title: Mandibular lip bumper treatment and second molar eruption disturbances.
abstract: BACKGROUND
  Mandibular lip-bumper (LB) nonextraction treatment, usually started before complete second molar (M2) eruption, inevitably interacts with the development of the dentition. Yet, its effects on M2 eruption are still unknown. The first aim of this study was to retrospectively investigate whether LB therapy (260 patients) enhances the risk for M2 ectopic eruptions and impactions in comparison with 135 untreated subjects. The second aim was to assess, among treated patients (n = 197), the main potential determinants of M2 impaction and ectopic eruption.
  
  
  METHODS
  M2 eruption and impaction were determined on panoramic radiographs. To assess the predictive role of M2 inclination in relation to the first molar, a panoramic radiograph suitable for this measurement before treatment was required. The data were analyzed by using software (version 8.2, SAS, Cary, NC).
  
  
  RESULTS
  LB treatment significantly enhanced M2 impaction and ectopic eruption. Negative prognostic factors were found. An initial inclination of the M2 greater than 30° was significantly associated with a higher impaction risk compared with an angulation less than 10°. LB treatment duration longer than 2 years increased the risk of ectopic eruptions.
  
  
  CONCLUSIONS
  While gaining space in the anterior arch, unwanted effects might be produced in the posterior arch. To be informed about these unplanned events is necessary to better optimize treatment.
authors.affiliation: Free Practitioner in Orthodontics, Naples, Italy. ferrofabrizia@libero.it
authors.forename: Fabrizia
authors.initials: F
authors.lastname: Ferro
authors.forename: Gloria
authors.initials: G
authors.lastname: Funiciello
authors.forename: Letizia
authors.initials: L
authors.lastname: Perillo
authors.forename: Paolo
authors.initials: P
authors.lastname: Chiodini
mesh_terms: D000293:Adolescent; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D005544:Forecasting; D006801:Humans; D008297:Male; D008310:Malocclusion / Q000000981:diagnostic imaging / Q000628:therapy; D008334:Mandible / Q000000981:diagnostic imaging; D008963:Molar / Q000000981:diagnostic imaging / Q000473:pathology*; D016382:Orthodontic Appliance Design; D009967:Orthodontic Appliances; D011862:Radiography, Panoramic; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors; D014079:Tooth Eruption, Ectopic / Q000000981:diagnostic imaging / Q000209:etiology*; D014087:Tooth Movement Techniques / Q000295:instrumentation*; D014095:Tooth, Impacted / Q000000981:diagnostic imaging / Q000209:etiology*