title: Quad-helix appliances may be more successful than removable expansion plates at correcting posterior crossbites.
abstract: METHODS
  The Cochrane Oral Health Group's Trials Register, the Cochrane Central Register of Controlled Trials (CENTRAL) Medline, Embase, the US National Institutes of Health Trials Register and the World Health Organisation (WHO) Clinical Trials Registry Platform were searched with no restrictions.
  
  
  METHODS
  Randomised controlled trials (RCTs) of orthodontic treatment for posterior crossbites in children and adults were considered.
  
  
  METHODS
  Study selection, data abstraction and risk of bias assessment were carried out independently by two reviewers. Dichotomous data were summarised with risk ratios (RR) and 95% confidence intervals (CIs) and continuous data with mean differences (MD) with 95% CIs. Meta-analyses were conducted when comparisons and outcomes were sufficiently similar.
  
  
  RESULTS
  Fifteen studies were included; seven were at high risk of bias, two at low risk and six at unclear risk. Nine studies compared fixed appliances with mid-palatal expansion but no difference between appliances was reported. Low quality evidence from two studies with 96 participants found that fixed quad-helix appliances may be 20% more likely to correct crossbites than removable expansion plates (RR 1.20; 95% CI 1.04 to 1.37), and quad-helix appliances may achieve 1.15 mm more molar expansion than expansion plates (MD 1.15 mm; 95% CI 0.40 to 1.90;). Very limited evidence showed that both fixed quad-helix appliances and removable expansion plates were superior to composite onlays in terms of crossbite correction, molar and canine expansion.
  
  
  CONCLUSIONS
  There is a very small body of low to moderate quality evidence to suggest that the quad-helix appliance may be more successful than removable expansion plates at correcting posterior crossbites and expanding the inter-molar width for children with early mixed dentition (aged eight to 10 years). The remaining evidence we found was of very low quality and was insufficient to allow the conclusion that any one intervention is better than another for any of the outcomes in this review.
authors.affiliation: Kettering General Hospital NHS Foundation Trust, Kettering, Northamptonshire, UK.
authors.forename: Julian
authors.initials: J
authors.lastname: O'Neill
mesh_terms: D006801:Humans; D009971:Orthodontics, Corrective / Q000379:methods*; D057887:Overbite / Q000628:therapy*