title: The mandibular permanent second molars and their risk of impaction: a retrospective study.
abstract: OBJECTIVE
  The aim of this retrospective study is promote a better understanding of the impaction of teeth 37 and 47 by means of clinical and statistical data from the point of view of early interceptive treatment.
  
  
  METHODS
  
  
  
  METHODS
  478 patients of the Orthodontic School of "La Sapienza" University of Rome (Italy) were studied to assess the eruption of teeth 37 and 47 on at least two good-quality panorex using angular measurements and Nolla's index from January 2008 to December 2013. Data were analysed using ANOVA and Tukey HSD test (P < 0.05).
  
  
  RESULTS
  The data obtained on the possible correlations between the examined teeth and the four reference angles show that at t0, the angular variation of teeth 36 or 46 is constant when the teeth are at the end of their eruptive process, while for teeth 37 and 47, this variation is always constant. At t0, the first and the second molars of both quadrants, during eruption showed a similar behaviour. At t1, the four teeth examined in the patients sample showed a model of development analogous to that exhibited at t0.
  
  
  METHODS
  a constant variation (t0-t1) is present among the differences in the development of the 36 and the two angular values, while difference in development of the 37 and that of the angular value is constant only in relationship to the difference in development of the mandibular first molar of the same quadrant. The variations between the difference in development of the 47 and in angular value (t0-t1) are constant only when related to the developing 46. The analytic variance of gradience (vargrad) data confirm peculiar behaviour of the first one, according to both mandibular molars, during their eruptive development.
  
  
  CONCLUSIONS
  Adoption of universally recognised radiographic predictive methods allows assessment of the case and allows the specialist to plan a suitable treatment to prevent or intercept the molar impaction, with a perspective of a less invasive and shorter therapy. Although rare, impaction of teeth 37 and 47 often requires a complex, multidisciplinary approach.
authors.affiliation: Student, Orthodontic School of Specialisation, Department of Oral and Maxillofacial Sciences, "Sapienza" University of Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Alligri
authors.affiliation: Student, Orthodontic School of Specialisation, Department of Oral and Maxillofacial Sciences, "Sapienza" University of Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Putrino
authors.affiliation: Researcher, Department of Oral and Maxillofacial Sciences, "Sapienza" University of Rome, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Cassetta
authors.affiliation: Associate Professor, School of Dentistry, Department of Oral and Maxillofacial Sciences, "Sapienza" University of Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Silvestri
authors.affiliation: Full Professor, Head, School of Dentistry, Department of Oral and Maxillofacial Sciences, "Sapienza" University of Rome, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Barbato
authors.affiliation: Associate Professor, Director of the Orthodontic School of Specialization, School of Dentistry, Department of Oral and Maxillofacial Sciences, "Sapienza" University of Rome, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Galluccio
mesh_terms: D000293:Adolescent; D000328:Adult; D006801:Humans; D008334:Mandible; D008963:Molar / Q000000981:diagnostic imaging*; D011862:Radiography, Panoramic; D012189:Retrospective Studies; D014095:Tooth, Impacted / Q000000981:diagnostic imaging*; D055815:Young Adult