title: Failure rates and survival analysis of maxillary expansion appliances: a 24-year retrospective analysis.
abstract: OBJECTIVE
  The purpose of this study was to describe the failure rates of maxillary expansion appliances (MEAs) and assess risk variables associated with failures and treatment time.
  
  
  METHODS
  Retrospective chart reviews were performed on 436 primary or mixed dentition patients presenting with crossbite to a private practice between 1981-2005. Survival analysis was used to analyze and compare the types of MEAs with respect to the treatment time. The effect of demographic and clinical characteristics on appliance failure and treatment time was assessed using linear and logistic regression models.
  
  
  RESULTS
  The average age at insertion of a MEA was 8 years, 4 months (+/-1.72 SD). Nineteen percent (n=84) of the MEAs failed, with a median treatment time for all appliances of 216 days (interquartile range=126 days). Cement loss (69%) was the most common type of failure. The likelihood of an appliance failing increased in children with a malocclusion other than Class I (adjusted odds ratio=1.91; 95% CI=1.16-3.14) and was nearly 4 times greater when a quad helix was used compare to the Haas appliance (adjusted odds ratio=3.60; 95% CI=1.92-6.75). The treatment time was significantly affected by the type of crossbite present and the occurrence of an appliance failure (P=.001).
  
  
  CONCLUSIONS
  The use of a quad helix appliance and the presence of malocclusion other than Class I was significantly predictive of appliance failure. Treatment time was increased when MEAs failed and bilateral crossbite was present.
authors.affiliation: University of Maryland, Baltimore, Md, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Beebe
authors.forename: Rocio B
authors.initials: RB
authors.lastname: Quinonez
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Shick
authors.forename: Se Hee
authors.initials: SH
authors.lastname: Kim
authors.forename: David B
authors.initials: DB
authors.lastname: Kennedy
mesh_terms: D002484:Cementation; D002648:Child; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008310:Malocclusion / Q000145:classification / Q000628:therapy*; D016382:Orthodontic Appliance Design; D009967:Orthodontic Appliances / Q000145:classification*; D010155:Palatal Expansion Technique / Q000295:instrumentation*; D012189:Retrospective Studies; D016019:Survival Analysis; D017211:Treatment Failure