The Comparison And Analysis Of FMA In Class Ⅱ DivisionⅠ Malocclusion With Different Vertical Skeletal Types Before And After The Treatment

Objective:To investigate the variations of FMA in Class Ⅱ division 1 malocclusion patients with different vertical skeletal types before and after the orthodontic treatment,and to provide reference for clinical treatment.Methods:30 finished cases of Class Ⅱ division 1 malocclusion patients were selected from the orthodontic department of the Second Affiliated Hospital of Dalian Medical University,who were all treated with straight wire appliance.Their ages was between 18-25 years old,Among these patients,their upper and lower jaw bones developed normally in sagittal space,and had different vertical facial types.The course of treatment was limited to 30 months.Taken lateral films before and after treatment in the same conditions,and the results were measured by the same operator with the software Veceph5.0 in a definite time period.Measured each X-ray film three times and averaged the numerical value.According to the values of FMA(the angle of Frankfort horizontal plane and mandibular plane),these patients were divided into three groups: FMA > 28°for the high angle group,FMA < 22°for the low angle group,and 22°≤FMA≤28°for the average angle group.Measured the figures of FMA,Occ Plane,Index Post Face Height/Ant Face Height and Z angle before and after the treatment.All of the data were analyzed by SPSS17.0 statistical software,and the indexes and changes before and after the treatment were compared by t-test,Then discussed and evaluated the changes of FMA before and after the orthodontic treatment.Results: Comparing the values before and after treatment in the high angle group of Class II division 1 by t-test,we find that the P values of FMA,Occ Plane,Index Post Face Height/Ant Face Height and Z angle are generally greater than 0.05.Thus the difference has no statistical significance and there is no significant difference in the changes of FMA.While in the average angle group of Class II division 1,the P value of FMA is 0.004.The difference is statistically significant which means there is significant difference in the changes of FMA.The mandibular plane has the trend of clockwise rotation.The P values of Occ Plane,Index Post Face Height/Ant Face Height and Z angle are greater than 0.05,so the difference is not statistically significant.In the low angle group of Class II division 1,the P value of FMA is 0.002 and the difference is statistically significant.The P value of Index Post Face Height/Ant Face Height is 0.001,so the significant change is statistically significant.There are no significant changes in Occ Plane and Z angle.Therefore,the mandibular plane of the low angle group of Class II division 1 has the trendency of clockwise rotation.Conclusion: In the high angle group of non-osteal Class II division 1 patients,the mandibular plane doesn’t have changed markedly without oral anchorage and implant anchorage.The value of FMA could have increased after the orthodontic treatment in the average angle group of non-osteal Class II division 1 patients,and the mandibular plane has the trendency of clockwise rotation.In the low angle group of non-osteal Class II division 1 patients,the value of FMA has increased and the mandibular plane has the trendency of clockwise rotation without absolute anchorage.