Glenoid Fossa And Condylar Process Position In Different Age Group In Class â…¡ Malocclusion

Background and purpose:ClassⅡmalocclusion is one of most popular kinds of malocclusion, and it is not only high disease rate, but also bad facial esthetics and severe malfunction. ClassⅡskeletal malocclusion maybe show maxillary excess,mandibular deficiency or both of them, among which mandibular deficiency is most popular kind. It is a nodus in orthodontic treatment. At present, the therapies contain early therapy, camouflage orthodontic treatment and orthodontic - orthognathic combination therapy. Early therapy means orthopedic treatment during growth, but the treatment effect is controversial. Some studies confirm functional appliance can lead stomatognathic system to normal growth and development. But the other results show that functional appliances can do little things. Because functional appliance can promote or restrain jaws only on the basis of normal growth, the treatment must take it into consideration. Researchers have proved that there are close relationships between glenoid fossa and condylar process position and morphology with malocclusion. So, this study analyse the position changes of glenoid fossa and condylar process in children and adults in ClassⅡmalocclusion, aiming to give some advise to early treatment.Method:A cephalometric study was carried out on a sample of 171 subjects, who were selected from the patients of department of orthodontics in Zhejiang University School of Medicine Affiliated Stomatological Hospital. Criteria for case selection include:1) facial symmetry and normal angle vertical relationships; 2)no orthodontic treatment, injury, TMJ trauma, and surgical treatment history; 3)lateral films with well detectable contours of the glenoid fossa; 4) vertical relation:mixed dentition-- normal facial skelete:32.2°39.4°; Permanent teeth period－－normal facial skelete: 27.3°37.7°5) ClassⅡskeletal malocclusion,mixed dentition ANB> 6.1°,Permanent teeth period ANB> 4.7°.These subjects were divided into two groups: children group (7-12 years old,95 subjects with 32 ClassⅠmalocclusion.30 ClassⅡmalocclusion,33 ClassⅢmalocclusion) and adult group (18-25 years old,76 subjects with 27 ClassⅠmalocclusion,25 ClassⅡmalocclusion,24 ClassⅢmalocclusion). Each groups were homogenous as to age and sex distribution. All cephalograms were taken by means of the same X-ray device and by a single technician and then were measured by myself. All of the data was analysed by SPSS 16.0. The data in each group was compared by Kruskal-Wallis H test. If there was statistical significance, the data will be compared by Mann-whitney U test further. Set P<0.05.Result:In children group, the comparisons among malocclusions according to the sagittal relationships revealed significantly larger distances T-Fs',T-Ar' ANS-SBL,PNS-SBL,Me-SBL and Go-SBLin skeletal ClassⅡwhen compared with skeletal ClassⅢ. But when compared with skeletal ClassⅠ, only distances ANS-SBL and PNS-SBL were significantly larger. Distance T-Fs'in skeletal ClassⅢmalocclusion was significantly smaller than in ClassⅠ, while T-Fs'was similar. In adult group, although distances T-Fs'and T-Ar'didn't have any significant difference, PNS-SBL,Go-SBL,Ar-Go,Go-Pg distances in skeletal ClassⅡwere significantly smaller than skeletal ClassⅢ. When compared with skeletal ClassⅠ, Ar-Go,Go-Pg distances are significantly smaller in skeletal ClassⅡ, but significantly larger in skeletal ClassⅢ. Conclusion:This study indicates that glenoid fossa and condylar process positions contribute to different craniofacial patterns in chilfhood. With the growth and development, jaws especially mandible play an important role in the establishment of different craniofacial patterns, but glenoid fossa and condylar process didn't have any change. In skeletal ClassⅡ, the growth of mandible is Development limited.This study would provide some references for the orthodontical diagnosis,treatment and craniofacial growth and development.