Clinical Study Of Comparison Of Treatment Effects Produced By The Dynamax Appliance And The Twin Block Appliance

Objective: To evaluate the soft and hard tissue changes in curing class II division 1 mandibular retrusion cases with Dynamax or Twin block(TBA); analysis the relativity between bone age changes and the changes of the mandible and the morphology changes for the mandibular bone in the treatment; and study the effects for oropharyngeal and hyoid position of the two functional appliances treatment; and provide a new effective treatment methods and theoretical basis for mandible retruding cases in orthodontics clinical practice.Methods: Selecting 45 Class II division 1 malocclusion subjects whose hand-wrist radiographs were in FG-G stage. 15 of them who had abandoned treatments were put in the control group(C) and were observed for 12 months; and the other 30 cases were randomly divided into two groups, one group received Dynamax appliance treatment (D group), the other received TBA treatment (T group). Treatment and holding time for 12 months. Selecting 22 soft and hard tissue variables for metrical targets, 11 variables for oropharyngeal and hyoid, 5 variables for mandible to measure, and to measure bone by C3, C4. The control group of the third experiment were the 15 persons whose maxillary and mandible were normal and the hand-wrist bone were in FG-G stage and were observed for one year, then measured for oropharyngeal and hyoid variables. All objects were taken head lateral projections with X-ray before and after treatment (observation). Scanning the projections into computer and using special software winceph7.0 to measure. Analyzing the acquired data of three groups statistically with SPSS 11.0.Result: Changes for soft and hard tissue: There were significant differences of the changes of SNB(°),Co-Gn(mm),ANB(°),Wits(mm),U1.NA(°),U1-NA(mm),L1.NB(°),Overjet(mm),Overbite(mm),Ns-Sn-Pos(°),Ls-E(mm) between the two experimental groups and control group (P<0.05), and there was no significant differences between the two experimental groups(P>0.05). There were significant differences of the GoGnSN(°), Cm-Sn-Ls(°) changes between the group D and the other groups (P<0.05). There were significant differences of the PFH(mm), AFH(mm) changes between the group T and the other groups (P<0.05) and the S-Ns-Si(°) changes between three groups (P<0.05). The changes of mandibular and the relativity analysis between the changes and bone age: There were relativity of changes between bone age and the total mandible length, the ramus length ,the mandibular plane angle, the mandibular angle and bone age when Dynamax functional appliances were used for the treatment, the total mandible length, the ramus length and mandibular plane angle when TBA functional appliances were used for the treatment. There were relativity of changes between the total mandible length, the ramus length and the corpus length when there was no functional appliances used. There were difference of mandibular changes between the two experimental groups. D group showed that the mandibular growth was not only in the vertical but also forward to back and the mandibular plane circumrotated backward. T group showed that the mandibular growth was only in the vertical, and the mandibular plane was almost no rotation.The changes of oropharyngeal and hyoid: the two experimental groups were different with the control group (the normal group) in many variables before the treatment. It was almost consistent between the two experimental groups and the control group in all variables except for U-PP(mm) and H-Ptm(mm) after the treatment.Conclusion: 1. For Class II Division 1 patients using Twin block or Dynamax in the early treatment could effectively improve facial appearance, and make the soft and hard tissue side face become normal. It were almost the same effect for the two functional appliances.2. The changes of the Class II division 1 patients when using the two appliances treatment were different. The Dynamax could make mandibular circumrotate backward, mandibular plane angle become larger, and the condyle grow not only in vertical but in sagittal. While the Twin block made the mandible grow in vertical and the mandibular plane angle unchanged.3. There were relativity between bone age changes with the vertical and sagittal growth of the mandible when Dynamax functional appliances were used for the treatment.4. The oropharyngeal bones were obviously different between the Class II Division 1 patients with mandibular retrusion and the persons whose mandibular developed normally, but they were almost the same after the treatment. The effects were almost the same of the two functional appliances Dynamax and Twin block.