Student Theses, Dissertations and Capstones

Document Type

Thesis - NSU Access Only

Degree Name

Master of Science (M.S.) in Dentistry

Copyright Statement

All rights reserved. This publication is intended for use solely by faculty, students, and staff of Nova Southeastern University. No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, now known or later developed, including but not limited to photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the author or the publisher.

Department

College of Dental Medicine

Publication Date / Copyright Date

2011

Publisher

Nova Southeastern University

Abstract

A thesis submitted to the College of Dental Medicine of Nova Southeastern University of the degree of Master of Science in Dentistry.

Objectives. The purpose of this study was to determine the effect of pitch and thread depth of orthodontic miniscrew implants(MSI's) on stress generation. Methods. Quasi-three dimensional photoelastic models were created with MSI's embedded and then loaded with 60 and 104 grams respectively and evaluated under a full field reflection polariscope. The control MSI's (1.0mm pitch / 0.25mm thread depth) were compared to 3 experimental groups (n=10) which varied with only one design characteristic: Group 1 (0.75mm pitch), Group 2 (1.25mm pitch) and Group 3 (0.40 thread depth). The maximum shear stress (τmax) was calculated at 5 predetermined and standardized points. A two-way ANOVA was conducted to compare the means of τmax followed by a Tukey's post hoc (p<0.05). Results. No statistical differences were found for τmax between the control group and each of the 3 experimental groups except at point 4. At point 4, the control group was higher by an average of 5.05 and 7.1 MPa for the 60 and 104 gram loads respectively (p<0.05). No statistically significant differences were found for points 1, 2, and 5 for the 60 gram load and for points 1, 2, 3, and 5 for the 104 gram load. The mean τ max from highest to lowest was located at points 5<1< 2<4 <3 in both the 60 and 104 load steps. The variability in τmax at point 4 may have been due to its proximity to the neutral zone of the present loading conditions. Conclusions. As the orthodontic load was increased, maximum shear stress also increased for each of the four MSI designs used in this study. The results of this study suggest that, within limits, variation of pitch and thread depth of MSI's may not have a significant influence on the stress generation when loaded for orthodontic purposes. Photoelastic analysis has shown to be a viable option to evaluate mechanical properties of MSI'S.

Disciplines

Dental Materials | Dentistry | Orthodontics and Orthodontology

Keywords

Health and environmental sciences, Communication and the arts, Applied sciences, Miniscrew implants, Photoelasticity, Stress generation, Temporary anchorage devices, Thread design

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