title: Pell-Gregory classification is unreliable as a predictor of difficulty in extracting impacted lower third molars.
abstract: We present a study of 166 extractions of impacted lower third molars, all vertical and all extracted by the same surgeon. Each tooth was classified according to the Pell-Gregory scales of position for the occlusal plane (scale A-C) and the ascending ram us of the mandible (scale 1-3). The extraction was subsequently rated as 'easy' or 'difficult'.Taking Pell-Gregory class C as a predictor of a 'difficult' extraction, specificity was 88% but sensitivity was low at 15%. Taking Pell-Gregory class 3 as an indicator of 'difficult', sensitivity was somewhat better (50%), but at the expense of specificity (62%). Likelihood ratios for the individual classes also indicated that the scales are of little value for predicting a difficult extraction.
authors.affiliation: Head of Section, Department of Maxillofacial Surgery, Oral Surgery Unit, School of Dentistry, Facultad de Odontología, University of Santiago de Compostela, Santiago de Compostela, Spain.
authors.forename: A G
authors.initials: AG
authors.lastname: García
authors.forename: F G
authors.initials: FG
authors.lastname: Sampedro
authors.forename: J G
authors.initials: JG
authors.lastname: Rey
authors.forename: P G
authors.initials: PG
authors.lastname: Vila
authors.forename: M S
authors.initials: MS
authors.lastname: Martin
mesh_terms: D005544:Forecasting; D006801:Humans; D016013:Likelihood Functions; D008334:Mandible; D008964:Molar, Third / Q000473:pathology / Q000601:surgery*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014081:Tooth Extraction / Q000145:classification*; D014095:Tooth, Impacted / Q000145:classification* / Q000473:pathology / Q000601:surgery*