Evaluating the Biomechanics of Tooth Movement induced through Orthodontic Braces using an Integrated Clinical and Mechanical Approach
Creators: Subramanian, Arya
Publisher: name: University of Alberta Library
Year: 2024

<p>Orthodontics is the dental specialization focused on correcting tooth and jaw misalignments. The treatment is known to have positive effects on the quality of life of the public by improving personal aesthetics and oral health. A common fixed treatment option is orthodontic braces, composed of orthodontic brackets bonded on the dental arch and an archwire inserted through the bracket slots. The interaction between the bracket slot and archwire complex causes orthodontic forces/moments to be applied onto the tooth, resulting in dental movement facilitated by alveolar bone remodelling. The relationship between the biomechanical forces and tooth movement occurring over treatment is poorly understood, limiting the predictability of orthodontic treatment and causing possible side effects such as unwanted tooth movements, longer treatment times, and tissue damage from high-magnitude forces. The limited understanding is largely attributed to insufficient research linking longitudinal clinical observations of tooth movement and biomechanical forces produced by braces.</p>

<pre><code>The objectives of this work were to first utilize clinical cases for obtaining bracket position information and measuring clinical tooth movement over orthodontic treatment by collecting digital intraoral scans and applying scan analysis techniques and in-house scripts. Secondly, the collected bracket positions were physically replicated onto an in vitro Orthodontic Simulator (OSIM) using custom-dimensioned jig sets with bonded brackets to measure the generated forces upon archwire insertion at each treatment interval. Lastly, existing trends were analyzed to better understand the relationship between the measured biomechanical forces produced by braces and the resulting clinical tooth movement magnitude, direction, and rate. 

The results of this thesis work showed that the developed methodology utilizing clinical scan analysis techniques and in vitro biomechanical experiments could be applied for a preliminary understanding of the longitudinal biomechanical force and tooth movement relationship. For the investigated clinical cases with mild anterior crowding, cases with larger misalignments generally experienced larger forces, tooth movements, and tooth movement rates between the initial intervals of treatment. For a particular archwire size, the initially measured forces were generally greater than the end forces indicating further tooth alignment as treatment progressed. It was also observed that force magnitudes generally increased for a particular treatment interval when a larger archwire was used. The observed trends between initial force and calculated tooth movement were both consistent and inconsistent. For directionally consistent trends, tooth movements and initial forces were measured in the same direction, while inconsistent cases involved initial force and tooth movement measurements in opposing directions. Other inconsistencies observed included force magnitudes lower than the observed tooth movement and vice versa. Inconsistent trends may have resulted from patient-specific characteristics such as tooth root morphology and periodontal tissue differences, and existing interactions between the dental arches or adjacent teeth, affecting the orthodontic force distribution and resulting tooth movements. The frequency of scan collection also limited the evaluation of the intermediate tooth movement sequence over treatment. 

The streamlined methodology presented in this thesis focused on the longitudinal tracking of biomechanical forces and clinical outcomes over orthodontic treatment. Potential applications of this work include investigating more complex tooth misalignments, developing patient-specific models for enhancing treatment predictability, and designing future orthodontic appliances for optimal load delivery.
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