Effect Of Physiologic Anchorage Spee-wire System On Maxillary First Molar With Different Alveolar Bone Height

Objective:To study the effects of physiological anchorage control technique（Physiologic Anchorage Spee-wire System,PASS）and Mc Laughlin-Bennett-Trevisi(MBT^TM)straight wire appliance on right side maxillary first molar with different alveolar bone height during the period of simulated sliding closing the extraction space,so as to provide the theoretical basis of biomechanics for oral clinical treatment.Methods:The CT scanning data of the jaw of the volunteer were input into Mimics20.0 software.The three-dimensional finite element models of the maxillary first molar,periodontal ligament,alveolar bone and buccal tube were obtained by using Autodesk3ds Max 2020,CATIA V5R20,ANSYS Workbench 19.2 and other modeling software.The PASS and MBT groups of the maxillary first molar with alveolar bone absorption of 0mm,2mm and 4mm were established,and 30 working conditions were obtained by applying 60g,80g,100g,150g and 200g forces in mesial direction.The movement of the maxillary first molar was simulated during the extraction space was closed,and the displacement trend and stress distribution of periodontal ligament and alveolar bone were analyzed.Results:Under the same force and the same alveolar bone height,the maximum initial total displacement of the maxillary first molar in PASS groups was smaller than that in MBT groups.And the trend of mesial lingual torsion and buccal inclination,mesial tilt movement and maximum initial equivalent stress of periodontal ligament in PASS groups with alveolar bone resorption were smaller than those in MBT groups.In addition,the stress of periodontal ligament increased with the increase of alveolar bone resorption and adduction force.Conclusion:For the orthodontic treatment of chronic periodontitis patients in the stage of closing the extraction space,the physiological Anchorage Spee’s arch system has the advantages of mesial-distal anchorage control and vertical control over the MBT straight wire system,and is more beneficial to the periodontal health of patients,and take care of the control of torque and torsion.