title: Occlusal morphology of mandibular second molars in Iranian adolescents.
abstract: BACKGROUND
  During human evolution, the morphology of mandibular molar occlusal surface has changed from pattern "y" to pattern "+". Six types of occlusal patterns were classified as: +4, 4-y,+5, 5-y,+6 and 6-y.
  
  
  OBJECTIVE
  To determine the prevalence of these six types of mandibular second molars in Iranian adolescents.
  
  
  METHODS
  This descriptive investigation was undertaken in the high schools of Isfahan city, Iran. The students were selected by cluster sampling method, and then they were screened and only those with erupted mandibular second molars bilaterally were selected.
  
  
  METHODS
  A total of 794 cases were randomly selected and the number of cusps and groove pattern of mandibular second molar were examined intra-orally and by studying dental casts.
  
  
  METHODS
  Descriptive statistics and chi-square test were used for data analysis.
  
  
  RESULTS
  The most frequent occlusal configuration was the "+4" form (76.9%). A total of 683 cases (86%) were found to have four-cusp form, 104 cases (13.1%) were five-cusp form and 7 cases (0.9%) were six-cusp form.
  
  
  CONCLUSIONS
  The most frequent occlusal configuration was the "+4" form; thus, there is a high evolutionary trend in Iranian mandibular second molars.
authors.affiliation: Department of Prosthodontics, Isjahan University of Medical Sciences, Hezar-Jalib, Ave Isjahan, Iran.
authors.forename: Ramin
authors.initials: R
authors.lastname: Mosharraf
authors.forename: Behnaz
authors.initials: B
authors.lastname: Ebadian
authors.forename: Zeilabi
authors.initials: Z
authors.lastname: Ali
authors.forename: Akhlaghi
authors.initials: A
authors.lastname: Najme
authors.forename: Shamashian
authors.initials: S
authors.lastname: Niloofar
authors.forename: Karimi
authors.initials: K
authors.lastname: Leila
mesh_terms: D000293:Adolescent; D016009:Chi-Square Distribution; D003766:Dental Occlusion; D005260:Female; D006801:Humans; D007492:Iran; D008297:Male; D008334:Mandible; D008963:Molar / Q000033:anatomy & histology*; D009811:Odontometry; D012494:Sampling Studies; D018709:Statistics, Nonparametric; D019228:Tooth Crown / Q000033:anatomy & histology*