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Boosalis Toaddy Thesis-Template-2025-26-PC_13.53 MB
Embargoed Access, Embargo ends: 06/29/2027
Thesis
Etiology of mandibular anterior arch collapse and mesial molar drift: a finite element analysis study
University of Iowa
Master of Science (MS), University of Iowa
Spring 2026
DOI: 10.25820/etd.008536
Abstract
INTRODUCTION
Relapse of aligned mandibular anterior teeth and the progressive collapse of the anterior mandibular arch is a significant problem for orthodontists. The etiology of this collapse is unknown, as is the cause of mesial molar drift. The purpose of this study was to investigate the influence of tongue pressure, lip-cheek pressure, and interdental force on these phenomena.
METHODS
Three-dimensional finite element models of the mandible were created, and the mandibular dentition was subjected to a wide range of tongue pressures, lip-cheek pressures, and interdental forces. Measurements of the effects of these loads on teeth displacements were made. Subsequently, the mandibular dentition was subjected to simultaneous application of literature-described mean values for tongue pressure, lip-cheek pressure, and interdental force. Displacement measurements were repeated.
RESULTS
Tongue pressure resulted in generalized arch expansion and spacing. Lip-cheek pressure and interdental force resulted in generalized arch collapse, anterior crowding, and mesial molar displacement. Simultaneous application of mean values for all three loads resulted in incisor crowding, a reduction of inter-canine width, and mesial molar displacement.
CONCLUSIONS
The simultaneous simulated application of three quasi-continuous intra-oral loads, tongue pressure, lip-cheek pressure, and interdental force results in incisor crowding, a reduction of mandibular inter-canine width, mesial molar displacement, and reveals the potential underlying etiology of mandibular anterior arch collapse and mesial molar drift.
KEYWORDS
Finite element analysis, equilibrium theory, orthodontic relapse, mandibular anterior arch collapse, incisor crowding, mesial molar drift
Details
- Title: Subtitle
- Etiology of mandibular anterior arch collapse and mesial molar drift: a finite element analysis study
- Creators
- Elaine C. Boosalis Toaddy
- Contributors
- Steven Marshall (Advisor)Emma Mueldener (Committee Member)Nicole Kallemeyn (Committee Member)Kyungsup Shin (Committee Member)Lina Moreno Uribe (Committee Member)Thomas Southard (Advisor)
- Resource Type
- Thesis
- Degree Awarded
- Master of Science (MS), University of Iowa
- Degree in
- Orthodontics
- Date degree season
- Spring 2026
- DOI
- 10.25820/etd.008536
- Publisher
- University of Iowa
- Number of pages
- xi, 77 pages
- Copyright
- Copyright 2025 Elaine C. Boosalis Toaddy
- Language
- English
- Date submitted
- 02/16/2026
- Description illustrations
- Illustrations, graphs, charts, tables
- Description bibliographic
- Includes bibliographical references (pages 71-74).
- Public Abstract (ETD)
The relapse of the mandibular anterior dentition is a continual frustration in the practice of orthodontics. Post-treatment many patients will experience relapse of the anterior dentition and crowding even after successful orthodontic treatment. The etiology of this phenomenon, along with mesial molar drift is poorly understood by clinicians and researchers alike.
The present study investigated light continuous forces applied daily inside and outside of the mouth, more specifically, tongue pressure, lip-cheek pressure, and interdental force and their contributions to the changes in dental position post-treatment. In using three-dimensional finite element modeling of the mandibular teeth these forces were simulated individually and simultaneously to measure their effects, respectively.
Applied singularly, tongue pressure resulted in outward dental expansion and spacing between the teeth, while lip-cheek and interdental forces resulted in inward dental collapse, mandibular incisor crowding, and mesial drift of the molar teeth. Applied simultaneously, these forces demonstrated inward collapse of the dental arch, incisor crowding, and mesial displacement of the molars.
The findings from the present study suggest that the equilibrium between these three forces contribute to post-treatment orthodontic relapse, and progressive mandibular incisor crowding. An understanding of these simultaneous and continuous forces aid in our understanding of mandibular crowding and mesial molar drift providing information to guide strategic retention protocols to improve long-term orthodontic stability.
- Academic Unit
- Orthodontics
- Record Identifier
- 9985176873002771
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