title: Actuarial life-table analysis of lower impacted wisdom teeth in general dental practice.
abstract: BACKGROUND
  The appropriateness of extraction of asymptomatic impacted third molars has been much debated and as a result the number of extractions has fallen in the UK in the past few years. As a direct consequence of this decrease more impacted third molars are left in situ and yet, little is known about the natural history of these teeth.
  
  
  OBJECTIVE
  The aim of this study was to create an actuarial life-table and related survival analysis that would shed light on the natural history of an impacted lower third molar.
  
  
  METHODS
  Panoramic radiographs taken in 14 different general dental practices in Scotland were analysed and matched with their respective case notes in order to generate a sample of patients with asymptomatic impacted lower third molars. Subjects were assessed to confirm the presence of impaction and absence of symptoms and then re-assessed 1 year later for the development of symptoms during the study period to relate the incidence of symptoms within 1 year in the sample studied to age. Logistic regression was used to construct a life table based on the survival of symptom-free teeth (independently of extraction) during the study period.
  
  
  RESULTS
  The number of patients included in the study was 583 and 421 for the baseline and follow-up assessments respectively. The total number of teeth analysed in both appointments was 676; from those 37 (5.47%) were extracted during the study period. About 562 teeth (83.13%) survived the study period symptom-free. There was a statistically significant inverse association between the development of symptoms studied and age. There was no statistically significant association between extraction and age.
  
  
  CONCLUSIONS
  The study indicates that older patients are less likely to develop the symptoms studied. In addition the authors believe that there is evidence to suggest that general dental practitioners might not be following current guidelines when deciding whether or not to extract an impacted lower third molar in the centres studied.
authors.affiliation: General Dental Practitioner, Aberdeen, Scotland, UK. mfernandes10@hotmail.com
authors.forename: Marcelo José
authors.initials: MJ
authors.lastname: Fernandes
authors.forename: Graham Richard
authors.initials: GR
authors.lastname: Ogden
authors.forename: Nigel Berry
authors.initials: NB
authors.lastname: Pitts
authors.forename: Simon Alexander
authors.initials: SA
authors.lastname: Ogston
authors.forename: Danny Adolph
authors.initials: DA
authors.lastname: Ruta
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D005792:General Practice, Dental; D006801:Humans; D015993:Life Tables; D016015:Logistic Models; D008297:Male; D008334:Mandible; D008875:Middle Aged; D008964:Molar, Third / Q000473:pathology*; D010497:Pericoronitis / Q000453:epidemiology; D011862:Radiography, Panoramic; D012606:Scotland / Q000453:epidemiology; D016019:Survival Analysis; D014081:Tooth Extraction / Q000706:statistics & numerical data; D014095:Tooth, Impacted / Q000453:epidemiology*; D014098:Toothache / Q000453:epidemiology; D055815:Young Adult