Abstract

Closed helix retraction springs fabricated from .016 X .016 inch Blue Elgiloy, Permachrome Standard stain less steel, and Multiphase orthodontic wire were tested at 37°C in their heat and nonheat treated condition to determine force relaxation properties. Electronic equipment consisting of load cells, regulated power supply, and an automatic recording device were used to measure force changes which occurred in the wire samples over a seven day period. A constant temperature was maintained by an ethylene glycol and water circulator. A temperature probe and an electronic thermometer monitored the 37°C water bath surrounding the wire samples. The data was graphed showing the force changes as well as temperature variation above and below 37°C. The data were also statistically analyzed by computer to determine the means, standard deviations, and analysis of variance.

The results of this study indicate that between 60- 97% of the mean force loss occurred within the first 24 hours for the three types of wires in their heat and non heat-treated condition. Most of the force relaxation occurred after the one week period.

Nonheat-treated Blue Elgiloy, Permachrome Standard, and Multiphase had very similar force relaxation properties when activated with 150 grams of force. They had a mean force loss at the end of seven days of 3.5%, 4%, and 4% respectively.

Heat treated Permachrome Standard had 50% less force loss than did nonheat-treated. It also had the least mean force loss values of all the wires tested. Heat-treated Blue Elgiloy had the highest mean force loss, 11.5 grams or 7-7%, at the end of seven days. The maximum mean force loss recorded within the seven days was also heat-treated Blue Elgiloy with 14.8 grams or 10% loss. Of the 36 wire samples tested one sample of Blue Elgiloy heat-treated lost 27.5 grams or 18.3% of its initial activation.

Excessive temperatures during heat treatment of Blue Elgiloy and Multiphase was the most probable reason for the unpredicted increase in force loss as compared to the nonheat-treated condition. When Blue Elgiloy and Multiphase are heat treated at 1200°F for 5 minutes, and 900°F for 30 minutes respectively, excellent force loss properties that are similar to Permachrome Standard result. This indicates that unless heat-treatment is done properly it is better not to heat-treat orthodontic wire. If it is properly heat treated less force loss will occur.

LLU Discipline

Orthodontics

Department

Dentistry

School

Graduate School

First Advisor

James R. Wise

Second Advisor

Grenith J. Zimmerman

Third Advisor

Donald S. Schmitt

Fourth Advisor

Joseph M. Caruso

Fifth Advisor

Laurence A. Seifert

Sixth Advisor

Earl R. Crane

Degree Name

Master of Science (MS)

Degree Level

M.S.

Year Degree Awarded

1982

Date (Title Page)

2-1982

Language

English

Library of Congress/MESH Subject Headings

Orthodontic Appliances

Type

Thesis

Page Count

ii; 52

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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