A 3-D Finite Element Study Of Whole Maxillary Dentition Distalization By Using Mini-implant With Customized Lingual Appliance

ObjectiveTo establish 3-D finite element models included customized lingual brackets, lingual arch wire, lever-arms, dentition, periodontal ligaments, alveolar bone and micro-implants. The aim was to analyze the mechanical characteristics during whole maxillary dentition distalization by using micro-implants with customized lingual appliance, which set a reference for clinic appliance. Methods3-D finite element models were established in section 1, the method is as following. 256-row computed tomography was applied to scan volunteer’s maxillary. Mimics, Geomagic Studio and ANSYS were employed to develop 2 volume models, then 3-D finite element models were established after dividing FEM mesh. The first 3-D finite element model(micro-implants were located at 6mm from the alveolar ridge crest of the palatal side between second premolar and first molar, lever-arms were located at the distal side of lateral incisor)includes 1332618 elements and 2049446 nodes. The other 3-D finite element model(micro-implants were located at 6mm from the alveolar ridge crest of the palatal side between the first and second molar, lever-arms were located at the distal side of canine) includes similar elements and nodes.The changing regularity of the dentition displacement was studied in section 2, 2.5N forces were given on the top of micro-implants through the lever-arms in the length of 3mm, 6mm and 9mm, the initial displacement of the dentition was observed and analyzed. The changing regularity of stress distribution on the periodontal ligaments was studied in section 3, work conditions were as the same as section 2, vonmises stress, major principal stress and minor principal stress were observed and analyzed. ResultsIn section 1, two 3-D finite element models including customized lingual brackets, lingual arch wire, lever-arms, dentition, periodontal ligaments, alveolar bone and micro-implants were successfully established. In section 2, as the length of the lever-arm increased from 3mm to 9mm, anterior teeth buccal to lingual inclination decreased, which is better for torque control,rotation near the lever-arms increased, which is considered as the adverse effect in horizontal plane during maxillary dentition distalization. In section 3, as the length of the lever-arm increased, vonmises stress, maximum tension stress and maximum compressive stress increased, the stress distribution in the periodontal ligaments mainly focused on the cervix of teeth near the lever-arms. Conclusions1. The 3-D finite element models of whole maxillary dentition distalization with customized lingual brackets from interdental micro-implants was built, which has not been report in the current journal. Their perfect biological fidelity and clinical similarity laid the foundation of further research.2. During the micro-implants aid whole maxillary dentition distalization with customized lingual system, the pattern of teeth movement could be controlled by changing the length of the lever-arm, it shall be not more than 6 mm while the micro-implant is located at 6mm from the alveolar ridge crest on the palatal side. During the treatment, lingual inclination and extrusion of the anterior teeth, expansion of the middle dental arch, rotation of teeth near the lever-arms should be take into account, as well as the periodontal status of the teeth near the lever-arms, especially in the alveolar ridge crest area.