| BackgroundIn recent years,with the continuous improvement of people’s oral health awareness,more and more patients not only pay attention to dental health,but also hope to have a perfect smile and perfect appearance,so many patients are willing to accept dental correction.Clinically,patients who complain that " dibaotian" affects the aesthetic or occlusal function often come to ask for correction,the so-called class Ⅲ malocclusion,and its typical clinical manifestations are mesial relationship of molars,anterior crossbite,mandibular protrusion and/or maxillary retrusion and concave lateral appearance.For the treatment of class Ⅲmalocclusion,the methods are depended on different stages and the severities.At the early stage,blocking and functional treatment are often adopted;serious skeletal class malocclusion requires Ⅲorthodontic-orthognathic surgery,while for mild or moderate skeletal class Ⅲmalocclusion,disguised treatment is adopted.When clinicians design orthodontic treatment plans,extraction and non-extraction have always been a controversial topic.However,many patients want to correct their teeth on the basis of keeping healthy teeth,so they are unwilling to extract teeth.Orthodontic treatment needs clearance to adjust teeth,and the management of clearance needs anchorage as the basis.Especially when correcting mild or moderate skeletal class Ⅲmalocclusion,it is necessary to strictly control mandibular anchorage.The birth of implant anchorage and its wide application,which makes this control possible.Therefore,for patients with mild or moderate skeletal class malocclusion,the measuremenⅢ t and analysis of the posterior space of dental arch and the analysis of the therapeutic effect of implant anchorage on distal dentition have guiding significance for clinical work..ObjectiveIn this study,the patients with mild or moderate skeletal Class Ⅲmalocclusion were choosed,and and they were reluctant to accept extract teeth and were reluctant to accept orthodontic-orthognathic surgery.MBT fixed orthopedic techniques and miniscrew anchorage were applied to distalize mandibular total arch after analyzing the space of dental arch.X-ray cephalometric analysis was performed on the lateral cephalograms before and after treatment.The soft and hard tissue changes before and after correction were observed.The mandibular incisors and the mandibular molars were examined from the sagittal and sagittal directions.The model measurement was examined to analyze the change of dental arch width.All measurement items were evaluated the correction effection.MethodsSeventeen patients with mild or moderate skeletal Class Ⅲmalocclusion were choosed,and they were reluctant to accept extract teeth and were reluctant to accept orthodontic-orthognathic surgery including 12 males and 5 females.The age was(23.80±3.86)years old.Radiographic cephalometric projection and panoramic radiography were used to analyze the amount of mandibular total arch distalization.The treatment plan was carried out after analysing the posterior margin space of dental arch.MBT fixed orthopedic techniques were applied to this study.Firstly,MBT brackets were adhesived,and the dentition was aligned to 0.019″×0.025″ stainless steel square wire,then the traction hooks were fixed between the mandibular arch cuspids and lateral incisors.Finally,the miniscrews were implanted in the buccal lateral oblique ridge region of mandibular second molar,and the rubber chains or NiTi springs were fixed between the miniscrew implant and the traction hook to distalize mandibular dentition,each side of the traction force was above 200 g.Geometric sketchpad 5.0 software was used to plot,mark,and measure the research items before and after the treatment.The center distance vernier caliper was used to measure each research item before and after the treatment.The data were processed with SPSS 21.0 software package.Results1.The measurement and analysis of panoramic radiography: before treatment,the posterior margin of dental arch was(7.84±1.70)mm;after treatment,the posterior margin of dental arch was(3.59±0.73)mm.The difference was(﹣4.25±1.91)mm,and the difference was statistically significant(t ﹦ ﹣ 9.141,P ﹦0.001).2.The measurement and analysis of radiographic cephalometric projection:(1)The amount of soft and hard tissue changed: before and after treatment,the SNB angle decreased by(0.99±1.20)°,the ANB angle increased by(1.91±1.02)°,the SN-OP angle decreased by(3.83±3.42)°,The Wits value decreased by(6.40±4.56)mm,the Pog-F decreased by(0.71±1.20)mm,and the difference was statistically significant(P<0.05).The FH-MP angle increased by(1.43±3.03)°,the “6b”increased by(1.02±2.22)mm,and the difference was not statistically significant(P > 0.05).The Ls-E decreased by(1.20±1.06)mm,the Li-E decreased by(1.94±1.32)mm,the Pg-F decreased by(1.75±2.41)mm,the NLA angle increased by(4.78±6.92)°,the LSP angle decreased by(6.68±7.89)°,and the difference was statistically significant(P<0.05).(2)The amount of mandibular first molars changed: before and after treatment,when the Y axis was used as the reference system,the mandibular first molar crowns distalized(3.88±1.30)mm and the roots distalized(3.34±1.40)mm in the sagittal direction;when the D axis was used as the reference system,the mandibular first molar crowns distalized(2.93±2.43)mm and the roots distalized(2.11±2.55)mm in the sagittal direction,the differences were statistically significant(P<0.001).When the X axis was used as the reference system,the mandibular first molar crowns impressed(0.72±0.85)mm in the vertical direction;when the C axis was used as the reference system,the mandibular first molar crowns impressed(0.68±0.86)mm in the vertical direction,the differences were statistically significant(P<0.001).In addition,there was no significant difference in the angles α and γ of the first mandibular molar(P>0.05).(3)The amount of mandibular incisors changed:before and after treatment,when the Y axis was used as the reference system,the mandibular incisors distalized(4.12±1.92)mm,and the roots distalized(3.95±2.71)mm in the sagittal direction;when the D axis was used as the reference system,the mandibular incisors distalized(4.18±1.60)mm,and the roots distalized(3.72±1.49)mm in the sagittal direction,the differences were statistically significant(P<0.001).When the X axis was used as the reference system,the mandibular incisors extruded(1.40±1.52)mm in the vertical direction;when the C axis was used as the reference system,the mandibular incisors extruded(0.83±0.82)mm,the differences were statistically significant(P<0.001).In addition,there was no significant difference in the angles β and θ of mandibular incisors(P>0.05).3.The measurement and analysis of model measurement:before and after treatment,the width of the anterior segment of the dental arch reduced by(1.28±1.48)mm,and the width of the posterior segment of the dental arch increased by(1.06±1.75)mm,the difference was statistically significant(P<0.05).The width of the mid-arch reduced by(0.15±2.17)mm,there was no statistically significant difference(P>0.05).Conclusions1.Under the condition that sufficient space was provided in the posterior boundary of the dental arch,it was feasible to distalize the mandibular total arch.2.It was achievable to distalize mandibular dentition by using miniscrew anchorage.3.By distalizing the mandibular dentition,the mild or moderate skeletal Class Ⅲ malocclusion were corrected to normal overbite and normal overjet.The sagittal misalignment was solved,the vertical and horizontal directions can be effectively controlled,and the soft tissue lateral appearance can also be improved. |
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