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Modeling the Midpalatal Suture during Maxillary Expansion Treatment and its Implication towards Appliance Design Open Access


Other title
maxillary expansion
Type of item
Degree grantor
University of Alberta
Author or creator
Romanyk, Daniel L
Supervisor and department
Carey, Jason (Mechanical Engineering)
Examining committee member and department
Major, Paul (Dentistry)
Carey, Jason (Mechanical Engineering)
Chen, Jie (Mechanical Engineering)
Toogood, Roger (Mechanical Engineering)
Dennison, Chris (Mechanical Engineering)
Department of Mechanical Engineering

Date accepted
Graduation date
Doctor of Philosophy
Degree level
Widening the maxilla, or upper jaw, is a common treatment in orthodontics used to generate additional room in the correction of tooth misalignments. Expansion is achieved through activation of an appliance inserted in the patients’ upper jaw. Currently, appliances utilizing expansion screws, spring, magnets, or shape memory alloys are being used by clinicians. The unfused midpalatal suture, soft connective tissue between maxillary bones, is also widened during this procedure. In the literature concerning this treatment and its impact on patient response, little has been done to consider the suture’s viscoelastic properties. Development of a viscoelastic model would allow for accurate prediction of suture response to the various expansion appliances and aid in guiding future appliance design and treatment protocols. In the presented thesis research, complete viscoelastic creep-relaxation models are developed for the unfused midpalatal suture. First, nonlinear creep-strain models are established based on experimental data from the rabbit midsagittal suture. Then, interrelation techniques are utilized to generate subsequent stress-relaxation relations based on the previously obtained creep-strain constants. Development of an overall creep-relaxation model allows for prediction of suture response to expansion appliances that exert a constant or decaying force (springs, magnets, shape memory alloys) as well as step-wise increases in displacement (expansion screws). In using developed creep-relaxation models to simulate the suture’s response to expansion appliances, several key observations were made. In regards to screw-activated appliances, it was found that stresses resulting from a single step-wise activation likely would not generate tissue failure; however, as few as two or three rapid activations may certainly do so. Additionally, stresses decayed rapidly to negligible values within minutes of screw activation. When considering appliances that exert a continuous force during expansion, it was determined that it is imperative to maintain as constant a force as possible; as the applied force decays over treatment, the amount of suture expansion generated closely follows this trend. Overall, it was found that an appliance able to generate a constant force throughout the entirety of treatment will be most effective in physiologically expanding the midpalatal suture. This in turn will decrease treatment time and improve overall results.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Romanyk DL, Lagravere MO, Toogood RW, Major PW, Carey JP. Review of maxillary expansion appliance activation methods: Engineering and clinical perspectives. Journal of Dental Biomechanics. 2010;2010:496906.Romanyk DL, Collins CR, Lagravere MO, Toogood RW, Major PW, Carey JP. Role of the midpalatal suture in FEA simulations of maxillary expansion treatment for adolescents: A review. International Orthodontics. 2013;11:119-138.Romanyk DL, Liu SS, Lipsett MG, Toogood RW, Lagravere MO, Major PW, Carey JP. Towards a viscoelastic model for the unfused midpalatal suture: Development and validation using the midsagittal suture in New Zealand white rabbits. Journal of Biomechanics. 2013;46:1618-1625.Romanyk DL, Liu SS, Lipsett MG, Lagravere MO, Toogood RW, Major PW, Carey JP. Incorporation of stress-dependency in the modeling of midpalatal suture behavior during maxillary expansion treatment. Proceedings of the ASME 2013 Summer Bioengineering Conference. 2013;2013:SBC2013-14034.Romanyk DL, Liu SS, Long R, Carey JP. Considerations for determining relaxation constants from creep modeling of nonlinear suture tissue. International Journal of Mechanical Sciences. 14-page manuscript submitted September 4, 2013

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