The Study Of Dental Arch And Basal Bone Morphology In Angle's Class Ⅱ, Division 1 Malocclusion

Objective: For provide a theoretical basis to clinic diagnosis and treatment, the purpose of this investigation was to study the dental arch and basal bone morphology in Angle's Class II, division 1 malocclusion by cephalometric and dental model measurement, and to discuss the relationship of the dental arch and basal bone morphology.Methods: a selection of 60 patients with Angle's Class II, division 1 malocclusion as the experimental group, 60 adults with individual normal occlusion as the control group, cephalometric and dental model were measured to compare the difference of dental arch and basal bone morphology. Another selection of 36 patients with Angle's Class II, division 1 malocclusion, including 12 patients with high-angle, 12 patients with middle angle and 12 patients with low angle, measure the dental arch and basal bone morphology of each sample and study the difference among three groups through analysis of variance.Results: 1. In Angle's Class II, division 1 patients, the medium and posterior parts dental arch width of maxillary were greatly narrowed.No evident difference of the width of dental arch could be found in anterior parts of maxillary,and in all parts of mandible.The dental arch length of maxillary and medium part of mandible were greatly longer. The basal bone width of maxillary and mandible were normal. The basal bone length of maxillary was increased greatly and the mandible was normal. 2. The dental arch width of maxillary showed significant difference among the high-angle, middle- angle and low-angle groups. The medium and posterior parts dental arch width of mandible in the low-angle group were greatly increased than in the high-angle and middle-angle group. The dental arch length of maxillary and mandible showed no significant difference among the three groups. The basal bone width in the intercanine and interpremolar regions of maxillary and mandible showed no significant difference among the three groups. The basal bone length in the maxillary and mandible also showed no difference. The maxillary inermolar basal bone width in the low-angle group were greatly increased than in the high-angle and middle-angle group. 3. The mandible clockwise in the high-angle group while counterclockwise circumrotatory in the low-angle group. The anterior facial height increased in the high-angle group, while posterior facial height decreased in it, in contrast with low-angle group. The faciolingual inclination of maxillary middle incisors showed no difference among three groups. The mandible middle incisors was vertical in the low-angle group, while labial inclinated in the high-angle group. 4. The dental arch was closely related to basal bone morphology in Angle's Class II, division 1 malocclusion, including low-angle and middle-angle groups. The maxillary dental arch length was related to basal bone lenth in the high-angle group. The mandible dental arch width was related to basal bone width also in the high-angle group.Conclusion: The pathogenesis of Angle's Class II, division 1 malocclusion is complicated. In the course of clinical treatment, we should pay attention to the coordination of dental arch and basal bone morphology in order to ensure long-term stability .There are different dental arch and basal bone morphology among different vertical facial skeletal types .We should take corresponding measures according to different characteristics.