Clinical Application Of The Rapid Maxillary Expansion With Face Mask Therapy On The Treatment Of Class Ⅲ Malocclusion In The Permanent Dentition Stage

Objective：The purpose of this study was to investigate clinical effect of treatmentof Class III malocclusion patients using rapid maxillary expander and protraction facemask in the permanent dentition stage.Methods：Case of adolescence male with Class III malocclusion was selected todental department of Dalian Friendship Hospital in2012. The patient was a14-year-oldmale，concave facial profile. Based on clinical examination,we can found that thepatient had slight maxillary deficiency and excess mandibular bone development,bilateral molar Class III relationship, the midline irregularity, anterior crossbite. X-rayanalysis showed: SNA:74°,SNB:76.3°,ANB:-2.3°, Wits:-12mm, ANS-Ptm:50mm,Yaxis:69.5°, FMA:31°. According to the result of clinical examination, we decided tocombine rapid maxillary expander with protraction face mask. By analysing thedifference between pretreatment and posttreatment cephalometric radiograph, model,and the oral occlusion, observing changes of soft tissue profile, we can evaluate theeffectiveness and stability of treatment.Results: Total treatment duration was21months. By adopting rapid maxillary expansion during upgrowth, the mid-palatal suture could be opened remarkably, theupper dental arch width and length could be increased, the growth and development ofmaxillary can also be stimulated. At the same time, combined fixed appliance withprotraction face mask,the lower jaw can rotate downward,the dentition can be alignedand leveled, the relationship of bilateral molar and overbite,overjet of anterior teeth canalso be improved. By analysing the difference between pretreatment and posttreatmentcephalometric radiograph, we can found SNA increase3.8°, SNB increase0.7°, ANBincrease3.1°,Wits increase4mm, ANS-Ptm increase3mm.Conclusion: In this case, by adopting rapid maxillary expansion with protractionface mask and fixed appliance,the patient has achieved great effect. The best effect ofthe treatment includes promoting maxillary growth that the same time establishing agood overbite,overjet and improving both molar relationship and masticatory function.