Videolaryngoscopy results in less forces exerted on the upper teeth during intubation compared to direct laryngoscopy

INTERVENTION: After three minutes of oxygen administration via facemask, intravenous (iv) induction of general anesthesia (1 µg/kg fentanyl, 3 mg/kg propofol and 0.7 mg/kg rocuronium) the following interventions will be performed: Direct laryngoscopy: 1. Macintosh classic laryngoscope (blade III) Indirect laryngoscopy with one of three indirect videolaryngoscopes: 1. McGrath (Aircraft Medical, Edinburgh, UK) 2. C‐MAC (Karl Storz, Tuttlingen, Germany) 3. Glidescope Cobalt (Verathon, Bothell, WA, USA) Intubation: endotracheal tube 7.5 mm (female) or 8.0 mm (male). After two unsuccessful attempts a stylet will be inserted into the endotracheal tube. CONDITION: Intubation technique ; Surgery ; Intubation technique PRIMARY OUTCOME: Differences between direct and indirect laryngoscopies with respect to the frequency with which forces are applied on the upper and lower teeth. The measurement of forces will be performed with Flexiforce (r) sensors (A201‐25, Tekscan, MA) fixed to the blade of the laryngoscope at the possible area of contact with the teeth. SECONDARY OUTCOME: For the cases in which forces are being applied, differs the magnitude of forces between the laryngoscopes? INCLUSION CRITERIA: 1. American Society of Anaesthesiologists (ASA) grade I ‐ II 2. Normal airway 3. Undergoing a surgical intervention for which endotracheal intubation is indicated 4. Aged 18 years or above, either sex