title: Birth order--a risk factor for dental trauma?
abstract: BACKGROUND
  Many character traits are influenced by birth order with greatest differences between first and lastborns.
  
  
  OBJECTIVE
  To investigate the influence of birth order on the risk of dental trauma.
  
  
  METHODS
  Five hundred mothers in Switzerland were interviewed personally regarding dental trauma in their children. Inclusion criteria were a family size of at least two children. Data of 1282 children were collected.
  
  
  RESULTS
  Thirty-two percent of the children had sustained one or more dental trauma before the age of 16 (57% male, 43% female). In children who had sustained dental trauma twice, the gender ratio moved to 68% male and 32% female (P = 0.003). Regarding birth order, lastborns sustained more second dental traumas. Relative risk of second dental trauma was 2.1 times higher in lastborns than in firstborns (P = 0.02). Moreover, certain character traits in children are influenced by birth order. According to their mothers, lastborns were more curious, less calm and less deliberate than firstborns (P < 0.001). Second born without younger siblings were more athletic/active than firstborns (P = 0.011). Athletic/active children as well as not calm/deliberate children sustained second dental trauma more often than not athletic/active (P = 0.038) and calm/deliberate children (P < 0.001).
  
  
  CONCLUSIONS
  Birth order is a risk factor for sustaining dental trauma twice. Character traits of lastborns (curious, not calm/deliberate and aggressive) could be reasons for higher risk of dental trauma.
authors.affiliation: Department of Oral Surgery, Oral Radiology and Oral Medicine, Centre of Dental Traumatology, University of Basel, Basel, Switzerland.
authors.forename: Matthias
authors.initials: M
authors.lastname: Käch
authors.forename: Gabriel
authors.initials: G
authors.lastname: Krastl
authors.forename: Nicola U
authors.initials: NU
authors.lastname: Zitzmann
authors.forename: Sebastian
authors.initials: S
authors.lastname: Kühl
authors.forename: Andreas
authors.initials: A
authors.lastname: Filippi
mesh_terms: D000293:Adolescent; D001722:Birth Order; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007407:Interviews as Topic; D008297:Male; D012307:Risk Factors; D013557:Switzerland; D018677:Tooth Injuries / Q000453:epidemiology*
keywords: birth order; characteristics; dental trauma; firstborn; lastborn