Abstract

Since the introduction of bonded orthodontic brackets in the early 1960's spontaneous debonding has been a constant nemesis. Most attempts to avoid this problem by orthodontic manufactures have focused on "bond strength" issue. Whether they chose to address the materials, the bracket base or both, the common method used to evaluate improvements entailed the use of just one testing apparatus: a static universal testing machine such as the Instron.

Metal, ceramic and plastic bonded brackets were tested with the traditional shear/peel method as well as a new high strain rate impact test. The resin itself was also evaluated for physical and mechanical properties. This study introduces two new ways of evaluating orthodontic bonding systems. The first involves a high strain rate test method similar to Izod or Charpy impact testing. The impact test involves releasing a pendulum of known mass from a known height that dislodges bonded brackets. The bond strength is calculated by recording the difference between the starting height and the finishing height of the pendulum. The higher the bond strength, the lower the finishing height of the pendulum will be.

The second test involved evaluating the fracture characteristics of the bonding resin itself. For this test, a compact type fracture specimen was designed to evaluate crack propagation characteristics.

Our study found that bonded orthodontic brackets performed differently when tested with a low strain rate test as compared to high strain rate testing (p < .01). Finite element analysis showed that stress concentrations permit relatively light forces to cause resin fracture.

In conclusion, our study demonstrated that low strain rate testing itself is inadequate in understanding bonded bracket failure. With the introduction of a high strain rate test as well as fracture analysis, bonded bracket retention can be better understood.

LLU Discipline

Orthodontics and Dentofacial Orthopedics

Department

Orthodontics and Dentofacial Orthopedics

School

Graduate School

First Advisor

Craig A. Andreiko

Second Advisor

Joseph M. Caruso

Third Advisor

Eric Chapoulaud

Fourth Advisor

Willis L. Schlenker

Degree Name

Master of Science (MS)

Degree Level

M.S.

Year Degree Awarded

2000

Date (Title Page)

6-2000

Language

English

Library of Congress/MESH Subject Headings

Dental Bonding; Orthodontic Brackets; Dental Cements; Resins

Type

Thesis

Page Count

viii; 39

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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