Abstract

The purpose of this study was to Investigate and compare the plastic or permanent deformation of different commercially available aesthetic polymer brackets (American, Ormco, GAC and RMO). It also examined the effect of tying the bracket wings with a wire ligature as well as the effect of thermocycling on the permanent deformation of these brackets.

Seven brackets of each type were tested In each of the three following conditions; group 1; tied with a wire ligature and loaded, group 2; thermocycled and loaded, and group 3: loaded only, with a total of 84 brackets tested. Each bracket was bonded to a metal mesh pad which was tack welded to a solid stainless steel ring. The assembly was then placed under a loading device. This loading device, used In a previous study22, removes variables such as bond adhesive strengths, and torsion of a wire used to deform the bracket slot. The bracket slot was loaded by the application of a biaxial load In order to produce a wedging force to deform the wings of the bracket. The bracket slot was placed In this loading frame for a period of 24 hours using 2,000 grams of force. The bracket slot was then measured under a video enhanced measuring microscope at three time intervals; before loading, after 24 hours of loading, and finally 24 hours after being released from the load. The measurements were then compared at the different time intervals within each group and between the different groups.

There was a statistically significant difference in the permanent deformation of the four types of brackets tested, from the preloaded to the loaded brackets and 24 hours after being released from the load. The polycarbonate brackets with no reinforcement showed the most deformation and was significantly different than the other polycarbonate brackets that were reinforced with either a metal slot or with a ceramic filler. There was however no statistically significant difference in the amount of permanent deformation between the different groups. Therefore, the wire ligature and the thermocycling did not affect significantly the permanent deformation of these polycarbonate brackets.

LLU Discipline

Orthodontics

Department

Orthodontics and Dentofacial Orthopedics

School

Graduate School

First Advisor

M. Toufic Jeiroudi

Second Advisor

Daniel A. Flores

Third Advisor

Carlos Munoz

Fourth Advisor

Willis Schlenker

Degree Name

Master of Science (MS)

Degree Level

M.S.

Year Degree Awarded

1997

Date (Title Page)

6-1997

Language

English

Library of Congress/MESH Subject Headings

Orthodontic Brackets; Orthodontic Appliances

Type

Dissertation

Page Count

vi; 2; 35

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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