Cephlometric Analysis Of Class Ⅱ～1 Malocclusion With Different Vertical Type In Adolescences

Class II1 malocclusion plays an important role in orthodontics. Initially, in the diagnosis and treatment planning of Class II1 malocclusions, special attention was placed on the anteroposterior relationship as indicated by the Angle classification of malocclusion. The role of vertical dimension finally was recognized later because of the contributions of many orthodontists. And class II1 malocclusion was classified into several vertical types. However few comparative researches between different vertical types have been done.The purpose of this study was to analyze cranioficiodental vertical discrepancies of class II1 with different vertical type in adolescences and to learn how to control the vertical dimensions. 120 subjects including 60 males and 60 females aged from 12-14 years were selected. All the subjects had not received orthodontic treatment. They were divided into four groups by madibular plan. Three groups with different vertical type Class II1 malocclusion. high-angle, low-angle and average angle, and one group with normal occlusion. Every group has 30 cases. All cephalograms of four groups weretraced by the author. Data were obtained to have analysis of variance and LSD test.Comparing the every group of class II1 with normal occlusion group. The results indicated that:1) The cranial floor base angle of three groups with class II1 malocclusion increased. The anterior cranial floor angle was more open in the high-angle group, and the flexure of the middle cranial floor increased in the low- angle and average angle group. The effective vertical growth of cranial floor decreased while the mandibular plan angle increased.2) The vertical growth of the anterior maxilla of the three groups with class II1 malocclusion was decreased excessively relative to the posterior maxilla. The vertical growth of the composite ramus-cranial floor was deficient relative to the anterior maxilla in the high-angle and average angle group, the mandible rotated backward wholly, especially in the high-angle groups, and the gonial angle increased. In the low-angle group, the vertical dimension of the composite ramus-cranial floor was long excessively relative to the posterior maxilla, the palatal plane and mandible plane rotated forward and upward, and the gonial angle decreased.3) The dentoalveolar characteristics of average angle class II1 malocclusion group showed that: U6 was distal tipping, Ul, L1 was labial inclined, the vertical dentoalveolar height of L6 decreased, the functional occlusal plane (FOP) deviated awayfrom the neutral occlusal axis (NOA), and rotated downward. The high- angle group showed: U6 was distal tipping, Ul was labial inclined too, and FOP deviated away from NOA severe degree. The low-angle group showed: the vertical dentoalveolar height of U6, L6 decreased, U6 was distal tipping, L6, L4, LI. Ul was labial inclined, the angle of FOP between NOA showed no significantly difference from normal occlusion group.4) In the average angle group, the anterior upper height was too long or the lower height was too short correspondingly. In the high- angle group, the anterior height was too long or the posterior height was too short correspondingly. The proportion of the parts of the anterior height was normal in the low- angle group. The anterior height was too short or the posterior height was too long correspondingly, the proportion of the parts of the anterior height was normal too.It was concluded that: There were different cranioficiodental vertical characteristics for class II1 malocclusion with different vertical type in adolescences. We should take different ways to control vertical dimensions.