title: The Callander laryngoscope blade modification is associated with a decreased risk of dental contact.
abstract: OBJECTIVE
  Dental damage may occur with laryngoscopy. The purpose of this study was twofold: to determine whether preoperative examination could predict the risk of contacting the teeth with the laryngoscope and to evaluate the effectiveness of a modified Macintosh blade on reducing dental contact.
  
  
  METHODS
  Four hundred and eighty-three patients scheduled for elective surgery requiring general anesthesia with endotracheal tube placement were studied prospectively. Features that might predict difficult intubation were assessed preoperatively. Laryngoscopy was performed twice on each patient, once with a regular Macintosh 3 blade and once with a blade in which the flange was partially removed (Callander modification). The distance between the flange of the blade and the upper incisors at glottic exposure was measured. We calculated correlations between individual airway characteristics and the chance of hitting the upper teeth with the regular Macintosh 3 blade and compared the frequencies of contacting the teeth between the two blades.
  
  
  RESULTS
  The chance of hitting the upper teeth when using the regular Macintosh 3 blade increased significantly with non-parametric scores for Mallampati classification, mandibular subluxation, head and neck movement, interincisor gap, and condition of the upper teeth. (P < 0.01) The frequency of direct contact varied significantly between the two blades: 20.3% vs 4.1% for Macintosh 3 and modified blades, respectively (P < 0.05). Laryngeal views were improved with the modified blade.
  
  
  CONCLUSIONS
  Airway characteristics correlate with the risk of hitting the upper teeth during laryngoscopy. The modified Macintosh blade reduces the risk of contacting the teeth.
authors.affiliation: Department of Anesthesiology, School of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Jaemin
authors.initials: J
authors.lastname: Lee
authors.forename: Jong H
authors.initials: JH
authors.lastname: Choi
authors.forename: Yoon K
authors.initials: YK
authors.lastname: Lee
authors.forename: Eun S
authors.initials: ES
authors.lastname: Kim
authors.forename: Ou K
authors.initials: OK
authors.lastname: Kwon
authors.forename: Randolph H
authors.initials: RH
authors.lastname: Hastings
mesh_terms: D000328:Adult; D000768:Anesthesia, General; D016009:Chi-Square Distribution; D004867:Equipment Design; D005260:Female; D006801:Humans; D007442:Intubation, Intratracheal / Q000295:instrumentation / Q000379:methods; D020704:Laryngoscopes / Q000009:adverse effects* / Q000592:standards*; D008297:Male; D011446:Prospective Studies; D012307:Risk Factors; D018709:Statistics, Nonparametric; D018677:Tooth Injuries / Q000209:etiology* / Q000517:prevention & control*