title: Dental anomaly pattern (DAP): agenesis of mandibular second premolar, distal angulation of its antimere and delayed tooth formation.
abstract: OBJECTIVE
  To test the null hypotheses that children with unilateral agenesis of the mandibular second premolar (MnP2) do not show (1) greater distal angulation of the unerupted antimere and (2) delayed tooth formation compared with children without agenesis.
  
  
  METHODS
  Panoramic radiographs of 38 patients with unilateral aplasia of MnP2 were retrospectively examined and compared to a non-agenesic control group of 82 patients. Ages ranged from 8 to 15 years. Contralateral mandibular deciduous second molars were present for all participants. Each unerupted MnP2 was traced, and its developmental stage and angulation were recorded (measured with the distal angle and the premolar-molar angle). Dental age was evaluated using the Haavikko method. Student's t-test was performed to identify significant differences between the compared groups. The significance level for statistical testing was set at P < .05.
  
  
  RESULTS
  The results indicated a 9.5° decrease in the distal angle and a 13.2° increase in the premolar-molar angle for the unerupted MnP2 in the agenesis sample. This was a highly statistically significant difference (P < .001 and P < .0001, respectively) compared with the MnP2 inclinations in the control sample. The delay in dental age was significantly greater in patients with agenesis (2.1 years) compared with the delay in the control group (1.5 years) (P < .001).
  
  
  CONCLUSIONS
  Both null hypotheses are rejected. The results of this study statistically support the hypothesis that aplasia of MnP2, distally displaced MnP2s, and delayed tooth formation are part of a genetically related pattern of dental anomalies.
authors.affiliation: a  Graduate student, Department of Orthodontics, Hospital Sant Joan de Déu, University of Barcelona, Barcelona, Spain.
authors.forename: Joana
authors.initials: J
authors.lastname: Navarro
authors.forename: Maria
authors.initials: M
authors.lastname: Cavaller
authors.forename: Estela
authors.initials: E
authors.lastname: Luque
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Tobella
authors.forename: Alejandro
authors.initials: A
authors.lastname: Rivera
mesh_terms: D000293:Adolescent; D000366:Age Determination by Teeth; D000848:Anodontia / Q000150:complications*; D001641:Bicuspid / Q000002:abnormalities* / Q000000981:diagnostic imaging; D002648:Child; D005500:Follow-Up Studies; D006801:Humans; D008310:Malocclusion / Q000150:complications* / Q000000981:diagnostic imaging; D008334:Mandible / Q000000981:diagnostic imaging*; D008963:Molar / Q000000981:diagnostic imaging; D009805:Odontogenesis / Q000502:physiology*; D009811:Odontometry / Q000379:methods; D011862:Radiography, Panoramic; D012189:Retrospective Studies; D014094:Tooth, Deciduous / Q000000981:diagnostic imaging; D014097:Tooth, Unerupted / Q000000981:diagnostic imaging