| The correction of Class II malocclusion is one of the most common problems facing the orthodontist, with an estimated one-third of all orthodontic patients treated for this condition. It is well known, however, that Class II malocclusion is not a single diagnostic entity, but, rather, can result from various skeletal and dentoalveolar components. Class II malocclusions form a heterogeneous group of patients that represents a significant portion of the patients who typically present for orthodontic treatment. Resolving Class II molar relationships by distalizing maxillary molars may be indicated for patients with maxillary dentoalveolar protrusion or minor skeletal discrepancies.As indicated previously, an optimal time to move molars distally with these appliances is the mixed dentition stage of development (preferably the late mixed dentition) before the eruption of the second molars. Movement of the molars is the fastest and anchorage loss is the least when compared with treatment after the eruption of the second molars.The purpose of this study was to assess the eruption of maxillary second molar related to different ways for the first maxillary molar distalization.The sample for this analysis of the molar distalizing appliance consisted of consecutively treated Class II orthodontic patients (The second morlars are not erupted)obtained from the department of orthodontics, the Fmmu. The mean age of the sample at the time of the initial records was 12.2 (SD ± 2.3).The patients were divided into 6 groups, according to the existing of the germectomy of third molar and the way of distalizng molars.We used three ways(Distal Jet; Face bow; GMD) to distal the maxillary first molar. Molar movement in the horizontal plane was monitored by taking alginate impressions and making dental casts both at the outset of therapy (T1) and after removal of the distal molar appliance (T2). Changes in the sagittal plane were determined by measuring relevant parameters in the cephalograms made both at Tl and T2.First part: If there have not the germectomy of the third molar.In the group of Distal Jet , Measurement of the maxillary dental casts showed that the gain in transverse arch width in the first and second molar region between the mesiobuccal cusp tips and the distobuccal cusp tips proves that not only distobuccal rotation but also vestibular drift of the unhanded second molars were happened, and expansion and mesiobuccal rotation occurred in the first molar region.In the sagittal plane, cephalometric analysis for identifying any changes showed that tipping of the second molar was much more pronounced when the first molar was distalized.The same things also happened in the group of Face-bow, only the measurement of the maxillary dental casts showed that the distobuccal rotation happened in the first molar region and mesiobuccal rotation occurred in the unhanded second molars.In the group of GMD, Measurement of the maxillary dental casts showed that only vestibular drift of the unhanded second molars were happened, and the rotation of the second molar were not happened. In the sagittal plane, cephalometric analysis showed the tipping of the second molars were much more marked.Second part: If there have the germectomy of the third molar.In the groups of the three ways to distal molar, it shows that in the distalization direction, a tooth bud acts on the mesial neighboring tooth in the same way as a fulcrum. It proved that tipping of the second molar was much more pronounced when the third molar was still at the budding stage.The rotation and vestibular drift of the unhanded second molars were also happened in the same way to the group of First part.but the level were much more less. A third molar bud seemed to place restriction on the degree of vestibular drift and rotation .In the sagittal plane, cephalometric analysis for identifying any changes showed that, in the distalization direction, a tooth bud acts on the mesial neighboring tooth in the same way as a fulcrum. It proved that tipping of the first molar was much more pronounced... |
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