Springer Nature is making SARS-CoV-2 and COVID-19 research free. View research | View latest news | Sign up for updates

Transverse forces exerted on the maxillary incisors during laryngoscopy



In this study the effect of level of experience of the intubator on the forces applied by the Macintosh laryngoscope on the maxillary incisors in both the axial and transverse direction were investigated.


Five groups of different levels of experience (15 per group), staff anaesthetists, residents, nurse anaesthetists, surgeons and students, performed one laryngoscopy and subsequent intubation on an intubation manikin equipped with sensors to measure these forces.


Maximal transverse forces oriented toward the base of the skull (Fmtpmax) were between 0 and 10 N in 46 cases (61%), between 10 and 20 N in 21 (28%) and ≥ 20 N (maximum 46.5 N) in eight cases (11%). The maximal values of the transverse forces oriented toward the intubator (Fmtnmax) were between 0 and 10 N in 69 cases (92%), between 10 and 20 N in 3 (4%) and ≥ 20 N (maximum 36.4 N) in 3 (4%). Level of experience was related to Fmtpmax (Spearman: P = 0.04, r = 0.24). In addition, Fmtnmax was less in experienced intubators (anaesthetist and residents) than in inexperienced intubators (all other groups) (Student’s t test: P = 0.04).


In contrast to the effect on forces exerted in the axial direction, experience proved to have a beneficial effect on the forces in the transverse direction.



Vérifier l’influence de l’expérience de l’intubateur sur les forces appliquées par le laryngoscope Macintosh sur les incisives maxillaires tant dans la direction transversale qu’axiale.


Cinq groupes possédant des degrés variés d’expérience (15 par groupe) anesthésistes, résidents, infirmières anesthésistes, chirurgiens et étudiants ont effectué une laryngoscopie suivie de l’intubation sur un mannequin d’intubation équipé de senseurs capables de mesurer ces forces.


Les forces transversales maximales orientées vers la base du crâne (Fmtpmax) se situaient entre 0 et 10 N dans 46 cas (61%), entre 10 et 20 N dans 21 (28%) et ≥ 20 N (maximum 46,5 N) dans huit cas (11%). Les valeurs maximales des forces orientées vers l’intubateur (Fmtnmax) se situaient entre 0 et 10 N dans 69 cas (92%), entre 10 et 20 N dans 3 (4%) et ≥ 20 N (maximum 26,4 N) dans 3 (4%). Le degré d’expérience était en rapport avec Fmtpmax (Spearman: P = 0,04, r = 0,24). De plus, Fmtnmax était plus bas chez les intubateurs expérimentés (anesthésistes et résidents) que chez les intubateurs inexpérimentés (tous les autres groupes) (test t de Student: P = 0,04).


Contrairement aux forces exercées en direction axiale, l’expérience a une influence bénéfique sur les forces exercées en direction transversale.


  1. 1

    Otto CW. Trachéal Intubation.In: Nunn JF, Utting JE, Brown BR Jr (Ed.). General Anaesthesia, 5th ed. London: Butterworths, 1989: 512–39.

  2. 2

    Roberts JT. Fundamentals of Tracheal Intubation. Boston, Massachusetts: Grune & Stratton, 1983: 75–80.

  3. 3

    Bucx MJL, Snijders CJ, van Geel RTM, et al. Forces acting on maxillary incisor teeth during laryngoscopy using the Macintosh laryngoscope. Anaesthesia 1994; 49: 1064–70.

  4. 4

    Bucx MJL, van Geel RTM, Wegener JT, Robers C, Stijnen T. Does experience influence the forces exerted on maxillary incisors during laryngoscopy? A manikin study using the Macintosh laryngoscope. Can J Anaesth 1995; 42: 144–9.

  5. 5

    Andreasen JO, Andreasen FM. Textbook and Color Atlas of Traumatic Injuries to the Teeth, 3rd ed. Copenhagen: Munksgaard, 1994: 162–4.

  6. 6

    Bucx MJL, Scheck PAE, van Geel RTM, den Ouden AH, Niesing R. Measurement of forces during laryngoscopy. Anaesthesia 1992; 47: 348–51.

  7. 7

    Pronk CNA, Niesing R. Measuring hand-grip force, using a new application of strain gauges. Med Biol Eng Comput, 1981; 19: 127–8.

  8. 8

    Cormack RS, Lehane J. Difficult tracheal intubation in obstetrics. Anaesthesia 1984; 39: 1105–11.

  9. 9

    Burton JF, Baker AB. Dental damage during anaesthesia and surgery. Anaesth Intensive Care 1987; 15: 262–8.

  10. 10

    Clokie C, Metcalf I, Holland A. Dental trauma in anaesthesia. Can J Anaesth 1989; 36: 675–80.

  11. 11

    Andreasen FM, Yu Z, Thomsen BL, Andersen PK. Occurrence of pulp canal obliteration after luxation injuries in the permanent dentition. Endodontics and Dental Traumatology 1987; 3: 103–15.

  12. 12

    Bishop MJ, Harrington RM, Tencer AF. Force applied during tracheal intubation. Anesth Analg 1992; 74: 411–4.

  13. 13

    Chopra V, Gesink BJ, de Jong F, Bovill JG, Spierdijk J, Brand R. Does training on an anaesthesia simulator lead to improvement in performance? Br J Anaesth 1994; 73: 293–7.

Download references

Author information

Correspondence to Martin J. L. Bucx.

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Bucx, M.J.L., van der Vegt, M.H., Snijders, C.J. et al. Transverse forces exerted on the maxillary incisors during laryngoscopy. Can J Anesth 43, 665 (1996). https://doi.org/10.1007/BF03017948

Download citation

Key words

  • anaesthetic techniques: laryngoscopy
  • equipment: laryngoscopes
  • intubation, tracheal: technique
  • larynx: laryngoscopy