title: A novel method for evaluating forces present during rapid maxillary expansion treatment
title: a clinical study
titleType: Subtitle
Creators: name: Wright, Daniel Victor
Publisher: name: University of Iowa
Year: 2024
Subjects: Expansion
Rapid maxillary expansion
Rapid palatal expansion
RME
Orthopedics

description: Introduction
description: Maxillary constriction is a common condition, often resulting in maxillary crowding, blocked out teeth, functional shifts, asymmetric jaw growth and posterior crossbites. The standard of orthodontic care is treatment with a rapid maxillary expander (RME) with the goal of separating the midpalatal suture. Few studies have attempted to measure the forces applied by RMEs during treatment. The objective of this study is to pilot a novel method for measuring these forces.
description: Materials and Methods
description: Twenty-nine patients from 7 to 16 years of age undergoing rapid maxillary expansion with 2 or 4-banded Hyrax-style RMEs were recruited. Each expander underwent pre-clinical calibration before patient delivery. Patients returned daily for 2 jackscrew turns per day over a period of 11-15 days. The force of each turn was recorded. Photos were captured and diastema width was measured at each visit. Intraoral scans were captured at each visit, and maxillary occlusal radiographs were taken after the final day of turning. The forces of maxillary resistance to expansion were then estimated using turn force data and the expander-specific calibration curves.
description: Results
description: Our data corroborate previous findings that expansion forces range from 0 to 20 pounds (~10,000 g), with no decrease in force levels following sutural separation. Older patients (&gt;12.5 y.o.) exhibited higher overall expansion loads compared with younger patients (&lt;12.5 y.o.), but this difference did not become significant until later treatment. Rate of load accumulation (slope) decreased after sutural separation in all patients. Slope decrease was statistically significant for the overall group (60% decrease), younger group (70% decrease), and older group (50% decrease). The magnitude of slope change was not significantly different between groups, and was extremely similar for all groups, regardless of age (all groups decreased approximately 280 g/day). A midline diastema appeared after an average of 11.5 activations and was not affected significantly by band number or age group. There was no significant difference in size of diastema between 2-banded and 4-banded RMEs, and diastema size was approximately 35% of total expansion on average.
description: Conclusions
description: Older patients showed higher overall expansion forces than younger patients, and the difference became statistically significant in the later part of treatment (after 22 activations, and at load maximum). Predicted load did not decrease significantly after midpalatal suture separation for any group, suggesting that the midpalatal suture is not the only source of skeletal resistance to expansion. However, rate of load accumulation (slope) decreased dramatically for all groups (50-70%) after separation of the suture, suggesting that it does make a significant contribution to total skeletal resistance. The magnitude of slope decrease was not different between age groups, which suggests that midpalatal suture resistance may not increase significantly with age. Maturation of the bony articulations of the maxilla with other components of the maxillofacial complex (zygomaticomaxillary sutures, pterygomaxillary sutures) may be primarily responsible for the observed increases in expansion force and RME failure rates with increasing age.