Treatment Of Children With Skeletal Class Ⅲ Malocclusion Showing Skeletal Protruding Mandible—Type Ⅲ Intermaxillary Traction Combined With Maxillary Screw Expander Appliance

Objective:To explore the clinical effect of type Ⅲ intermaxillary traction combined with maxillary screw expander appliance on children with skeletal class Ⅲ malocclusion showing skeletal protruding mandible.Methods:24 children with skeletal class Ⅲ malocclusion showing skeletal protruding mandible(including 13 males and 11 females,with an average age 5.7 years)were selected.The development of mandible was restricted using type Ⅲ intermaxillary traction and the positions of mandible and maxilla,as well as dentition,were adjusted interactively.The positions of maxillary anterior teeth and maxilla were changed using maxillary screw expander appliance.If the children were also with maxillary retrusion,then adding rapid maxillary expansion combined with maxillary protraction to pull maxilla forward.The projections of lateral radiographs before and after treatment were compared using WinCeph9.0 projection analysis software.The measurement system was established and 17 markers,which could reflect the profile of mandibular hard tissues and maxillofacial hard and soft tissues,were selected to detect and evaluate the mandibular development,lateral appearance difference and axial changes of upper and lower anterior teeth before and after treatment.The obtained data was statistically analyzed with paired t test and correlation analysis using SPSS software.The inspection level a=0.05 and P<0.05 means significant difference.After treatment,patients whose cross bite were relieved were labeled as ones with successful treatment and they had further consultation six months later to assess the stability of the treatment.Result:1.After treatment,the intersecting angle(Ul-SN)of upper incisor long axis and SN plane significantly increased(p<0.001),while the intersecting angle(L1-MP)of lower incisor long axis and mandibular plane remained constant(p>0.05).The crossing angle(U1-NA)of upper incisor long axis and nose point-upper alveolar point connection significantly increased(p<0.05),while the crossing angle(L1-MP)of lower incisor long axis and nose point-upper alveolar point connection remained constant before and after treatment(p>0.05).2.Mandibular measurement items,including ∠SNB,facial angle(NP-FH),and MP-FH,remained constant before and after the orthodontic treatment(p>0.05).Y axial angle significantly increased(p<0.05).Maxillary measurement items,including Z SNA and NA-PA,significantly increased.While ANS-Ptm and Go-Gn showed no significant increase before and after the orthodontic treatment(p>0.05).3.The occlusal relationships of upper and lower molars were commonly measured with Wits value and ∠ANB which are significantly increased after treatment(p<0.001).4.After treatment,oral anti-occlusion of all the children was relieved and the 17 patients showed occlusal stability without recurrence in the diagnosis six months later.conclusion:There was a significant correction effect of type Ⅲ intermaxillary traction combined with maxillary screw expander appliance on children with skeletal class Ⅲmalocclusion showing skeletal protruding mandible and the abnormal position of upper and lower anterior teeth was improved.The anterior teeth anti-occlusion of all patients was relieved and the treatment efficacy tracked six months later was stable.After treatment,the position relationship between upper and lower jaw changed significantly,the maxillary protrusion increased and the mandibular growth was obviously restricted.The axial angle of maxillary anterior teeth changed significantly,while the axial angle of mandibular anterior teeth showed no significant change.