title: The timing of extraction of non-restorable first permanent molars: a systematic review.
abstract: OBJECTIVE
  To identify the ideal timing of first permanent molar extraction to reduce the future need for orthodontic treatment.
  
  
  METHODS
  A computerised database and subsequent manual search was performed using Medline database, Embase and Ovid, covering the period from January 1946 to February 2013. Two reviewers (JE and ME) extracted the data independently and evaluated if the studies matched the inclusion criteria. Inclusion criteria were specification of the follow-up with clinical examination or analysis of models, specification of the chronological age or dental developmental stage at the time of extraction, no treatment in between, classification of the treatment result into perfect, good, average and poor. The search was limited to human studies and no language limitations were set.
  
  
  RESULTS
  The search strategy resulted in 18 full-text articles, of which 6 met the inclusion criteria. By pooling the data from maxillary sites, good to perfect clinical outcome was estimated in 72% (95% confidence interval 63%-82%). Extractions at the age of 8-10.5 years tended to show better spontaneous clinical outcomes compared to the other age groups. By pooling the data from mandibular sites, extractions performed at the age of 8-10.5 and 10.5-11.5 years showed significantly superior spontaneous clinical outcome with a probability of 50% and 59% likelihood, respectively, to achieve good to perfect clinical result (p<0.05) compared to the other age groups (<8 years of age: 34%, >11.5 years of age: 44%).
  
  
  CONCLUSIONS
  Prevention of complications after first permanent molars extractions is an important issue. The overall success rate of spontaneous clinical outcome for maxillary extraction of first permanent molars was superior to mandibular extraction. Extractions of mandibular first permanent molars should be performed between 8 and 11.5 years of age in order to achieve a good spontaneous clinical outcome. For the extraction in the maxilla, no firm conclusions concerning the ideal extraction timing could be drawn.
authors.affiliation: Clinic for Orthodontics and Paediatric Dentistry, Center of Dental Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Eichenberger
authors.affiliation: Clinic for Orthodontics and Paediatric Dentistry, Center of Dental Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: J
authors.initials: J
authors.lastname: Erb
authors.affiliation: Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Zwahlen
authors.affiliation: Clinic for Orthodontics and Paediatric Dentistry, Center of Dental Medicine, University of Zurich, Zurich, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Schätzle
mesh_terms: D006801:Humans; D008334:Mandible / Q000601:surgery; D008437:Maxilla / Q000601:surgery; D008963:Molar / Q000601:surgery*; D013997:Time Factors; D014081:Tooth Extraction