Abstract
BackgroundTorque of the maxillary incisors is crucial to occlusal relationship and esthetics and can be influenced by many factors. The aim of this study was to assess the relative influence of the material of the orthodontic appliance (adhesive, bracket, ligature, and wire) on tooth displacements and developed stresses/strains after torque application.MethodsA three-dimensional upper right central incisor with its periodontal ligament (PDL) and alveolus was modeled. A 0.018-in. slot discovery® (Dentaurum, Ispringen, Germany) bracket with a rectangular 0.018 x 0.025-in. wire was generated. The orthodontic appliance varied in the material of its components: adhesive (composite resin or resin-modified glass ionomer cement), bracket (titanium, steel, or ceramic), wire (beta-titanium or steel), and ligature (elastomeric or steel). A total of 24 models were generated, and a palatal root torque of 5° was applied. Afterwards, crown and apex displacement, strains in the PDL, and stresses in the bracket were calculated and analyzed.ResultsThe labial crown displacement and the palatal root displacement of the tooth were mainly influenced by the material of the wire (up to 150% variation), followed by the material of the bracket (up to 19% variation). The magnitude of strains developed in the PDL was primarily influenced by the material of the wire (up to 127% variation), followed by the material of the bracket (up to 30% variation) and the ligature (up to 13% variation). Finally, stresses developed at the bracket were mainly influenced by the material of the wire (up to 118% variation) and the bracket (up to 59% variation).ConclusionsThe material properties of the orthodontic appliance and all its components should be considered during torque application. However, these in silico results need to be validated in vivo before they can be clinically extrapolated.
Highlights
Torque of the maxillary incisors is crucial to occlusal relationship and esthetics and can be influenced by many factors
The basis for orthodontic tooth movement is founded in the ability of the periodontal ligament (PDL) and surrounding bone to react to a mechanical stimulus and subsequent displacement of the tooth with remodeling processes [11, 12]
Complex biomechanical questions like those of orthodontic force application to teeth can be assessed with the finite element (FE) method, as has been done in several cases in order to assess the center of resistance of teeth [18,19,20], aspects of orthodontic efficiency [21, 22], different bracket [9, 23], anchorage [24, 25] or surgical [26] modalities, and retention procedures [27]
Summary
Torque of the maxillary incisors is crucial to occlusal relationship and esthetics and can be influenced by many factors. The aim of this study was to assess the relative influence of the material of the orthodontic appliance (adhesive, bracket, ligature, and wire) on tooth displacements and developed stresses/strains after torque application. The objective of the present in silico study was to assess the influence of the material characteristics of orthodontic appliances (adhesive, bracket, ligature, and wire) on the biomechanics of torque application. The set-up is similar to a previous study that investigated how differences in the tooth morphology, bracket prescription, and bracket positioning can affect tooth movement after torque application [28]
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