Abstract

The purpose of this research was to determine if forward movement of the lower incisor in a horizontal plane during active treatment affected the post-retention stability. The post-active treatment position of the lower incisor in relation to APo plane, NB plane and mandibular plane was also studied to determine if it affected the post-retention stability.

To determine where the lower incisors were moved during treatment, the beginning cephalometric tracings were superimposed over the end of active treatment tracings on the Corpus Axis at Supra-Pogonion. The amount of change in the incisal edge was measured to the nearest millimeter on a plane exactly parallel to Frankfort Horizontal Plane.

Measurements were also completed from the beginning, end of active treatment and post-retention cephalometric tracings to determine where the lower incisor was positioned in relation to APo plane, NB plane, and mandibular plane. The study models of each patient were measured to determine the amount of pre-treatment and post-retention lower anterior arch length discrepancy. All linear measurement were made to the nearest millimeter and all angular measurements were to the nearest degree.

Four studies were made on the 78 patient sample with the following results: The first study determined that the movement of the lower incisor forward, leaving it near its original position or retraction during active treatment does not significantly affect stability after retention. Some cases were moved forward as much as 7 mm with very good post-retention stability.

The second study indicated the end of active treatment position of the lower incisor in relation to APo plane apparently does not affect post-retention stability. Cases which were finished with the lower incisor 4 mm ahead of APo plane provided very stable post-retention results.

The results of the third study determined that there was no post-retention effect on stability in relation to lower incisor to NB plane. The end of active treatment position of lower incisor was 9 mm ahead of the NB plane in some cases with no post-retention lower anterior crowding.

The post-treatment lower incisor to mandibular plane angle was also studied and the results indicated that it did not affect the post-retention stability. A case was finished with 113° IMPA with no post-retention crowding.

In the past many assumptions have been made about function and stability without giving esthetics much consideration. It has been shown in this research that the lower incisor can be positioned for ward during active orthodontic treatment without fear of relapse and much arch length can be gained. This can allow a better esthetic result in many cases as the need for extraction is greatly reduced.

LLU Discipline

Orthodontics

Department

Orthodontics and Dentofacial Orthopedics

School

Graduate School

First Advisor

James R. Wise

Second Advisor

Roland D. Walters

Third Advisor

Robert J. Schulhof

Fourth Advisor

Lloyd E. Gauntt

Fifth Advisor

Virgil V. Heinrich

Degree Name

Master of Science (MS)

Degree Level

M.S.

Year Degree Awarded

1975

Date (Title Page)

3-1975

Language

English

Library of Congress/MESH Subject Headings

Cephalometry; Dental Occlusion; Orthodontics

Type

Thesis

Page Count

ix; 57

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

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