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 (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.