Abstract

Introduction: Miniscrews are used in orthodontics as practical temporary anchorage devices (TAD's). The purpose of this animal study was to measure reverse torque values for Absoanchor 1.2 mm and Micerium 1.5mm miniscrews at 0, 2, and 12 weeks under loaded and unloaded conditions.

Methods: Ninety-six miniscrews were placed in the femora of twelve rabbits and allowed to heal for either two or twelve weeks. Half of the fixtures were loaded immediately with NiTi open coil springs producing a force of 150-200g and the other half served as unloaded controls. For each of the healing times, two and twelve weeks, seven to nine Absoanchor and Micerium miniscrews were reverse torque tested under loaded and unloaded conditions. Three additional fixtures for each test condition were harvested for histologic analysis in a subsequent study. Additionally, 84 Miscerium and 69 Absoanchor miniscrew fixtures were placed and immediately reverse torque tested for time zero weeks.

Results: All of the miniscrews were clinically immobile at uncovering and none of the miniscrews fractured. The highest torque removal values were observed at time 0 weeks, i.e. immediately (p < .0001). Reverse torque values for loaded and unloaded fixtures were not statistically significantly different. Compared to Absoanchor miniscrews, Miscerium miniscrews displayed higher torque removal values at time 0 weeks (p < .0001), but no statistically significant difference was observed after 12 weeks of healing.

Conclusions: Immediate loading is not contraindicated. Loading immediately may prevent disturbing the fixtures at a vulnerable time. Using a larger diameter miniscrew with more bony compression contributes to initial stability, but does not significantly increase resistance to removal after twelve weeks of healing. Based on this study, the bone healing response is unlikely to contribute to miniscrew fracture.

LLU Discipline

Orthodontics and Dentofacial Orthopedics

Department

Orthodontics and Dentofacial Orthopedics

School

Graduate School

First Advisor

Joseph Caruso

Second Advisor

Jay Kim

Third Advisor

Kitichai Rungcharassaeng

Fourth Advisor

David Rynearson

Degree Name

Master of Science (MS)

Degree Level

M.S.

Year Degree Awarded

2005

Date (Title Page)

12-2005

Language

English

Library of Congress/MESH Subject Headings

Dental Implants; Bone Screws; Orthodontic Anchorage Procedures

Type

Thesis

Page Count

ix; 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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