Study On Facial Profile Of Patients With Congenitally Missing 2 Mandibular Incisors And Changes Of Profile After Orthodontic Treatment By Extraction Of 2 Maxillary Premolars

Objective:To study the facial profile of the patients with congenitally missing 2 mandibular incisors,and to investigate the changes after orthodontic treatment by extraction of 2 maxillary premolars,by retrospective analysis of the lateral cephalometric radiographs of these patients.Methods:Lateral cephalometric radiographs before and after orthodontic treatment of 64 patients with congenitally missing 2 mandibular incisors were collected from the completed case library of Department of Orthodontics of the Stomatology Hospital of Jilin University,according to the inclusion criteria and exclusion criteria.The initial cephalometrics of 64 patients were used to characterize the facial profile.38 out of the 64 patients had undergone orthodontic treatment by extraction of 2 maxillary premolars,and the initial and final cephalometrics of which were used to compare the profile changes before and after orthodontic treatment.The cephalometries(including 20 hard and 10 soft tissue items)were performed using Dolphin Imaging software.The initial cephalometries of 64 patients were compared with Chinese standards using one sample t test,and paired sample t test was used to compare the results of cephalometrics before and after treatment by extraction of 2 maxillary premolars.Results:Compared with Chinese standards,patients with congenitally missing 2 mandibular incisors had larger overjet,overbite,ANB,U1-NA angle,face angle,Y axis,Pg-NB,face convexity,soft tissue facial angle,H angle,mentolabial sulcus to H-Line(P<0.05);smaller SNA,SNB,L1-NB angle,Ll-NB distance,L1-MP,occlusal plane angle,mentolabial sulcus angle,upper lip protrusion,lower lip protrusion(P<0.05);but had no significant difference regarding U1-NA distance,U1-SN,MP-FH,U1-L1,NA-APg,ANS-Me/N-Me,S-Go/N-Me,nasolabial angle,subnasale to H-Line,soft tissue upper/lower face height ratio(P>0.05).After orthodontic treatment by extraction of 2 maxillary premolars,the patients showed smaller overjet,overbite,U1-NA angle,U1-NA distance,U1-SN,H angle,upper lip protrusion,subnasale to H-Line(P<0.05);larger L1-NB angle,L1-NB distance,L1-MP,occlusal plane angle,Pg-NB,ANS-Me/N-Me,mentolabial sulcus angle(P<0.05);but no significant difference regarding SNA,SNB,ANB,MP-FH,U1-L1,face angle,NA-APg,Y axis,S-Go/N-Me,face convexity,nasolabial angle,soft tissue face angle,lower lip protrusion,mentolabial sulcus to H-Line,soft tissue upper/lower face height ratio(P>0.05).Conclusion:Patients with congenitally missing 2 mandibular incisors had insufficient mandibular development but adequate development of the chin,larger overjet and overbite,lingually inclined lower incisors,deeper and sharper mentolabial sulcus.After orthodontic treatment by extraction of 2 maxillary premolars,the overall appearance of the lateral profile remained unchanged,but the occlusion of anterior teeth was significantly improved.