The Study Using CBCT On The Orthodontic Tooth Movement Of The Maxillary Posterior Teeth Embedded To The Maxillary Sinus Floor

Objectives:To analyze the movement of the Maxillary posterior orthodontic teeth embedded to the maxillary sinus floor by the combination of Invivo Dental and CBCT.To explore the movement of the maxillary posterior orthodontic teeth embedded to the Maxillary Sinus floor under the action of orthodontic force,the reconstruction of maxillary sinus bone cortex and the root absorption after teeth movement.To guide orthodontic doctors design orthodontic treatment in the patients and provide theoretical reference for the diagnosis of clinical doctors.Methods:A retrospective analysis of CBCT imaging data of patients who were treated in the Department of Orthodontics,the Attached Qujing Hospital of Kunming Medical University during 2014.01-2019.12 was performed.By collecting 18 orthodontic patients(including 5males and 13 females,age from 10 to 22,mean age,16.05years)who meet the inclusion criteria,CBCT data of patients before and after orthodontics treatment were converted into DICOM format into Invivo Dental measurement software to establish a three-dimensional coordinate system through bony marker points.The distance of roots movements of maxillary target teeth and the angle change of virtual tooth axis projected on the Mid-sagittal plane were measured.After orthodontic treatment,tooth movement,root absorption and reconstruction of maxillary sinus floor were evaluated.Data were processed by SPSS 22.0 software package.Results:1.The relationship between maxillary experimental tooth roots and the floor of maxillary sinus:the contact ratio of the mesiobuccal root,distobuccal root and palatine root to the floor is 86.11%,88.89%and 94.44%.In the classification of root and the floor of maxillary sinus,75%of palatine roots of maxillary first molar and 19.44%of buccal roots of maxillary second premolar entering maxillary sinus.Furthermore,16.67%of the mesiobuccal root,11.11%of the distobuccal root and 38.89%of the palatine root showed classification four.2.There was no significant difference in the distance between nasion and Frankfort Horizontal Plane before and after orthodontic treatment(P>0.05).3.There was significant difference in the distance between each root tips and Frontal plane before and after orthodontic treatment.The distance between the molar middle of the mesio-marginal ridges(or the maxillary second premolar cusps)and the Frontal plane was significant before and after orthodontics(P<0.05).Indicting that the root tips and crown points of maxillary first molar and maxillary second premolar all developed mesial movement.4.The angle between each root tip and each cusp projected on the Mid-sagittal plane and the Frontal plane was significant differences before and after orthodontic treatment(P<0.05).And the angle was obviously increased,indicting that the tooth movement was inclined.5.There was no significant difference in tooth length before and after orthodontics(P>0.05).Indicting that the target teeth show mainly mild absorption,and no severe absorption and extreme absorption.Conclusions:1.Among the maxillary first molar three roots,the relationship between the palatine root and the the floor of maxillary sinus is the closest,and the probability of the palatine root penetrating into the superior maxillary sinus cavity is the highest.2.The Maxillary posterior teeth embedded to the Maxillary Sinus floor can move during orthodontic treatment,and the tooth movement was inclined.3.The Maxillary Sinus floor which is closely related to the maxillary posterior teeth can reconstructed during orthodontic treatment.