Abstract

Magnetic resonance imaging (MRI) is an essential diagnostic tool in modern medicine. Conditions such as cerebral vascular accidents, epilepsy and other seizure disorders, autism, cancer, migraine and cluster headaches benefit from its use. It has been discovered that 4-10% of all children and adolescents will experience a seizure at some point (Hauser, 1994) and MRI is one of the most common imaging modalities for seizure and epilepsy diagnosis. Unfortunately, some orthodontic materials cause distortion on MR images. Radiologists would probably require the removal of any distortion-causing orthodontic appliance prior to MR imaging. It is questionable whether radiologists would be comfortable diagnosing an abnormality of the brainstem when there is significant distortion of the nasopharynx on the MRI.

The purpose of this study was to evaluate the degree of craniofacial MR distortion caused various orthodontic brackets. It was hypothesized that stainless steel brackets would cause the most distortion followed by titanium, ceramic, and then plastic. Ten subjects received five different MRI scans. A control scan was conducted with Essix® trays fitted over the maxillary and mandibular teeth. Four experimental scans consisted of plastic, ceramic, titanium, and stainless steel brackets incorporated into Essix® tray material. Each of the five scans consisted of four different image modalities or sequences; namely, a T1 sagittal, T2 axial, gradient echo (GRE) and diffusion weighted (DWI) sequences. Three board certified neuroradiologists read the images and predetermined regions of the head were evaluated for distortion.

The study showed that the plain Essix® trays, plastic, ceramic and titanium brackets caused minimal distortion of the images. Stainless steel brackets generated significant distortion, rendering several cranial regions non-diagnostic. Areas with the most distortion were the body of the mandible, hard palate, base of the tongue, globes, nasopharynx, and frontal lobe. Statistical significant difference was demonstrated with a p < 0.0001. In general, the closer the stainless steel material was to the anatomical landmark the more distortion it caused. Additional scans were performed comparing 18-8 and 17-4 stainless steel and it was determined that 17-4 stainless steel causes the distortion. The brackets used in this study were composed of both.

Many of our orthodontic patients will require a head and neck MRI at some time during treatment. For those patients it would be best to avoid 17-4 stainless steel orthodontic appliances.

LLU Discipline

Orthodontics

Department

Dentistry

School

Graduate Studies

First Advisor

V. Leroy Leggitt

Second Advisor

Craig Andreiko

Third Advisor

James Farrage

Fourth Advisor

Udo Oyoyo

Fifth Advisor

Matthew Thomson

Degree Name

Master of Science (MS)

Degree Level

M.S.

Year Degree Awarded

2006

Date (Title Page)

9-2006

Language

English

Library of Congress/MESH Subject Headings

Orthodontic Appliances; Orthodontic Brackets; Magnetic Resonance Imaging -- adverse effects

Type

Thesis

Page Count

xi; 116

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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