title: Differences in various measurements on panoramic radiograph among erupted and impacted lower third molar groups.
abstract: OBJECTIVE
  To determine the differences in various linear and angular measurements between erupted and impacted lower third molar group on conventional panoramic radiographs.
  
  
  METHODS
  The quasi-experimental study based on non-probability convenience sampling and done at the National Institute of Oral Diseases, Karachi, comprised 140 patients having full dentition with bilaterally present mandibular third molars varying between ages of 18-30 years. After clinical examination, 280 lower third molars were divided into two groups; Group A had erupted, while Group B comprised impacted mandibular third molars. All radiographs were traced and measured for five variables to compare the two groups. For statistical purpose, SPSS version 10, and t test were used.
  
  
  RESULTS
  Retromolar space measured from Xi (centre of ramus) was 31.60 +/- 3.33 mm in Group A and 27.02 +/- 4.17mm in Group B. Retromolar space measured from anterior edge of ramus (AER) was 16.30 +/- 2.51 mm in Group A and 11.21 +/- 3.69 in Group B. Mesiodistal width was 13.39 +/- 1.44mm in Group A and 13.80 +/- 1.58 in Group B. Retromolar space/width ratio was 1.22 +/- 0.20 for Group A and 0.82 +/- 0.34 for Group B. Mean angulations in Group A was 5.98 +/- 5.9 degrees whereas 34.56 +/- 27.89 degrees in Group B.
  
  
  CONCLUSIONS
  The probability of eruption of the lower third molar increases if retromolar space measured from anterior edge of ramus (AER-7) and centre of rumus point (Xi-7) is 13mm and 25mm respectively, provided the space/width ratio is greater than 1 and angulation is also vertical. Mesiodistal width of the tooth has no significant role in impactions.
authors.affiliation: Department of Orthodontics, Baqai Dental College, Karachi.
authors.forename: Irfan
authors.initials: I
authors.lastname: Qamruddin
authors.forename: Wasif
authors.initials: W
authors.lastname: Qayyum
authors.forename: Syed Mahmood
authors.initials: SM
authors.lastname: Haider
authors.forename: Seema Wasif
authors.initials: SW
authors.lastname: Siddiqui
authors.forename: Faisal
authors.initials: F
authors.lastname: Rehan
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging; D008964:Molar, Third / Q000000981:diagnostic imaging*; D009811:Odontometry / Q000379:methods; D011237:Predictive Value of Tests; D011862:Radiography, Panoramic / Q000379:methods* / Q000592:standards; D014078:Tooth Eruption; D014095:Tooth, Impacted / Q000000981:diagnostic imaging*; D014097:Tooth, Unerupted / Q000000981:diagnostic imaging*