Biomechanical Research Of Invisible Appliance Techniques

Background: Since 1999 when invisalign was used in clinical application, invisalign has been popular with both orthodontists and patients for its advantages, such as being transparent, invisible, comfortable, moveable, sanitary and predictable. Recently, some institutes and a technology corporation co-operated and developed the invisible orthodontic treatment system. Their products have been applied clinically. The technology of invisible appliances is the application of computer technology in orthodontics, which is definitely different from the traditional fixed aligners. It is most important to master the force and its way of action in orthodontics. Because orthodontists can't master accurately orthodontics forces of invisible appliances at present, invisible appliances are limited seriously to develop and spread. Up to now, there are many introductions and applications to invisible appliances, but few biomechanical researches under orthodontics forces with invisible appliances techniques. Therefore, it will be important and innovative to study biomechanics under orthodontics forces with invisible appliances techniques.Objectives: To provide directions to the design and application of invisible appliances, orthodontics forces system and biomechanics effect under orthodontics forces with invisible appliances techniques are studied. The orthodontics forces under invisible appliances are distributed, which is much different from that of traditional fixed aligners. The moving tendency of teeth can be predicted by researching and analyzing the magnitudes and distributions of teeth and tissues around teeth, which can help orthodontists estimate whether the result is right or not. Aiming at one kind of tooth's monstrosity, several simulated cases applied with invisible appliances are designed and analyzed, which are compared with that of traditional fixed aligners to select the most proper one and direct design and clinical application of invisible appliances.Methods: A three-dimensional FE model of canine with the invisible appliance was set up, which includes alveolar bone, periodontal membrane and pulp. Aiming at one kind of tooth's monstrosity, several simulated cases are designed and analyzed numerically. The force and stress distributions applied with the invisible appliance were obtained. And the comparative study was made between the invisible appliance and the traditional fixed aligner. With the method of rapid forming from CT, more accurate models of mandible, all teeth including tissues around them and a set of invisible appliances are set up and assembled according to the actual condition of patient. These assembled models are imported into the software of FE and meshed. To finish the biomechanical research applying with invisible appliance, contacting analysis method is used in the software of FE.Results: The maximal stresses around the maxillary canine are greatly close, and changing tendency of stresses is very similar, while applied with the invisible appliance and the traditional fixed aligner. With the method of rapid forming from CT, more accurate models of mandible, all teeth including tissues around them and a set of invisible appliances are set up. According to the actual conditions of patients, assembly of these models is completed. By contacting analysis method in the software of FE, biomechanical research of invisible appliance technique is finished.Conclusions: Orthodontic forces system and its biomechanical effect under orthodontics forces with invisible appliances techniques are studied, which can be used to direct design and clinical application of invisible appliances.