title: An active, skeletally anchored transpalatal appliance for derotation, distalization and vertical control of maxillary first molars.
abstract: OBJECTIVE
  The objective of this investigation was to evaluate treatment outcomes of the skeletally anchored 'Frog' appliance.
  
  
  METHODS
  A single-centre, retrospective study was performed.
  
  
  METHODS
  Private orthodontic practice.
  
  
  METHODS
  Patients who had undergone comprehensive orthodontic treatment with the skeletally anchored 'Frog' appliance.
  
  
  METHODS
  43 participants (20 males and 23 females) who had received treatment with the skeletally anchored 'Frog' appliance where included. In order to explore dentoalveolar and skeletal treatment outcomes, pre- (T1) and post- (T2) treatment measurements were performed on patients' plaster models and cephalometric images. Comparisons between T1 and T2 were made by means of a Student's t-test. All statistical analyses were conducted at the 0·05 level of statistical significance.
  
  
  RESULTS
  Study model analysis revealed a statistically significant derotation of maxillary molars (μΔT2-T1=9·5°, P<0·001) as well as an increase in transverse arch dimensions at the end of treatment (μΔT2-T1=2·2 mm, P<0·001). Cephalometric changes included bodily distalization of maxillary molars (μΔ(T2-T1)=-1·9 mm, P<0·001), as well as noticeable angular displacement (μΔT2-T1=4·1°, P=0·004). No significant anchorage loss was observed, as displayed by the limited change in maxillary incisor position (μΔ(T1-T2)=0·2 mm, P=0·45). In addition, excellent vertical control of the maxillary molars was achieved, with no change in the mandibular plane (ML/NSL) angle (μΔT2-T1=0·3°, P=0·38).
  
  
  CONCLUSIONS
  The skeletal 'Frog' is effective in derotating and distalizing maxillary molars without anchorage loss and with excellent vertical control.
authors.affiliation: Private Practice, Reinheim, Germany; Department of Orthodontics, University of Heidelberg, Germany.
authors.forename: Jan
authors.initials: J
authors.lastname: Hourfar
authors.affiliation: Private practice Traben-Trarbach, Germany; Department of Orthodontics, University of Homburg/Saar, Germany.
authors.forename: Björn
authors.initials: B
authors.lastname: Ludwig
authors.affiliation: Department of Orthodontics and Dentofacial Orthopedics, Tufts University School of Dental Medicine, Boston, MA, USA.
authors.forename: Georgios
authors.initials: G
authors.lastname: Kanavakis
mesh_terms: D002508:Cephalometry / Q000379:methods; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008334:Mandible / Q000473:pathology; D008437:Maxilla / Q000473:pathology; D003765:Models, Dental; D008963:Molar / Q000473:pathology*; D052280:Orthodontic Anchorage Procedures / Q000295:instrumentation* / Q000379:methods; D016382:Orthodontic Appliance Design; D012189:Retrospective Studies; D012399:Rotation; D014087:Tooth Movement Techniques / Q000295:instrumentation* / Q000379:methods; D016896:Treatment Outcome
keywords: Class II correction; molar derotation; molar distalization; skeletal anchorage; vertical control