| Objective: The thesis compares the X-ray lateral cephalometric radiographs changes in skeletal class III malocclusion patients with two kinds of maxillary protraction appliances before and post treatment as well as the predicted VTO to evaluate the treatment effect and credibility of VTO prediction method,then guide the clinical selection of this kind of appliance and the reasonable application of VTO prediction method.Methods: A total of 46 malocclusion patients(18 males and 28 females)with skeletal class III were selected.The age ranged from 8.6-12.8 years(mean 10.9 ±1.3 years).The maturity of Cervical vertebra was in the period of Cvs1-Cvs3 before or at the peak of growing development.All the subjects were divided into two groups: group A with active pads and group B with fixed rings.All the patients took lateral cephalometric radiographs before treatment(T1)and immediately after treatment(T2)and the VTO prediction diagram(T3)based on the X-ray lateral cephalometric radiographs before treatment(T1).SPSS 17.0 statistical analysis software was used to analyze the changes of cephalometric analyysis before treatment,after treatment and in VTO prediction.The statistical methods used in this study are paired t — test and independent t — test,to compare in interior-group and inter-group data,evaluate the treatment effect of the two kinds of appliances and the difference between the VTO prediction method and the practical treatment effect,and the difference was statistically significant if p< 0.05.Results: 1、There were significant changes in bone tissue,teeth and soft tissue after maxillary protraction.The maxilla of all two groups moved ahead after orthodontics,and all the mandibles rotated backwards and downwards;the 1abial inclination of the maxillary anterior teeth,the lingual inclination of the mandibular anterior teeth,and the changes of protrusions in upper and lower lips resulted in a better facial shape.2、Thedifferences between two groups were significant(P<0.05): Ptm-A、MP-SN、MP-FH、ANS-Me、UI-SN、LI-MP、G-Sn-Pg and the upper lip protrusion showed that group B had more maxilla movement and lower mandibular rotation than group A,and the lower mandibular rotation was smaller in group B than in group A and the less anterior low facial height,the upper and lower anterior teeth tilted less slightly,and the upper lip protruding degree improved more significantly.3、There was no significant difference between the VTO prediction of bone tissue in group B and true treatment results(P>0.05),but there was significant difference in group A(P<0.05),which showed more maxillary ahead movement and less mandibular posterior rotation;For the prediction of the teeth,both the two groups showed more lingual inclination in the lower incisors;For soft tissue prediction,there was no significant difference between the two groups(P>0.05),except the nasolabial angle.4、There was significant difference(P<0.05)in VTO prediction between groups except bone tissue,but there was no significant difference in tooth and soft tissue(P>0.05).Conclusion:1、Both the maxillary protraction therapy in skeletal class III patients with two kinds of appliances have significant orthopedic effect.2 、 There was no significant difference in the treatment course between the two groups,but there was more bone effect and less tooth effect in the fixation group than in the active group.The improvement of soft tissue profile was also more significant.3、The VTO prediction of the changes of hard tissue after maxillary protraction in the fixed group was more reliable than that of the active group;the VTO prediction of tooth and soft tissue changes had some credibility in both groups,but the prediction for lower incisor and nasolabial angle were deviated from actual results. |
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