| Objective:Base on the using of cervical headgear to study the effect and stability of the face mask of class III malocclusion.Methods:Collected 125 patients with skeletal Class III malocclusion treated by face mask in the Department of Orthodontics,from the First Hospital of Hebei Medical University during September 2015 to December 2017,nineteen patients with fixed appliance technology after face mask were selected from this kind of crowd as the control group,nineteen patients with cervical headgear combined with fixed appliance technology after face mask were treated as an experimental group.Selection criteria: All 38 patients have the following characteristics: at the end of mixed dentition or early permanent teeth,skeletal Class III malocclusion,mesioclusion and maxillary bilateral second molars have not yet erupted or are not yet established,at the peak of growth and development,patients with high compliance.The control group has 10 males and 9 females,experimental group has12 males and 7 females;the average age of starting treatment was 12.06±0.75 and 11.98±0.72 respectively,taking the cranial lateral cephelogram at the face mask before and after treatment,then measured 28 related data for comparative study and statistical analysis by SPSS24.0 software,last each measurement data is described with mean(X)± standard deviation(S).Based on the normal variance of the data after the face mask of the control group and the experimental group is performed carried out the homogeneity test,if the normal variance is equal,the group t test is performed.For the control group,the data of the post-treatment and end-of-treatment of the experimental group were respectively tested for homogeneity of variance,and if the normal variance was equal,the group t test was performed.An independent sample t-test was carried out on the change values of the control group and the experimental group respectively.Results:The relative positions of the upper and lower jaws have been effectively improved in all patients during the treatment,both teeth have reached a neutral relationship,the overlying coverage of the anterior teeth is restored to normal,the average course of treatment in the control group was 18.20±2.16 months.The average course of treatment in the experimental group was 22.54±2.55 months.In the control group,the SNA decreased by 1.62±1.32° on average and the experimental group decreased by 1.82±0.88° on average.The difference between the two groups is 0.20±0.71°,no statistical significance.Measurement items related to point A: NA-PA,NA-FH,C0-A,Ptm-A,A-N,A-Y,and there was no statistical difference between the experimental group and the control group.SNB control group increased by an average of 0.1±0.82°,and the experimental group increased by an average of 0.2±0.44°,and without statistical significance.In the control group,the ANB decreased by an average of 1.42±0.24°,and the experimental group decreased by an average of 2.02±0.74°,there was no statistical significance.The U1-SN control group increased by 4.58±1.43°,and the experimental group decreased by 2.92±3.28°,and the difference was statistically significant.The L1-MP difference was not statistically significant.The Ptm-6 control group increased by 1.62±0.70 mm,and the experimental group decreased by 2.25±0.72 mm,and the difference was statistically significant.Conclusion:Patients with skeletal Class III malocclusion using face-bow to remove maxillary molar have no significant effect on the outcome of anterior traction,the effect of distal molar removal is obvious after the treatment: each side of face-bow with 300-500 g of traction,wear 12-14 hours a day,the method can significantly reduce the lip inclination of upper incisor,but no significant effect on the position of the maxillary bone. |
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