The Clinical Research Of The Treatment Of Class â…¡ Division 1 Using Mini-implant Anchorage

[Objective]: To evaluate the effect of using mini-implant to treat the class II division 1patients and find the advantage compared to the traditional anchorage. To compare the effect of the self-tapping and self-drilling mini-implant as orthodontic anchorages.[Method]: 48 patients of Class II division 1 who visited in orthodontic department of Hefei stomatological hospital during 2010-2014 were divided into mini-implant anchorage group and traditional anchorage group randomly. The mini-implant group was divided into self-tapping group and self-drilling group.The maxillary first premolars and mandibular second premolars were extracted in two groups. The treatment was started using Dentaurum Roth brackets. The domestic mini-implants were inserted into the mucogingival junction of maxillary second premolar and first molar to adduct the anterior teeth. The traditional TPA and face-bow were used in control group.The cephalometric films were taken before and after treatment. The indexes of hard tissue and soft tissue were analyzed using t-testing and Chi-square test of SPSS13.0software. The statistical differences were compared between the indexes of the before and after treatment、the treatment group and control group 、 the self-tapping and self-drilling mini-implant groups.[Results]:(1) The change of hard tissue:The change of the jaw: after the treatment the SNA angel、Go Gn-SN angel increased by different levels while the SNB angel decreased slightly. The variations of SNA angel were more in mini-implant group, however the variation of Go Gn-SN angel and OP-SN angel were less. It prompted that mini-implant could help to adduct the maxillary bone and control the occlusion plane and mandibular plane.The change of teeth: after the treatment, the UI-SN angle、the distance of U6-PP、U1-Y、L1-Y、U1-PP were increased while the U1-L1 angle、the distance of U6-Y 、L6-Y were decreased statistically(p<0.05).According to the results of t-test analysis, the variations of UI-SN angle、U1-L1 angle、the distance of U6-PP、U1-Y、L1-Y was more in mini-implant group while the variation of the U6-Y distance was less. It meant that mini-implant group were obtained more effectiveness in adducting the front teeth and controlling the molars movement.(2) The change of soft tissue: the NLA angle increased while the distance of E line-UL and E line-LL decreased before and after treatment in both groups. The statistical difference value was more obvious in mini-implant group( p<0.05). It meant that the nasolabial angle increased、while the upper and lower lip’s protrusion decreased in both groups. The profiles of patients in mini-implant group were improved more and they tend to be more straight.(3) No statistical differences were found in each indexes between self-tapping mini-implant group and self-drilling mini-implant group.(4) The period of treatment was shortened by 4 months using mini-implant compared to traditional anchorage( p<0.05).[Conclusion]:(1) Using two kinds of anchorage to treat class II division 1 can both obtain satisfactory results.(2) Compared to traditional anchorage, better results were obtained by mini-implant in adducting front teeth、controlling the molars movement and improving the profiles.(3) Mini-implant can shorten the period of the treatment.(4) There are no statistical differences between self-tapping mini-implant and self-drilling mini-implant.