Thesis
A novel approach for measuring resistance to Hyrax rapid maxillary expansion: a pre-clinical study
University of Iowa
Master of Science (MS), University of Iowa
Spring 2022
DOI: 10.25820/etd.006438
Abstract
Introduction Maxillary constriction is often associated with posterior crossbites, functional shifts, maxillary crowding, and asymmetric jaw growth. The current standard of care for treating a constricted maxilla is rapid maxillary expansion (RME), which uses high levels of force to separate the midpalatal suture. However, few studies have attempted to estimate the forces produced by RME appliances. The purpose of this study is to develop a novel method of evaluating the resistance to Hyrax expansion.
Materials and Methods
Five Dentaurum Palex® Maxi 12mm expansion screws were acquired for testing, and a separate expansion key was fabricated for each screw. An apparatus was fabricated to allow measurement of the force required to turn an expansion screw when subjected to defined loading conditions. Each screw was tested under thirteen loading conditions for each of four situations: unmodified, with reduced friction, with bent arms, and soldered into an expander appliance. The forces measured in these situations were compared statistically.
Results
A statistically significant difference in the turning force existed between the initial and frictionless situations when loading was below 5000g, between the frictionless and bent situations when loading reached 2000g or higher (except the 4000g load), and between the bent and soldered situations when loading was unmodified (0g). Although Spearman’s rank coefficients (r) indicated no correlation between loading condition and force in the initial situation for two of the five expanders (r=0.24, p=0.437; r=0.21, p=0.494), there was significantly strong correlation in the initial situation for the other three expanders (r=0.84-0.99, p<0.05 in each instance). There was also significantly strong correlation between loading condition and force for all five expanders in each of the other three situations (frictionless, bent, and soldered).
Conclusions
Under the conditions of this experiment, we conclude the following: Friction is a confounding factor when measuring the forces resisting expansion of the screw. Frictional forces resisting expansion vary between individual screws. Bending an expansion screw into a clinical configuration affects the force levels needed to turn the screw. Soldering an expansion screw to fabricate an expansion appliance may have an effect on the force levels needed to turn the screw. Based on these findings, recommendations for using this method are given. This novel pre-clinical measurement approach will be translated to a clinical pilot study with orthodontic patients.
Details
- Title: Subtitle
- A novel approach for measuring resistance to Hyrax rapid maxillary expansion: a pre-clinical study
- Creators
- Jayne Alyda Kessel
- Contributors
- Kyungsup Shin (Advisor)Thomas E Southard (Committee Member)Steven D Marshall (Committee Member)Michael A Callan (Committee Member)Fang Qian (Committee Member)
- Resource Type
- Thesis
- Degree Awarded
- Master of Science (MS), University of Iowa
- Degree in
- Orthodontics
- Date degree season
- Spring 2022
- DOI
- 10.25820/etd.006438
- Publisher
- University of Iowa
- Number of pages
- x, 72 pages
- Copyright
- Copyright 2022 Jayne Alyda Kessel
- Language
- English
- Description illustrations
- color illustrations
- Description bibliographic
- Includes bibliographical references (pages 67-72).
- Public Abstract (ETD)
A narrow upper jaw can cause problems such as dental crowding, a poor bite, and growth asymmetries. It is most commonly treated by an orthodontist with an expander, which is attached to the upper teeth and pushes the two halves of the upper jaw apart to make it wider.
The purpose of this study was to evaluate how difficult it is to expand the upper jaw; that is, how much force it takes to push the jaw apart. A machine was constructed that can measure the forces it takes to make an expander widen, and five expanders were tested in the machine.
By testing these expanders, a method was developed that can be used in the future to measure how much force it takes to widen the jaw in real patients. This method can be used to determine whether it is more difficult to widen the upper jaw in patients of different ages and sexes.
- Academic Unit
- Orthodontics; Craniofacial Anomalies Research Center
- Record Identifier
- 9984271055602771
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