An active, skeletally anchored transpalatal appliance for derotation, distalization and vertical control of maxillary first molars.

OBJECTIVE: The objective of this investigation was to evaluate treatment outcomes of the skeletally anchored 'Frog' appliance. DESIGN: A single-centre, retrospective study was performed. SETTING: Private orthodontic practice. PARTICIPANTS: 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 (muDeltaT2-T1=9.5 degrees , P<0.001) as well as an increase in transverse arch dimensions at the end of treatment (muDeltaT2-T1=2.2 mm, P<0.001). Cephalometric changes included bodily distalization of maxillary molars (muDelta(T2-T1)=-1.9 mm, P<0.001), as well as noticeable angular displacement (muDeltaT2-T1=4.1 degrees , P=0.004). No significant anchorage loss was observed, as displayed by the limited change in maxillary incisor position (muDelta(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 (muDeltaT2-T1=0.3 degrees , P=0.38). CONCLUSIONS: The skeletal 'Frog' is effective in derotating and distalizing maxillary molars without anchorage loss and with excellent vertical control.