In the practice of orthodontics much time is spent each week replacing broken appliances. However, very little research has been done to study the cause of orthodontic wire failure. A few articles have reported the incidence of removable appliance failures but only one article has reported research concerning the failure of fixed appliance wires.

There has been much speculation concerning the contributing factors for premature wire failure. The concensus is that fatigue is a major factor in their fracture. There are three basic types of wire failure: ductile, fatigue, which ends in ductile rupture, and brittle failure. Ductile failure is characterized by microvoids in a photomicrograph. Fatigue is characterized by striations on the fracture surface and brittle failure leaves river marks.

The purpose of this study is to show that wire fatigue is a major factor in the failure of orthodontic archwires by illustrating striations on the fractured surfaces.

Forty-eight specimens of intra-orally fractured archwires were collected and mounted for viewing in the scanning electron microscope. Twenty-five of the specimens were randomly chosen for viewing. Fourteen of them were soft-temper cobalt-chromium and eleven were stainless steel. Photomicrographs were taken of the scanned fracture surfaces.

Twenty-two of the specimens illustrated fatigue striations. It is possible that the others also failed by a fatigue mechanism even though no striations were evidenced. There were no signs of brittle failure noted in any of the specimens.

The results indicate that fatigue is the initiating factor in the premature failure of orthodontic archwires. Steps can now be taken to reduce the incidence of fractured wires in the orthodontic practice. These steps should include the following:

  1. Reduction of the number of bends placed in an archwire.

  2. Replacement of worn pliers.

  3. Avoidance of sharp bends in the archwire.

  4. Minimization of traumatic occlusal interferances.

LLU Discipline





Graduate School

First Advisor

Jack L. Tomlinson

Second Advisor

Roland D. Walters

Third Advisor

John K. Pearson

Fourth Advisor

Clelan G. Ehrler

Fifth Advisor

Gary G. Morikone

Degree Name

Master of Science (MS)

Degree Level


Year Degree Awarded


Date (Title Page)




Library of Congress/MESH Subject Headings

Orthodontic Appliances



Page Count

vi; 37

Digital Format


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.


Loma Linda University Electronic Theses and Dissertations

Collection Website



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