Study On Inclination And Height Of Molars And Incisors In Skeletal Class ? Malocclusion

ObjectiveTo investigate the development trend of first molar and incisors and their correlation with measuring plane in untreated skeletal class ? division 1 malocclusion and provide guidance for clinical treatment.MethodsThe sample was consisted of 213 untreated patients with skeletal class ? malocclusion and 92 skeletal class I malocclusion. The patients were divided into different groups according to their gender and cervical vertebral maturation stages.Measurements of the first molars and incisors items were done on lateral cephalograms with Dolphin 11.7.ANOVA was used to compare the difference between different groups.Results1. 3 * 2 factorial analysis results showed that the items were statistically significant interaction between bone age and sex factors were L1-MP(°) and L6-MP(mm). The main effect of bone age were significant for five items- U6-SN(°), U1-PP(mm), L1-MP(mm), U6-PP(mm) and L6-MP(mm). The main effect of skeletal type factors were significance for four items- L1-MP(°), U6-SN(°), U1-PP(mm), L1-MP(mm). The main effect of gender factors were significant for five items-U6-SN(°), U1-PP(mm), L1-MP(mm), U6-PP(mm) and L6-MP(mm).2. In male and female groups, the height and inclination of maxillary molars, height of mandibular molars and height of mandibular incisors in Mature groups were higher than those in Growing groups, and all of the differences were statistically significant.3. The differences of the inclination of maxillary and mandibular incisors between skeletal Class I and Class ? group were statistically significant. In addition to the Growing of male group, the inclination of maxillary molars in skeletal Class ? group less than skeletal Class I group, and the differences were significant difference. The differences of the height of mandibular incisors in Mature groups between skeletal class I and ? group were significant.4. At the Growing of the skeletal Class ? groups, the mandibular plane angle showed negative correlation with the inclination of maxillary and mandibular molars, inclination of mandibular incisors, and positive correlation with the occlusal plane angle, height of maxillary and mandibular incisors(female groups). In Mature and skeletal Class ? group, the mandibular plane angle showed negative correlation with the inclination of mandibular incisors, inclination of maxillary and mandibular molars(female groups), and positive correlation with the occlusal plane angle, height of maxillary incisors, height of mandibular incisors(female groups).Conclusions1. The inclination and height of molars and incisors are changes with the growth.2. With the difference of the mandibular plane angle, the teeth will show the corresponding compensation.3. Orthodontic treatment should make full use of the compensation of the dentition in order to achieve a good effect and stability.