title: Maxillary third molar: patterns of impaction and their relation to oroantral perforation.
abstract: OBJECTIVE
  The objectives of this study were to examine 1) the patterns of the impacted maxillary wisdom tooth and 2) the proximity of the impacted maxillary wisdom tooth to the maxillary sinus in relation to oroantral perforation during the removal of a maxillary wisdom tooth.
  
  
  METHODS
  This retrospective study reviewed the clinical records and dental pantomograms of patients who underwent the removal of maxillary wisdom teeth under general anesthesia over a 6-month period. Using a modified version of the Archer classification of impacted maxillary wisdom teeth, types of impaction were classified according to depth, angulation of impaction, and proximity to the floor of the sinus. Clinical records showed the occurrence of oroantral perforation.
  
  
  RESULTS
  In total, 845 maxillary wisdom teeth were removed; 66.8% were by routine extraction and 33.2% were removed surgically. The most common type of impaction was vertical followed by mesioangular. Most impacted teeth were at the level between the occlusal and cervical level of the adjacent second molar. Only 7 of the 278 excised wisdom teeth produced an oroantral perforation. Only 0.9% of all cases with a close sinus approximation showed an oroantral perforation. Statistical analysis with the Fisher exact test showed statistically significant associations of depth of impaction (P < .001), eruption status (P = .001), and long-axis position (P < .001) to the occurrence of an oroantral perforation. Sinus approximation showed no association with the occurrence of an oroantral perforation (P = 1.000).
  
  
  CONCLUSIONS
  The depth of impaction of the maxillary wisdom tooth is a possible predictor of the possibility of oro-antral perforation if removal of the tooth is required. Due to the limitation of the radiograph, it is not a reliable to use radiographic close proximity of the sinus to predict the occurrence of oro-antral perforation when the maxillary wisdom tooth is removed.
authors.affiliation: Department of Oral and Maxillofacial Surgery, University Dental Cluster, National University Hospital, Singapore. asher_lim@nuhs.edu.sg
authors.forename: Asher Ah Tong
authors.initials: AA
authors.lastname: Lim
authors.forename: Chin Wee
authors.initials: CW
authors.lastname: Wong
authors.forename: John C
authors.initials: JC
authors.lastname: Allen
mesh_terms: D000293:Adolescent; D000328:Adult; D002508:Cephalometry; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007431:Intraoperative Complications / Q000601:surgery; D008297:Male; D008437:Maxilla / Q000293:injuries / Q000601:surgery*; D008443:Maxillary Sinus / Q000000981:diagnostic imaging / Q000293:injuries; D008875:Middle Aged; D008964:Molar, Third / Q000000981:diagnostic imaging / Q000601:surgery*; D009957:Oroantral Fistula / Q000209:etiology* / Q000601:surgery; D011862:Radiography, Panoramic; D012189:Retrospective Studies; D014081:Tooth Extraction / Q000379:methods; D014095:Tooth, Impacted / Q000145:classification / Q000000981:diagnostic imaging / Q000601:surgery*; D014097:Tooth, Unerupted / Q000145:classification / Q000000981:diagnostic imaging / Q000601:surgery; D055815:Young Adult