BACKGROUND:Based on the principle of vertical tooth movement,a personalized orthodontic appliance is created through digital design combined with 3D printing,so that the personalized orthodontic appliance forms a support system with the individual incisors.With the help of the absolute support of the micro-implant,the single tooth is precisely controlled in a three-dimensional direction.OBJECTIVE:To design personalized orthodontic appliances with 11,12,21,and 22 intrusion and extrusion based on biomechanical principles,and analyze the safety of the personalized orthodontic appliances in terms of their movement effect on the teeth by means of the three-dimensional finite element method.METHODS:Three-dimensional finite element models of alveolar bone-periodontium-maxillary incisors-personalized cantilever micro-implant-connecting plates-personalized brackets in the maxillary anterior region(teeth numbers 11,12,21,and 22)were established using Mimics,Geomagic Wrap,SolidWorks,and Ansys Workbench software,respectively.Personalized orthodontic appliances with low pressure movement and extended movement were set up at each tooth position.The stress level of each component of the personalized orthodontic appliances was analyzed,and the tooth displacement and periodontal stress distribution were calculated under loading of 300 g tensile or thrust force.RESULTS AND CONCLUSION:(1)The maximum equivalent force on the personalized intrusion mobile orthodontic appliance was 162.90 MPa,and the maximum equivalent force on the personalized extrusion mobile orthodontic appliance was 239.57 MPa.The maximum equivalent stress on both devices was located in the vertical portion of the personalized bracket loading attachment.The equivalent stresses on each part of the personalized orthodontic appliance were all within the yield strength,and they had good safety.(2)The initial displacement of the teeth under the action of the personalized orthodontic appliances showed a tendency towards overall intrusion or extrusion,with the displacement in the vertical direction far exceeding that in the horizontal and sagittal directions.The equivalent stress peak appeared at the root tip or neck of the periodontal membrane,and the equivalent stress concentration area appeared in the periodontal membrane of the root apical region.(3)The results show that the personalized orthodontic appliance allows 11,12,21,and 22 to approximate either intrusion movement or extrusion movement,initially confirming the effectiveness of the personalized vertical movement orthodontic appliance.

BACKGROUND:Based on the principle of vertical tooth movement,a personalized orthodontic appliance is created through digital design combined with 3D printing,so that the personalized orthodontic appliance forms a support system with the individual incisors.With the help of the absolute support of the micro-implant,the single tooth is precisely controlled in a three-dimensional direction.OBJECTIVE:To design personalized orthodontic appliances with 11,12,21,and 22 intrusion and extrusion based on biomechanical principles,and analyze the safety of the personalized orthodontic appliances in terms of their movement effect on the teeth by means of the three-dimensional finite element method.METHODS:Three-dimensional finite element models of alveolar bone-periodontium-maxillary incisors-personalized cantilever micro-implant-connecting plates-personalized brackets in the maxillary anterior region(teeth numbers 11,12,21,and 22)were established using Mimics,Geomagic Wrap,SolidWorks,and Ansys Workbench software,respectively.Personalized orthodontic appliances with low pressure movement and extended movement were set up at each tooth position.The stress level of each component of the personalized orthodontic appliances was analyzed,and the tooth displacement and periodontal stress distribution were calculated under loading of 300 g tensile or thrust force.RESULTS AND CONCLUSION:(1)The maximum equivalent force on the personalized intrusion mobile orthodontic appliance was 162.90 MPa,and the maximum equivalent force on the personalized extrusion mobile orthodontic appliance was 239.57 MPa.The maximum equivalent stress on both devices was located in the vertical portion of the personalized bracket loading attachment.The equivalent stresses on each part of the personalized orthodontic appliance were all within the yield strength,and they had good safety.(2)The initial displacement of the teeth under the action of the personalized orthodontic appliances showed a tendency towards overall intrusion or extrusion,with the displacement in the vertical direction far exceeding that in the horizontal and sagittal directions.The equivalent stress peak appeared at the root tip or neck of the periodontal membrane,and the equivalent stress concentration area appeared in the periodontal membrane of the root apical region.(3)The results show that the personalized orthodontic appliance allows 11,12,21,and 22 to approximate either intrusion movement or extrusion movement,initially confirming the effectiveness of the personalized vertical movement orthodontic appliance.