Cephalometric Characteristics Of Class ? Division 2 Malocclusion Among Different Skeletal Pattern

Objective Subdivide Class II Division 2 Malocclusion on the basis of inclination of mandibular ramus and mandible,in order to investigate cephalometric characteristics of Class II Division 2 malocclusion among different skeletal patterns.Thus to explore the mechanism of Class II Division 2 malocclusion,provide guidance for differentiate diagnosis and treatment strategy.Methods 127 adult Class II2 patients referred for the Affiliated Stomatology Hospital of Z hejiang Chinese M edicine U niversity,Hangzhou P erfect Dental Hospital or Hangzhou Stomatological Hospital were recruited,and lateral cephalograms of these patients were analyzed using Dolphin software.The coordinate system was established based on Frankfort plane(FH)a nd its perpendicular plane(VFH),then subtypes of Class II2 was identified on the basis of inclination of mandibular ramus and mandible determined by FMA a ngle(intersection a ngle of D owns mandibular plane a nd Frankfort pl ane)and A r Go'-VFH angle(intersection a ngle of Articular mandibular ramus plane a nd VFH plane).According to FMA(°)<22°,22 °~28°and >28°,t he patients were divided into A1,A2 and A3;According to Ar Go'-VFH angle(°)<-1°?-1°~4°?>4°,the patients were divided into B1,B2,B3.Thus all the subjects can be divided into A1B1(n=7),A1B2(n=12),A1B3(n=15),A2B1(n=19),A2B2(n=16),A2B3(n= 8),A3B1(n= 25),A3B2(n= 15)a nd A3B3(n= 10).C ephalometric measurements i nclude m orphology of base a nd j aws,r elationship of maxilla a nd mandible,d ento-alveolar h eight,morphology of m andibular s ymphysis,f eatures of upper incisors and soft tissues.All the statistical analysis were performed by SPSS 22.0 using two-way FANOVA(3 × 3),SNK(Student-Newman-Keuls)were applied if there was a statistically significant difference(p?0.05).Results No interaction effect was found between A and B(P>0.05);SNK analysis between subgroups shows:A1 was larger compared with A3 in SNB(°)?B-Go'/S-N(%)?B-Ar/S-N(%)?Ar-S/S-N(%)?S-Go'/N-Me(%)?B-Pog/MP(°)?B-Pog(mm)?LL'-B'-Pos(°),smaller in ANB(°)?A-PTM/ B-Go'(%)? A-PTM/ B-Ar(%)?MP-OP(°)?PP-MP(°)?OP-PP(°)?ANS-Me/Ar-Go'(%)?MP-SN(°),UI-PP(mm)?LI-MP(mm)?U6-PP/Ar-Go'(%)?L6-MP/Ar-Go'(%)?OP-FH(°);While B1 was small compared with B3 i n S NB(°)? A-B(mm)? B-Ar/S-N(%)? A-PTM/ B-Go'(%)? PTM-S/SN(%),U1/SN(°)?U1/PP(°),ANB(°)?A-PTM/ B-Ar(%)?MP-OP(°),larger in OP-PP(°)?PP-FH(°),UI-PP(mm)?UI-ANS/ANS-Me(%)?L6-MP/Ar-Go'(%)Conclusion We recommended a subdivision of Class II Division 2 malocclusion on the basis of inclination of mandibular ramus and mandible,and conclude that there was a morphology difference between different s keletal patterns o f C lass I I Division 2 Malocclusion.Compared with low angle p atients,high angle pa tients m ight ha ve shorter sagittal length of the mandible.They might have larger anterior dento-alveolar height,but smaller of that in low angle patients.Even though there was no difference in posterior dento-alveolar height between high angle and low angle patients,the latter might show i nsufficient pos terior dento-alveolar h eight relative to p osterior f acial height.The inclination of mandibular ramus might be related to the degree of overbite and r etroclination of incisors.The patient with less inclination of mandibular ramus might have steeper p alatal plane,larger u pper a nterior dento-alveolar he ight,more retrocline of upper incisors as well was severer overbite,but normal size of mandible body.This dental deformity might restrict forward growth of mandibular ramus and lower arch,therefore a growing mandible that is unable to carry its dentition forward would thus develop a more defined chin.It is suggested to intrude incisors in high angle patients,sometimes properly intrude lower molars in order to improve profile.It is proposed to properly extrude lower molars to correct overbite in low angle patients.The patient with less inclination of mandibular ramus might have severer retroclined overbite,so the incisors should be properly intruded and proclined.The retention strategy should consider the maintenance of the changing dento-alveolar height as well as the inclination of incisors.