Abstract

The purpose of this study was to compare the fracture strength of ceramic brackets which are currently on the market with ceramic brackets tested in a previous study at Loma Linda. Fracture strengths of standard edgewise ceramic brackets vs. pre-torqued ceramic brackets and bicuspid ceramic brackets vs. central incisor ceramic brackets were also compared.

A total of 160 Polycrystalline brackets, 8 categories in groups if 20, were tested for fracture strength. Each bracket was tested using the same testing model that was used in the previous study at Loma Linda. The brackets were tested by torquing a wire within the bracket slot until a fracture occurred. An Instron machine was used to apply the force and record the fracture load value for each bracket. The fracture load value, recorded in pounds, was then converted to stress, recorded in pounds per square inch.

Results showed significant differences in load values for the following: 1) New vs. Old; type 2 new brackets had higher load values, and type 1 new brackets had lower load values. 2) Type vs. Type; type 1 brackets had the highest load values followed by type 2, followed by types 3 and 4. Types 3 and 4 were statistically equal 3) Torqued vs. Non-torqued; type 1 pre-torqued brackets had higher load values, and type 2 non-torqued brackets had higher load values. 4) Central vs. Bicuspid; for both types 3 and 4 the bicuspid brackets had higher load values.

Since all brackets tested are made from high purity alumina doped with less than .2 wt % MgO with about the same grain size, differences in load values may be attributed to variations in design, dimensions, and surface condition.

An analysis of stress measurements showed brackets of all four bracket types (with the exception of 3-PC-T) to fall within an acceptable range of 30-35 thousand psi. Therefore, although the statistics showed there are differences between the categories tested, for all practical purposes the strength of the material was the same for all brackets tested in this study and in the previous study by Flores16.

This study showed that although differences in load and stress values were statistically significant, they may not be clinically significant. There will not be a clinically significant change in the fracture strength of ceramic brackets until either design or the material used to make the brackets are changed.

LLU Discipline

Orthodontics

Department

Dentistry

School

Graduate School

First Advisor

Daniel A. Flores

Second Advisor

Joseph M. Caruso

Third Advisor

Garland E. Scott

Fourth Advisor

Norman S. Carter

Fifth Advisor

M. Toufic Jeiroudi

Degree Name

Master of Science (MS)

Degree Level

M.S.

Year Degree Awarded

1991

Date (Title Page)

6-1991

Language

English

Library of Congress/MESH Subject Headings

Orthodontic Appliances; Ceramics; Dental Stress Analysis

Type

Thesis

Page Count

2; iii 26

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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