| The process of orthodontic treatment is to change the position and angle of the tooth,and move it to the ideal position of function and aesthetics,so that the soft tissues such as the nose,lips,chin and so on will change accordingly,making mouth and maxillofacial more harmonious and beautiful.The occlusal plane(OP)is formed with the establishment of occlusion,and changes with the change of occlusion,thus orthodontic treatment will have a certain impact on the occlusal plane.Meanwhile the change of occlusal plane will affect the position of the mandible,the stability of post-orthodontics,the masticatory function and the temporomandibular joint and so on.Therefore,the change of the occlusal plane after the orthodontic treatment is worthy of orthodontic doctors' attention.For class II Division 1 adult patients with high angle,the success of orthodontic treatment is to control the vertical direction,leading the mandible to rotate counterclockwise which can solve both the vertical and sagittal discordance.A large number of studies have found that in the process of craniofacial growth and development,with the reduction of the mandibular plane angle,the occlusal plane flattened continuously.While Fushima etc.pointed out that the clockwise rotation of the mandible was accompanied by a steep occlusal plane.It is the occlusal plane and the mandibular position connect so closely,so that the control of the occlusal plane is particularly important for the treatment of class II Division 1 adult patients with high angle.In recent years,mini-implant anchorage has been widely used in clinic because of its advantages such as small size,simple operation,small foreign body sensation,and no need of patient cooperation.Compared with traditional anchorages,the mini-implant anchorage show enormous advantages in vertical control,but these advantages are unclear in occlusion plane.Objiective: The inclination of the occlusal plane(OP)is related to the position of the mandible and facial types?The aims of this research were to determine if there were any differences in the changes of occlusal plane and mandibular plane angle with mini-implantanchorage and traditional anchorage in treatment of adult patients with Class II division 1 hyperdivergent malocclusion after the extraction of maxillary and mandibular first premolars ?Material and method:1.Material The subjects in this study included 40 adult patients with Class IIdivision 1 hyperdivergent malocclusion?All were required extraction of maxillary and mandibular first premolars ?The subjects were divided into two groups.Group 1 subjects treated with implant anchorage(20payients,1boys and 19girls)and group 2 subjects treated with conventional anchorage(20patients,3boys and 17girls).The ages are 15-30 years in two groups?2 method1)there were 13 representative measurement indexes related the changes of occlusion plane and mandibular plane angle?Lateral cephalograms of each patient were measured and analyzed.2)All statistical analyses were performed with SPSS software(version 19.0).All the data fitted normal distribution.the mean and standard deviation values were calculated.A paired-samples t test was used to determine the significance of the treatment changes between the pre-treatment and post-treatment within each group.Treatment changes between the 2 groups were compared with an independent-samples t test.And the levels of statistical significance were ?=0.05Results1 Changes in the related indexes of teeth1.1Comparison before and after treatment of the mini-implant Anchorage group(G1):the maxillary first molar(U6-PP)were intruded 0.16(±0.70)mm,the maxillary incisor(U1-PP)were intruded 0.62(± 0.62)mm,the mesial movement of maxillary first molar were 0.07(±0.16)mm;mandibular first molar(L6-MP)were extruded 0.09(±0.23)mm,mandibular incisors(L1-MP)were extruded 0.01(±0.74)mm,the plane angle(OP-SN)decreased 0.10(±1.11)°;Compared with after treatment,there were no significant differences of these indexes(P>0.05),except for U1-PP(P<0.05).1.2 Comparison before and after treatment of the traditional anchorages groups(G2):the maxillary first molar(U6-PP)the mesial movement of maxillary first molar were 1.41(±1)mm(U1-PP),maxillary incisor were extruded 0.94(±1.27)mm,the mesial movement of maxillary first molar were(2.56±1.46)mm,mandibular first molar(L6-MP)were extruded 0.08(±0.27)mm,mandibular incisors(L1-MP)were intruded 0.11(±1)mm,the occlusal plane increased 2.40(±1.48)°;compared to before treatment,excepted the(L6-MP?L1-MP),the measurement indexes were statistically significant(P<0.05).1.3 Comparison of the treatment results between G1 group and G2 group : UI-PP,U6-PP,U6-SV,the differences have statistical significance(P<0.05),reveling that the mini-implant anchorage compared to traditional anchorages for the sagittal and vertical control of maxillary molars and incisors are more effective and can control the occlusal plane effectively.While LI-MP and L6-MP,There were no significant difference(P>0.05),indicating that the two groups in the treatment process,effectively reduced the extrusion of molars and incisors,which was beneficial to the treatment of the high angle cases.2 Changes in jaw indexes2.1 Comparison before and after treatment of the mini-implant Anchorage group(G1): SNA angle decreased(0.93±1.09)°(P<0.05);SNB angle decreased(0.15±0.56)°(P>0.05);mandibular plane angle(MP-SN,Go Gn-SN)were respectively decreased(0.08±1.21;0.03±0.94)°(P>0.05);Y axis angle reduced(0.35±1.08)°(P>0.05),LFH decreased 0.54(±2.45)mm(P>0.05).SNA angle decreased and the difference has statistical significance,indicating implant anchorage for anterior teeth retraction,with maxillary alveolar bone remodeling.Although the difference of some indexes reflecting mandibular position and rotation,such as SAB angle,mandibular plane angle,Y axis angle,LFH and so on,were not statistically significant.In the clinical application of mini-implant,the mandible can be showed anticlockwise trend,reflecting its advantages in vertical control.2.2 Comparison before and after treatment of the traditional anchorages groups(G2):SNA angle decreased(0.85±0.74)°,SNB angle decreased(1.23 ±0.88)°,while the Y axis angle increased(1.20±1.36)°,mandibular plane angle(MP-SN,Go Gn-SN)were respectively increased(1.18±1.03;1.00±0.99)°,LFH increased 0.94(±1.92)mm.All indexes have significant difference.SNA angle decreased,indicating that when using the traditional anchorages for anterior teeth retraction,the maxillary alveolar bone reconstruct.However,the mandible can be showed clockwise rotation,which has adverse affects to the treatment of class II Division 1 high angle cases.2.3 Comparison of the treatment results between G1 group and G2 group : except for the SNA angle,the indexes were statistically difference,which showed that when retracting the anterior teeth,the maxillary alveolar bone had certain reconstruction in mini-implant anchorages group and traditional anchorages.What's more,compared with the traditional anchorages,the mini-implant anchorage has absolute advantages in vertical direction control.After the treatment of mini-implant anchorage,the mandible showed anticlockwise trend.Conclusion:1.In the aspect of axial and vertical control,the mini-implant anchorage has the absolute advantage compared with the traditional anchorage.2.In the control of the occlusal plane,compared with the traditional anchorage,the mini-implant anchorage can be used to control the occlusal plane effectively by showing a trend of counterclockwise rotation.3.In the terms of the mandibular plane angle: the anchorage has a good control of the occlusal plane,the mandible appears counterclockwise trend,mandibular plane angle,Y angle,the higher are small.Owing to the good control of the mini-implant anchorage to the occlusal plane,the mandible has a tendency of counterclockwise rotation,and the mandibular plane angle,the Y axis angle,and the lower facial height are all small.It can solve the problems of both sagittal and vertical directions of class II Division 1 malocclusion patients with high angle,making the profile more harmonious and beautiful. |
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