Growth Modification Treatment Of Skeletal Class Ⅲ Malocclusion

Objective: The purpose of this research is to evaluate Curative effect of growthmodification treatment of skeletal class Ⅲ malocclusion with maxillary expander andprotraction face mask.Methods: A12year old male with skeletal class Ⅲ malocclusion patient wasselected as the object. After analyzed by the modified analysis of cervical vertebra, thepatient was in the CVS3stage. The patient was in the early stage of permanent dentitionwith a retrusive maxilla and a normal mandible. The maxillary and mandibular thirdpermanent molars and maxillary second permanent molars were not erupted. Leftmaxillary canine was erupting. Anterior incisors were cross bite. The both sides molarwas in the Class Ⅲ relationship. Maxillary arch crowding is3.0mm and mandibulararch diastema is3.5mm. The median line of upper dentition was correct, themandibular dental midline deviated1-1.5mm to the left relative to the facial midline.The patient, without skeletal class Ⅲ malocclusion family history, has a retrusive upperlip and a concave facial profile. The patient was treated by2-phase continuous treatment.The first phase of treatment began with maxillary expander and protraction face masktherapy, the aim was to correct the skeletal class Ⅲ relationship by promoting thegrowth of maxialla. Enhancement of the facial profile and achievement of positive overjet and overbite was obtained at the end of this phase. After this phase, Straight ArchWire Technique treatment was started. The goals of this phase of treatment were tobring the teeth into alignment and correct vertical discrepancies by leveling out the arch.Furthermore, after closing residual spaces in the arches and correcting molarrelationships, normal occlusion in the anteroposterior plane of dentition was obtained.The lateral cephalometric radiographs of pre-treatment and post-treatment in differentphase were traced. The maxillary growth and movement was measured to evaluate thefacial changes caused by the modification of maxilla. At the same time, the influence of maxillary expander and protraction face mask on the maxillary dentition was observedby measuring the movement of the upper molars and incisors. To evaluate the curativeeffect of maxillary expander, arch width was measured in the pre-treatment and posttreatment cast models.Results: The course of orthodontical treatment lasted25months. After treatment,the patient’s teeth were brought into alignment and archs were leveled out. The patienthas neutral molar relationship, stable occlusion and normal overbite and overjet. Themedian lines of both dental arches were not deviated relative to the facial midline. Thepatient satisfied with the overall outcome.1, Sagittal changes of hard tissue: SNA andPtm-s raised, point A moved forward2.0mm, indicating the maxilla moved forward.Both the numerical value of ANS-Ptm and the length of maxillary dental arch increasedby2.5mm, indicating that the significant growth of the maxilla. The numerical value ofANB increased from-2.0to3.5, the numerical value of Wits increased from-10.0to-4.0, indicating that the skeletal class Ⅲ relationship changed into skeletal class Irelationship. The numerical value of UIE-Y and UIA-Y respectively increased7.0mmand6.0mm, the numerical value of UM1E-Y and UM1A-Y respectively raised5.0mmand4.5mm, indicating that the maxillary molars and incisors moved forward in theprocess of forward movement of maxilla.2, Vertical changes of hard tissue: thenumerical value of ANS-Me increased, the increased lower facial height made thepercentage of face more proportional. The maxillary first molar extracted6mm and thenumerical value of MP-SN increased2°, indicating that the clockwise rotation ofmandible was occurred.3, Changes of soft tissue: The concave facial profile of thepatient was corrected. The patient’s facial profile was enhanced by the more protrusiveupper lip and more retrusive lower lip.Conclusions: The growth modification treatment, with maxillary expander andprotraction face mask, can significantly promote the growth of maxilla and correctskeletal class Ⅲ malocclusion. Maxillary expander and protraction face mask therapy isan effective treatment method, which is especially suit for the skeletal class Ⅲmalocclusion with retrusive maxilla.