in future studies would allow the collection of more definitive and detailed documentation to identify exactly how removal of different premolars affect skeletal, dental, and soft tissue esthetics.

Keywords

Model and cephalometric variables; Premolar extraction decision- making process; Class II dental patients

Disciplines

Dentistry

File Format

pdf

File Size

5.5 MB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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