Pell-Gregory classification is unreliable as a predictor of difficulty in extracting impacted lower third molars.
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.
García
A G
AG
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.
Sampedro
F G
FG
Rey
J G
JG
Vila
P G
PG
Martin
M S
MS
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*