title: Correlation between the frequency of eruption disorders for first permanent molars and the occurrence of malocclusions in early mixed dentition.
abstract: OBJECTIVE
  We analyzed the incidence of eruption disorders in 6-year molars during the first phase of mixed dentition, and then determined the risks for later dental arch development according to specific combinations of orthodontic malocclusions. We, thus, aimed to derive potential conclusions for preventative orthodontics.
  
  
  METHODS
  In this cross-sectional study, 8,041 kindergarten and school children with early mixed dentition were randomly selected and clinically examined. Examinations were performed in two consecutive years during the standard dental screening that school children undergo. The average age was 6.9 years. We defined an eruption of the 6-year molars as being disturbed when (1) the distal cusps had erupted further than the mesial cusps, (2) the mesial inclination of the occlusal surface revealed disturbed eruption, and (3) the 6-year molar had erupted below the second primary molar.
  
  
  RESULTS
  Disturbed eruption of the first permanent molars was observed in 102 of these children. The upper 6-year molars were affected more often (88.5%) than the lower molars. Bilateral disturbed eruption of the upper molars was the most frequent combination of symptoms found. Although disturbed eruption was diagnosed most often in 6- and 7-year-old children, the 8-year-old children presented 20% of the eruption disorders. Moreover, 72.6% of the children with disturbed eruption presented at least one additional orthodontic malocclusion. Crowding (p ≤ 0.001), lateral malocclusions (p ≤ 0.001), and mandibular prognathism (p = 0.009) were present significantly more often in children with disturbed eruption of 6-year molars.
  
  
  CONCLUSIONS
  Delayed eruption and false direction of eruption of the upper 6-year molars may-already at an early stage-raise the likelihood of problems during later dental arch development, such as crowding in the sagittal and transverse directions or Class III developments.
authors: Department of Orthodontics, School of Dentistry "Hans Moral", University of Rostock, Germany. anja.salbach@uni-rostock.de
authors: Anja
authors: A
authors: Salbach
authors: Britt
authors: B
authors: Schremmer
authors: Rosemarie
authors: R
authors: Grabowski
authors: Franka
authors: F
authors: Stahl de Castrillon
mesh_terms: D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D003724:Dental Arch; D003818:Dentition, Mixed; D019229:Dentition, Permanent; D005260:Female; D005858:Germany; D006801:Humans; D008297:Male; D008310:Malocclusion / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology*; D008403:Mass Screening; D008963:Molar; D009971:Orthodontics, Corrective; D013223:Statistics as Topic; D014079:Tooth Eruption, Ectopic / Q000175:diagnosis / Q000453:epidemiology*