title: Three-dimensional soft-tissue and hard-tissue changes in the treatment of bimaxillary protrusion.
abstract: BACKGROUND
  Facial convexity related to bimaxillary protrusion is prevalent in many populations. Underlying skeletal protrusion combined with increased dentoalveolar protrusion contributes to facial muscle imbalance and lip incompetence, which is undesirable for many patients. In this study, we evaluated the relationship between soft-tissue and hard-tissue changes in an orthodontically treated Asian population.
  
  
  METHODS
  Twenty-four consecutive adult Asian patients (mean age, 24 years), diagnosed with severe bimaxillary dentoalveolar protrusion, were evaluated using pretreatment and posttreatment cone-beam computed tomography. The patients were treated with 4 first premolar extractions followed by anterior retraction with either skeletal or intraoral anchorage. Serial cone-beam computed tomography radiographs were registered on the entire cranial base and fossa. Soft-tissue and hard-tissue changes were determined through landmark displacement and color mapping.
  
  
  RESULTS
  Upper lip retraction was concentrated between the nasolabial folds and commissures. Lower lip retraction was accompanied by significant redistribution of soft tissues at pogonion. Soft-tissue changes correlated well with regional facial muscle activity. Significant retractions (2-4 mm) of the soft tissues occurred beyond the midsagittal region. Use of skeletal anchorage resulted in 1.5 mm greater lower lip retraction than intraoral anchorage, with greater retraction of the maxillary and mandibular incisor root apices.
  
  
  CONCLUSIONS
  Profound soft-tissue changes accompanied retraction of the anterior dentition with both treatment modalities.
authors.affiliation: Orthodontic resident, Division of Orthodontics, Department of Orofacial Sciences, University of California-San Francisco, CA, USA. Richard.Solem@ucsf.edu
authors.forename: R Christian
authors.initials: RC
authors.lastname: Solem
authors.forename: Richard
authors.initials: R
authors.lastname: Marasco
authors.forename: Luis
authors.initials: L
authors.lastname: Guiterrez-Pulido
authors.forename: Ib
authors.initials: I
authors.lastname: Nielsen
authors.forename: Seong-Hun
authors.initials: SH
authors.lastname: Kim
authors.forename: Gerald
authors.initials: G
authors.lastname: Nelson
mesh_terms: D000328:Adult; D059925:Anatomic Landmarks / Q000473:pathology; D001213:Asian; D001641:Bicuspid / Q000601:surgery; D002508:Cephalometry / Q000379:methods*; D054893:Cone-Beam Computed Tomography / Q000379:methods; D005145:Face; D005147:Facial Bones / Q000473:pathology*; D005152:Facial Muscles / Q000473:pathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007180:Incisor / Q000473:pathology; D008046:Lip / Q000473:pathology; D008297:Male; D008311:Malocclusion, Angle Class I / Q000628:therapy*; D008334:Mandible / Q000473:pathology; D008437:Maxilla / Q000473:pathology; D009666:Nose / Q000473:pathology; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation / Q000379:methods; D016382:Orthodontic Appliance Design; D010159:Palate / Q000473:pathology; D019227:Tooth Apex / Q000473:pathology; D014081:Tooth Extraction; D014087:Tooth Movement Techniques / Q000295:instrumentation / Q000379:methods; D055815:Young Adult