Thesis
Advanced assessment of forces during rapid maxillary expansion
University of Iowa
Master of Science (MS), University of Iowa
Spring 2026
DOI: 10.25820/etd.008445
Abstract
Objective
Maxillary transverse deficiency is a prevalent clinical condition often associated with dental crowding, functional mandibular shifts, posterior crossbites, and potentially asymmetric growth. Rapid maxillary expansion (RME) is commonly employed to correct this discrepancy by separating the midpalatal suture. However, few studies have quantified the forces generated during active expansion. This study aimed to establish a novel in vivo methodology for measuring expansion forces and to evaluate how maxillary anatomical characteristics influence the magnitude of forces and their transmission patterns.
Methods
Fifty-eight patients aged 7–16 years were treated with either two- or four-banded Hyraxstyle RMEs. Intermolar width and palatal height were recorded at baseline using 3Shape Ortho System software. Each appliance was calibrated prior to placement. Patients returned daily for two jackscrew activations over a 10–17-day period until transverse correction was achieved. Forces were recorded. Standardized intraoral photographs, midline diastema measurements, and digital scans were obtained at each visit, and maxillary occlusal radiographs were taken after active expansion. Expansion-resisting forces were calculated using appliance-specific calibration curves and compared with anatomical measurements before and after sutural separation.
Results
Preliminary results demonstrated expansion forces ranging from 0–20 lbs, with no consistent reduction in force after midpalatal suture separation, suggesting that resistance to expansion extends beyond the suture alone. Older patients (>13 years) exhibited higher overall expansion forces and steeper loading rates compared with younger patients. Patients with higher palatal vaults had greater force changes pre- and post-diastema formation. No significant differences in skeletal expansion were observed between two- and four-banded RMEs
Conclusion
Older patients demonstrated greater resistance and higher initial force accumulation during expansion, with resistance often persisting after visible diastema formation for all ages. Maxillary palate anatomy seems to influence force patterns during the expansion, while appliance banding configuration did not significantly influence skeletal outcomes.
Details
- Title: Subtitle
- Advanced assessment of forces during rapid maxillary expansion
- Creators
- Lyda Leigh Sypawka Madigan
- Contributors
- Kyungsup Shin (Advisor)Steven D. Marshall (Committee Member)Michael A. Callan (Committee Member)Lina Moreno Uribe (Committee Member)
- Resource Type
- Thesis
- Degree Awarded
- Master of Science (MS), University of Iowa
- Degree in
- Orthodontics
- Date degree season
- Spring 2026
- DOI
- 10.25820/etd.008445
- Publisher
- University of Iowa
- Number of pages
- x, 101 pages
- Copyright
- Copyright 2026 Lyda Leigh Sypawka Madigan
- Language
- English
- Date submitted
- 04/20/2026
- Description illustrations
- Illustrations, graphs, charts, tables
- Description bibliographic
- Includes bibliographical references (pages 92-100).
- Public Abstract (ETD)
Some children and teenagers have an upper jaw that is too narrow. This problem can cause dental crowding, crossbites, and shifts in how the lower jaw closes. Rapid maxillary expansion (RME) is a common orthodontic treatment used to widen the upper jaw. The appliance slowly opens a natural joint in the roof of the mouth, allowing the upper jaw to expand. Although this treatment has been used for many years, the forces created during expansion have not been well measured in patients.
This study developed a new way to measure the forces produced during rapid maxillary expansion in real patients. Fifty-eight patients between the ages of 7 and 16 received an expansion appliance. Jaw width, palate shape, and expansion forces were recorded during treatment.
Results showed that expansion forces varied widely among patients. Older patients tended to produce higher forces and showed greater resistance to expansion. The shape of the palate also influenced how forces changed during treatment. Interestingly, resistance often continued even after the midline gap between the front teeth appeared, suggesting that other facial structures also resist expansion.
These findings improve our understanding of how rapid maxillary expansion works. This knowledge may help orthodontists better predict treatment response and tailor expansion therapy to individual patients.
- Academic Unit
- Orthodontics
- Record Identifier
- 9985176975702771
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