title: Short-term treatment effects produced by the Twin-block appliance: a systematic review and meta-analysis.
abstract: OBJECTIVE
  To evaluate dental, skeletal, and soft tissue effects during Twin-block treatment.
  
  
  METHODS
  A systematic search of several electronic databases (Medline, PubMed, Embase, all EBM reviews, and Web of Science) was conducted until July 2013, as well as a limited grey-literature search (Google Scholar). Human cephalometric studies that used a Twin-block appliance in a non-extraction and non-surgical approach were selected. A comparable control group of untreated subjects was required. Two authors independently reviewed and extracted data from the selected studies. Risk of bias was assessed. The type of meta-analysis was selected based on heterogeneity.
  
  
  RESULTS
  Ultimately 10 articles were included. Proclination of lower incisors, retroclination of upper incisors, distal movement of upper molars and/or mesial movement of lower molars, increase in mandibular length, and/or forward movement of the mandible were consistently reported. Clinically significant restraint of maxillary growth was not found. Although the mandibular body length is increased, the facial impact of it is reduced by the simultaneous increment of the face height. Changes of lower face height and occlusal plane inclination varied, suggesting that vertical dimension can be manipulated in patients who would benefit from lower molar extrusion. As for lip position, there is not enough evidence to suggest clear lip position changes.
  
  
  CONCLUSIONS
  Changes associated with a Class II correction were identified. Most of the changes individually were of limited clinical significance, but when combined reached clinical importance. No long-term changes were available.
authors: *Private Practice in Vancouver, British Columbia, Canada.
authors: Sayeh
authors: S
authors: Ehsani
authors: **Private Practice in Edmonton, Alberta, Canada.
authors: Brian
authors: B
authors: Nebbe
authors: ***Faculty of Dentistry, University of Para, Belem, Brazil.
authors: David
authors: D
authors: Normando
authors: ****Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada.
authors: Manuel O
authors: MO
authors: Lagravere
authors: ****Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada cf1@ualberta.ca.
authors: Carlos
authors: C
authors: Flores-Mir
mesh_terms: D002508:Cephalometry / Q000379:methods; D003766:Dental Occlusion; D005145:Face / Q000473:pathology; D006801:Humans; D007180:Incisor / Q000503:physiopathology; D008312:Malocclusion, Angle Class II / Q000628:therapy*; D008334:Mandible / Q000254:growth & development; D008437:Maxilla / Q000254:growth & development; D008963:Molar / Q000503:physiopathology; D016382:Orthodontic Appliance Design; D017289:Orthodontic Appliances, Functional; D014716:Vertical Dimension