Three-dimensional finite element analysis of attachment design in the clear aligner treatment of extraction and upper anterior teeth retraction
Objective To evaluate biomechanical effect of different attachments on anchorage teeth during anterior teeth retraction with clear aligner by means of three-dimensional finite element analysis.Methods The study was conducted from May to August,2022 in the Orthodontics Department of Stomatology Hospital Affiliated to China Medical Universi-ty.Based on the CBCT data of an adult with maxillary protrusion,a clear aligner model was established by extracting maxillary first premolars.By means of three-dimensional finite element analysis,we analyzed the initial displacement of anchorage teeth(second premolar first molar and second molar)after a force of 2 N and the biggest Von-Mises stress of periodontal membrane,with no attachment group(NA)as the control group and mesial vertical rectangular attachments(VM),distal vertical rectangular attachments(VD),distal or mesial horizontal rectangular attachments(HM),distal hori-zontal rectangular attachments(HD)and grouped half-oval attachments(GO)assembled with the mod-el as 5 experimental groups.Results In the buc-cal and lingual direction,each group showed palatal displacement of the anchorage teeth crowns but roots had buccal movement trend.In the mesial-distal direction,second premolar and first molar,the axial tilt in the GO group,HD group,VD group,HM group,and VM group increased in turn.In the second molar,the HD group had the smallest axial tilt(12.322×10-4 mm),while the GO group had the largest tilt when compared with other experimental groups(18.311× 10-4 mm).Compared to all experimental groups,the NA group had a greater axial tilt.In the vertical direction,only the buccal apex of second premolar showed an elongation trend.The distal buccal apex of first molar crowns as well as mesial and distal buccal roots showed elongation trends.The crown and root of second molar showed an elongation trend.The maximum Von-Mises stress distribution of PDL was in the dental cervix in all groups.The maximal stress of the anchor-age teeth in the control group was greater than that in the corresponding experimental group.In all experimental groups,the maximal Von Mises stress on the periodontal membrane of second premolar was higher than the maximal stress that the periodontal membrane could withstand(0.026 MPa).Conclusion In the clear aligner treatment of extraction and upper anterior teeth retraction,the attachment can effectively reduce the tendency of mesial inclination movement of the anchorage teeth and Von Mises stress.The effect of the buccal distal horizontal rectangular attachment is better,which can improve the ability of three-dimensional control of the anchorage teeth.When removing and wearing appliances,be gentle and pay attention to protecting the periodontal tissue.
three-dimensional finite element analysisclear alignerattachment designorthodontic extractionanterior teeth retraction
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