Abstract

Spontaneous debonding has proven a constant problem since the introduction of bonded orthodontic brackets in the early 1960's by Newman1.

Components in classic bond strength testing are the bracket, the adhesive, the adhesive curing method, the type of teeth used, and the test method. These tests lead to extensive and compounding variables that make it difficult to evaluate the performance of any of the components individually.

The purpose of this study was to compare several contemporary orthodontic bonding adhesives by testing the physical and mechanical characteristics of the adhesives alone. Material properties compared were sonic and tensile measurements of Young's modulus, elongation to failure, ultimate tensile strength, work of fracture, and crack initiation and propagation characteristics.

The characteristics of nine different bonding resins were examined. A standard tensile test used a dogbone shaped specimen to test the material's ultimate strength, elongation to failure, tensile modulus of elasticity and work of fracture. A compact type fracture specimen was used to evaluate crack initiation and propagation characteristics.

Finally, the density and the sonic velocity were also measured, and from these the sonic modulus was calculated. The resulting data was evaluated to determine which material might have physical advantages over the other for use as an orthodontic bonding material.

The combination of ultimate strength and elongation to failure is work of fracture. The results showed System 1+ to have an average work of fracture 40% greater than any other material tested while Lightbond's average ultimate strength proved to be 20% higher than any of the other materials tested.

Compact specimen fracture testing measures the amount of pin separation required to initiate a fracture in the material and its toughness in resisting crack propagation. In this evaluation, System 1+ had the highest resistance to crack initiation and propagation. It appeared that Eagle No Drift and Fuji LC had the lowest resistance to crack initiation and propagation.

The large discrepancy between the sonic and tensile modulus indicates that the glass reinforcement is only minimally helpful in tensile situations such as those found in bracket loading. The contribution of the filler to inhibiting crack propagation may, however, be substantial.

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1. Newman GV: Epoxy adhesives for orthodontic attachments. A progress report. Am J Orthod. 51:901-12. 1965.

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

Daniel A. Flores

Fourth Advisor

Jay S. Kim

Degree Name

Master of Science (MS)

Degree Level

M.S.

Year Degree Awarded

2001

Date (Title Page)

6-2001

Language

English

Library of Congress/MESH Subject Headings

Orthodontics; Dental Bonding; Dental Materials

Type

Thesis

Page Count

viii; 34

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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