| The objects of this research were AngleⅢmalocclusion osteal cross bite patients who were treated by maxillary protraction therapy combined with rapid palatal expansion in the Department of Orthodontics, Stomatological College of FMMU, and they were divided into three different groups by age: the 3～6 years group, the 7～10 years group and the 11～13 years group. Through comparing and analyzing the photographs of Cephalometrics before orthodontics, after orthodontics and two years after orthodontics, we can probe into the optimal period for treating AngleⅢmalocclusion osteal cross bite patients with maxillary protraction therapy and the long period of stability after the accomplishment of orthodontics, and it can provide reference and theoretics for clinic practice and experiments.Results1. Compared with the condition before orthodontics, the maxilla of all the three groups moved ahead after orthodontics, at the same time ,all the mandibles rotated backwards and downwards. The points of A and ANS moved ahead obviously, the points of B and Pg moved downwards, the MAP and anterior low facial height were increased. The relationship between the maxilla and mandible was improved significantly, the angle of ANB was increased obviously, the labial inclination of the maxillary anterior teeth, the lingual inclination of the mandibular anterior teeth, the mesial shift of the mandibular and maxillary molars, the abnormal molar's relationship, and the overbite and overjet of anterior teeth were all corrected. Compared the three groups: after the treatment of maxillary protraction therapy for the patients of the three groups, the maxilla and the mandible were all changed a lot, but the angle of ANB among the three groups wasn't changed differently. The labial inclination of the maxillary anterior teeth of the 11～13 years group was changed the most ,and the 3～6 years group was the least, there was prominent difference among the three groups(P<0.05). The MAP and anterior low facial height of the 11～13 years group were increased the most, and the 3～6 years group was the least, there was prominent difference among the three groups too(P<0.05).2. Compared with the condition before orthodontics, two years after orthodontics, all the maxilla or mandible grew ahead and downwards. The points of A , ANS, B and Pg moved ahead obviously. The labial inclination of the maxillary anterior teeth, the lingual inclination of the mandibular anterior teeth, the relationship between the maxilla and mandible were all ameliorated distinctly. Compared the three groups: the maxilla of the 11～13 years group moved ahead less distance than the other two groups, there was prominent differenc(eP<0.05). But there wasn't difference between the 3～6 years group and the 7～10 years group. The anterior low facial height of the 11～13 years group was increased the most, and the 3～6 years group was the least, there was prominent difference among the three groups(P<0.05).3. After the orthodontics was finished, as the time went on , the maxilla continued to grow ahead, but the rate and quantity of mandibular growth were more than maxilla., the sagittal relationship between the maxilla and mandible tended to reoccur, the points of B and Pg moved ahead obviously, the angle of SNB was increased, the angle of ANB was decreased. The inclination of mandibular and maxillary anterior teeth was increased to an extent. Compared the three groups: the maxilla or mandible's forward shift of the 3～6 years group was bigger than the other two groups, the 11～13 years group moved the least, there was prominent difference among the three groups(P<0.05), and when it came to the labial inclination of the maxillary anterior teeth and the lingual inclination of the mandibular anterior teeth, the 3～6 years group was changed the most, the 11～13 years group was the least, there was prominent difference among the three groups(P<0.05).Conclusions1. The method of maxillary protraction therapy combined with rapid palatal expansion was effective for the treatment of three different age groups of AngleⅢmalocclusion osteal cross bite patients: the maxilla moved ahead, the mandible rotated backwards and downwards, the anterior low facial height was increased, the relationship between the maxilla and mandible ameliorated distinctly, the abnormal molar's relationship, the overbite and overjet of anterior teeth were all corrected. The bone of the 3～6 years group was changed the most, the upper and lower anterior teeth's compensated change of the 11～13 years group was increased the most, and the 3～6 years group was the least. According to this, the optimal period for maxillary protraction therapy is between 3and 6 years old, during the period, we can obtain the more skeletal change and the less teeth change.2. At the end of maxillary protraction therapy for the three different age groups, the position of the maxillas and mandibles was changed a lot, the interocclusal relation was improved, but the interocclusal sagittal relationship tended to recur, the chance of recurrence was the biggest in the the 3～6 years group, and the 11～13 years group was the smallest, compared with the other two groups, the stability after orthodontics of the 3～6 years group was the worst. Therefore, we select the time of 3-6 years old for orthodontic treatment, we have to consider the harmful consequence because of low stability after orthodontic treatment. To prevent the recurrence, it is suggested that we should take active measures to restrict the over growth of mandible. |
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