Three-Dimensional Research Study Of Upper Incisor Position,Upper Anterior Alveolar Bone Morphology And Oropharyngeal Airway Volume Change After Treatment Of Class Ⅱ Bimaxillary Protrusion In Adult And Adolescent

Objective:This study is aim to compare the difference in the three-dimensional position of the upper incisors,upper anterior alveolar bone structure and oropharyngeal airway volume after treatment of Class Ⅱ bimaxillary protrusion in adult and adolescent.To predict the way of teeth move,alveolar bone morphology,change trend and oropharyngeal airway volume change of the people in different growth stages.To give a reference of moving teeth in a safe region when treat Class Ⅱ bimaxillary protrusion of different growth stages people,what’s more,to make sure the impact to the oropharyngeal airway.Method:Experiment 1:32 cases of Class Ⅱ bimaxillary protrusion were selected to this study.Group A is the adult group,Group B is adolescent.There are 16 cases in each group(A:3 male,13 female,25±2.3 mean age;B:7 male,9 female,12±2.8 mean age).The cases are all have CBCT scans before and after treatment.We use Cartesian coordinates to measure the three-dimensional position of the upper incisors before and after treatment.Finally,we use Spass 23.0 to compare the difference between two groups by using t test and other correlation analysis.Experiment 2:We choose same cases of experiment 1.They are all diagnosed Class Ⅱbi-maxillary protrusion and treated with extraction of four premolars.They are divided into 2 groups.Group A is adult(3 male,13 female),Group B is adolescent(7 male,9 female).The two groups all have CBCT scans before and after treatment.We choose the mid-sagittal slice of the incisors under MPV and then measure the apical level,mid-root level and 13.6mm away from the incisor point along the long axis for the thickness of alveolar bone and the crest height before and after the treatment.Finally,we use Spass 23.0 to compare the difference of the data by using t test and other correlation analysis.Experiment 3:The cases are the same of the experiment 2.The pre-(T1)and post-treatment(T2)Cone Beam Computed Tomography scans were oriented using the cranial nerve canals to set the 3 planes of reference.We use the Sinus/Airway measurement of Dolphin 11.5 to measure the upper airway volume,surface square,and Area of maximum pharyngeal constriction before and after treatment.At the same time,we measure the upper arch perimeter before and after treatment.Finally,we use Spss 23.0 to compare the difference of the data by using t test and other correlation analysis.Result1:The three-dimensional measurement disclose that the crown and root tip of the two group are retracted:11 apex 3.75±2.4mm(P≤0.05)、0.03±2.7mm,21 apex 3.14±3.01mm(P≤0.05)、-.18±2.92mm;11 crown 11 为 7.6±4.38mm(P≤0.05)、3.4±2.46mm(P≤0.05),21 crown 6.79±4.22(P≤0.05)、3.21±3.25mm(P≤0.05);in the sagittal plane.It means that the crown moved more distally than the root tip;and in the axil plane,11 apex-.71±6.73mm、-.68±4.85mm,21 apex 1.04±5.45mm(P≤0.05)、-.45±4.34mm;11 crown 1.2±5.48mm,-.4±4.26mm,21 crown 2.7±6.9mm、-.4±4.38mm;It is saying that we intruded the crown more than the root tip;however,they moved few horizontally.As the comparison of the two groups,both in the sagittal and axil plane,it has no significance difference between groups.2:After treatment,the labial thickness all showed a few increase in the adult group.A1、A2 of 11 and A2 of 21 have significant difference(p≤0.05).In the palatal bone,all bone thickness suffered significant decreasement except for P1 of 21.As for the alveolar height,the palatal height suffered significant decreasement(p≤0.05),and the labial height also decreased.In the adolescent group,the trend of the change are same to the adult group.3:At T1,the arch perimeter of the groups are all decresed.It shows that the arch perimeter reduced significantly after treatment in both groups.But,it has no differenct between groups.As to the upper airway,the airway volumes,airway surfaces and MinAx showed an increasement in the adolescent group at T1,but it do not have significant difference between groups.In the adult group,all of the measurement enjoyed an increasement,but no significant difference.What’s more,the arch perimeter change has low correlation with airway change.Conclusions:After treatment of the Class Ⅱ bi-maxillary protrusion patients in adult and adolescent,the upper incisors moves upward and backward significantly,and the vertical dimension weill.The profile improves.However,the maxilla of the adolescent showed a anteriorly growth.Meanwhile,the alveolar bone thickness are thicker in the adolescent group before treatment,but,the ability of modification in two groups showed no significant difference.The bone thickness all suffered a reduction and the crest height reduced,especially in the lingual side.After treatment,the Oropharyngeal Airway of the adult group do not show a significant change,the arch perimeter reduced significantly.However,in the adolescent group,the airway volume、airway surface and MinAx showed a significant inreasement.According what said above,when we make treatment plan the treat these patients of the kind,we should pay more attention to the bone thickness and avoid retract the teeth beyond the physiological limitation.As to the airway,the treatment will not improve the volume.