Three-dimensional finite element analysis of the en-masse retraction of lower anterior teeth in lingual bracket system / 中国组织工程研究

ABSTRACT

BACKGROUND: Lingual bracket system is the best invisible orthodontic appliance due to its aesthetics and efficiency, but it is difficult to control anterior tooth torque during the distal retraction of the anterior tooth. Thereafter, lots of studies on maxillary anterior teeth have been conducted, but there is less knowledge about the mechanical characteristics of whole mandible dentition distal retaction. OBJECTIVE: To analyze the biomechanical characteristics of the mandibular anterior teeth distal retracted by sliding method in lingual orthodontic treatment. METHODS: A three-dimensional finite element model was constructed using a series of specialized software based on volunteer's CT data and lingual brackets, including the mandible, alveolar bone, periodontal ligament, dentition (removal of the two first premolars), lingual brackets and arch wire with hooks (located between lateral incisor and canine and 11 mm distant from the arch wire plane). Subsequently, 1.5 N lingual forces through the hooks of first molar (2 mm distant from the arch wire plane) and the hooks between the lower lateral incisor and canine were loaded and the biomechanical characteristics of the mandibular anterior teeth movement during the en-masse retraction were analyzed. RESULTS AND CONCLUSION: The finite element model was constructed successfully, and had a higher geometrical similarity and resemblance of clinical situation. The crowns of lower incisors showed the tendency of lingual inclination and extension, and this tendency was more obvious in the lateral incisors. The canines were buccal and mesial inclination and intrusion. The periodontal stress concentration area was corresponded with the tendency of tooth movement. Therefore, the movement tendency of incisors is still lingual inclination when mandibular anterior teeth distal retracted by a longer hook in lingual brackets system, and there is no distal inclination. Overall, lower incisors are easy to exhibit lingual inclination; the long anterior hooks contribute to the movement of canines, but it is not available for the vertical control of incisors during mandibular anterior tooth distal retraction.