Since the 1930s many orthodontists, mainly in Germany, believed to control the growth of the jaws by removable orthodontic appliances. Especially with functional appliances like Activator, Bionator or Twin Block the lower jaw should be increased or decreased in length. These appliances were used particularly for correction of mandibular retrognathism. Until now functional treatment is supported by many orthodontists.
The question is whether common appliances like Activators are really suitable for mandibular growth stimulation. The authors of a recent systematic review have therefore collected data from the whole orthodontic literature of the last decades. 17 studies of removable functional appliances (RFAs) were included. The patients’ mean age was 10,6 years. The authors found disappointing minimal effects of RFAs on facial growth. Treatment was associated with minimal reduction of SNA angle (MD = −0.28 degree/year) and minimal increase of SNB angle (MD = 0.62 degree/year.
Regarding the relation between upper and lower jaw a moderate decrease of ANB angle (MD = -1.14 degree/year) was shown. The magnitude of their effects on facial growth is well below a level that would be noticeable – therefore clinically irrelevant. However, all studies proved that RFA treatment resulted in significant dentoalveolar changes. The effects of RFAs on skeletal growth were measured immediately after therapy and were undetecable some years later. The authors conclude that RFAs are effective for treatment of mandibular retrusion, but their effects are mainly restricted to tooth movement, treatment effects are mainly dentoalveolar rather than skeletal.
Reference: Koretsi V, Zymperdikas VF, Papageorgiou SN, Papadopoulos MA. Treatment effects of removable functional appliances in patients with Class II malocclusion: a systematic review and meta-analysis. Eur J Orthod. 2015 Aug;37(4):418-34. doi: 10.1093/ejo/cju071. Review. PubMed PMID: 25398303