| The Angle ClassⅡdivision 2 malocclusion is common clinically. Its frequency lies between 5% and 8%. Except the molars are in distoclusion, the ClassⅡdivision 2 malocclusion is characterized by a reduced overjet, the retroclined incisors and a closed bite. Sometimes it is also accompanied with the crowding of teeth. The treatment approach selected for the patients can not just be according to the crowding degree of the dental arch. After advancement of the maxillary anterior teeth to solve the retroclination of the upper central incisors and the closed bite, enough gaps could be got in the maxillary and mandible dental arch. The crowing of teeth could be solved to some extent. The treatment would be more difficult if tooth extraction were made without being cautious. The lower anterior teeth also shoud be advanced to establish normal overjet. For this reason to exract or not extract must be considered thoroughly.The aim of this study was to compare the clinic deta of the classⅡdivision 2 malocclusion patients using the method of radiographic cephalometry and to analyze the therapeutic effect. Thus we can search for the approach to classⅡdivision 2 malocclusion. The study can be beneficial for the diagnosis and the treatment design of the classⅡdivision 2 malocclusion.The content of the study:Materials and methods:The classⅡdivision 2 malocclusion group was selected according to the characteristics of this malocclusion: patients with permanent dentition, without absence of tooth and orthodontic treatment history. The first molars are in distal relationship. The upper incisors are retruded. The patients are with a closed bite. The crowding degree of maxillary teeth: 5.63±4.44mm; The crowding degree of mandible teeth: 5.16±3.25mm. All the patients were treated with non-extraction. In 12 of this casesⅡintermaxillary traction were used, 9 used the removable appliances, 4 used the face-bow to make distal displacement of the posterior segment.The first study:To make cephalometric analysis on lateral projection.The skeletal measurement item: SNA,SNB,ANB,NA/PA,Pg-NB,FH-NP,N-ANS,ANS-ME,MP/SN,MP/FH,Y;The dental measurement item: U1-NA,U1/NA,U1/SN,U1/PP,U1A-PtV,U1E-PtV,L1-NB,L1/NB,L1/MP,L1A-G0(MP),L1E-G0 (MP),U1/L1,U1-PP,L1-MP,U6-PP,L6-MP,L6/MP;The soft tissue measurement item: UL-E,LL-E,UL-LL.Result: After treatment the 20 patients all got good therapeutic effect. Average course of treatment is 16.54±5.91 months. The longest time is 31 months and the shortest one is 8 months. The measured value we got were in statistical significance.Conclusions: The teeth abnormality and disharmony of jaw in vertical and soft tissue profile of classⅡdivision2 malocclusion were improved well by non-extraction treatment.The second study: To make molar angulation changing analysis on panoramic radiographs:to measure the angles between the first molar line and interorbital line: ULOrb, UROrb, LLOrb, LROrb. Because of the abense of such kind of literature, the present study could just be a exploratory one.Result: After the non-extraction treatment, the classⅡdivision 2 malocclusion relation improved. The angulation of first molars were changed, which is in statistical significance.Conclusions: Through non-extraction treatment, The angulation of first molars were improved., which supports the conclusions of the first study. |
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