Three case-control studies were included in the review, one prospective and two retrospective (number of participants not stated).
None of the studies were blinded or analysed by intention-to- treat. Only one study was prospective, two had no long-term follow-up, and overall they fulfilled only 45 to 55% of the 20 quality criteria assessed.
There were statistically significant changes in the intervention group for the following outcomes:
the anteroposterior length of the mandible (mandibular protrusion: 2 studies, increase 1.2 to 2.9 degrees; mandibular dimensions: 3 studies, increase 0.7 to 2.7 mm);
the vertical height of the ramus;
the lower facial height (change in vertical dimensions for posterior and lower anterior facial heights: 1.4 to 2.5 mm and 1.2 to 3 mm, respectively; 2 studies of each);
mandibular incisor proclination;
mesial movement of the lower molars; and
distal movement of the upper molars.
Post-treatment relapse in the overjet and molar relationships was observed.