Biomechanical Analysis Of Maxillary Posterior Tooth Intrusion By Clear Aligners

To analyze the stress concentration region and tooth displacement in maxillary posterior tooth intrusion by clear aligners. A finite element model of maxillary dentition, periodontal ligaments, and clear aligners was established. Six working conditions were set based on intruded teeth number, simulating single and simultaneous tooth intrusion. After applying an intrusion of 0.25mm, initial tooth displacements and stresses on periodontal ligaments were analyzed with ANSYS software. Three-dimensional finite element analysis of equivalent stress in the periodontal ligament revealed that stress concentrated primarily at the root apex and buccal cervical region of the anchor teeth during molar intrusion, while in premolar intrusion, stress was mainly localized to the intruded tooth. Molars and premolars showed effective single-tooth intrusion, with premolars performing better, but intrusion efficacy dropped in two teeth simultaneous intrusion. The intruded tooth exhibited buccal crown tipping (0.0186-0.0284mm) and lingual root tipping (0.00842-0.0273mm), while the primary anchor tooth showed lingual crown tipping (0.0103-0.0133mm) and buccal root tipping (0.00325-0.00547mm), and mesial crown tipping (0.0107-0.0140mm) of second molar was observed in first molar intrusion. Molar intrusion caused stress concentration at the anchor teeth’s root apex and buccal cervical zone, while premolar intrusion mainly produced stress on the intruded tooth, leading to possible root and labial alveolar bone resorption. Single-tooth intrusion was more effective than simultaneous tooth intrusion. Buccolingual and mesiodistal displacements of intruded and anchor tooth occurred, thus anchorage preparations are needed.