Case Report:effects Of Early Class ? Intermaxillary Elastic On The Treatment Of Skeletal Class ? Malocclusion

Objective:By introducing a case report of skeletal Class ? malocclusion which corrected by the combination of RME,SL brackets and early intermaxillary short class ? elastics,and analysing the changes between pre-treatment and posttreatment,to discuss the outcome of the methods of non-surgical treatment in this report and its mechanisms.Methods:A case of 14 years old male with skeletal Class ? malocclusion combined with posterior crossbite.Patient's description:Angle ? malocclusion,skeletal Class ? malocclusion with a deficient maxilla,an overgrowth of the mandible,Class ? canine and molar relationships on both sides,edge to edge bite with an open bite tendency,bilateral crossbite with an narrowed upper arch and a widen lower arch,and a1 mm deviation of the mandibular middle line to the left.The curve of Spee is deep.The deficiency of space in the upper arch is 4.5mm,in the lower arch is 6mm.With the consideration of patient's chief complaint,medical history,the analysis of model and X-ray,and the request of patient,the two-phases of treatment plan was confirmed:Firstly,simulating the growth of maxilla with orthopedic force;secondly,do the fixed appliance treatment with orthodontic force.Compare the outcome of pre-treatment,post-expansion and post-treatment,to assess the changes of hard tissues and soft tissues.Results:Total treatment duration was 19 months.The posttreatment extraoral photographs show a correct middle line,The posttreatment intraoral photographs and dental casts show Class I canine and molar relationships on both sides,normal overjetand overbite,an a leveled Curve of Spee,satisfactory dental alignment and transverse relationships.No deviation of mandible,and photographs show general improvement in the facial profile.The function of TMJ was normal,and there was no high point of the occlusion.The function of mastication improved apparently.The analysis of model:The width of the middle part of upper arch in the pre-treatment post-expansion,post-treatment is 38 mm,46mm,40 mm respectively,the width of the base bone of maxilla in the pre-treatment post-expansion,post-treatment is45 mm,53mm,47 mm respectively,indicates the use of expansion improved the width of maxilla and dental arch effectively,without apparently buccal tipping of posterior teeth;and after the treatment the width of maxilla relapsed,which maybe due to the lack of retention time after expansion,but improvement on the width between pre-treatment and post-treatment still exits.(2)The length of the upper arch in the pre-treatment and post-expansion is 53 mm,52mm respectively,the length of the base bone of maxilla in the pre-treatment and post-expansion is 38.0mm,38.0mm respectively,indicates the use of expansion and maxillary protraction have on evident effect on the growth of maxilla.The length of the base bone of maxilla and mandible in the post-treatment is 35.9mm,39 mm,the former decreased apparently,maybe due to the mesial movement of upper molars,and the later increased apparently,maybe due to the distal movement of lower molars.The analysis of cephalometry:(1)In the pre-treatment U1-SN is 71.7°,U1-NA is 32.1°,in the post-expansion U1-SN is 71.7°,U1-NA is32.0°,which means the combination of rapid palatal expansion and maxillary protraction didn't cause evident skeletal changes on the sagittal or coronol direction;After the second phase of treatment,77.6° of SNA,79.0°of SNB,negative 1.4° of ANB,and negative 2.9mm of Wits appraisal shows the improvements of skeletal Class ? relationship;the increase of U6-Ptm indicates the obvious mesial movement of maxillary first molars,in the mean time,for the distance between the frontal border of ramus of mandible and the distal side of the lower second molars decreased,the lower molars moved to distal obviously with the use of early intermaxillary short class ? elastics which consist of low force.,the molar relationship of the case changed fromClass ? to Class I,resulting in a more favorable relationship.(2)The degree of FMA in the pre-treatment post-expansion,post-treatment was 27.0°,27.2° and28.1°respectively,The degree of SN-MP in the pre-treatment post-expansion,post-treatment was 35.0°,35.2° and 35.9°respectively,there was no apparent changes,which means the good control of vertical direction,the mandible just had a slight backward rotation as the SN to occlusal plane angle increased.The occlusal plane to Frankfort plane decreased in a large degree,so the occlusal plane rotate in a counter clockwise direction.Although a slight clockwise rotation of mandible happened,and both the anterior facial height and posterior facial height increased,it was still possible that the changes related to the development of mandible,because the distance of Co-Gn increased,and the vertical proportion between anterior facial height and posterior facial height was kept.The maxillary incisors were bucally tipped and protruded,and the mandibular incisors were lingually tipped and retruded.(3)The degree of nasiolabial angle in the pre-treatment and post-treatment was92.9°,85.4°respectively,the degree of Z angle in the pre-treatment and post-treatment was 80.0°,78.1°respectively,the distance of UL-EP in the pre-treatment and post-treatment was negative 4.1mm,negative 3.1mm respectively,the distance of LL-EP in the pre-treatment and post-treatment was negative 1.8mm,1.3mm respectively,indicates the improved and satisfied profile.Conclusion:In this report,by using the intermaxillary short class ? elastic early,the curve of Spee has been levelled,the upper and lower incisors tipped in a compensatory way for the correction of the anterior overbite and overjet.And the upper molars moved mesially,while the lower molars moved distally and erected obviously to get the Class I molar relationship.The upper molars and lower incisors extruded which results in the counter clockwised rotation of occlusal plane,and the long axis of the lower teeth were vertical to the occlusal plane.In a word,in this case the vertical and sagittal discrepancyhad been controlled effectively in the early stage by using the early intermaxillary short class ? elastic.