Mechanical Principles Involved in Tooth Extraction 1

Principles of Elevator and Forceps Use

1. EXODONTIA Mechanical Principles Involved in Tooth Extraction 1   Senior Lecturer Dr. Haydar Munir Salih Alnamir BDS, PhD (Board Certified)

2. Mechanical Principles Involved in Tooth Extraction The removal of teeth from the alveolar process requires the use of the following mechanical principles and simple machines: the lever, the wedge, and the wheel and axle.

3. The lever action Elevators are used primarily as levers. A lever is a mechanism for transmitting a modest force—with the mechanical advantages of a long lever arm and a short effector arm—into a small movement against great resistance An example of the use of a lever is when a Crane pick is inserted into a purchase point placed in a tooth and then is used to elevate the tooth

4. The lever action

5. The wedge action The wedge is useful in several different ways for the extraction of teeth. First , the beaks of extraction forceps are usually narrow at their tips; they broaden as they go superiorly. When forceps are used, there should be a conscious effort made to force the tips of the forceps into the periodontal ligament space at the bony crest. This uses the tooth root as a wedge to expand the bone; as the beaks of the forceps are pressed apically on the root, they will help force the tooth out of the socket 

6. 2. The wedge action

7. 2. The wedge action The wedge principle is also useful when a straight elevator is used to luxate a tooth from its socket. A small elevator is wedged into the periodontal ligament space, which displaces the root toward the occlusion and thus out of the socket 

8. 3. The wheel and axle action the wheel and axle, which is most closely identified with the triangular, or pennant- shaped, elevator. When one root of a multiple-rooted tooth is left in the alveolar process, the pennant-shaped elevator, such as a Cryer, is positioned into the socket and turned. The handle then serves as the axle, and the tip of the triangular elevator acts as a wheel and engages and elevates the tooth root from the socket

9. 3. The wheel and axle action

10. The goal of forceps use is threefold: (1) expansion of the bony socket by use of the wedge-shaped beaks of the forceps and the movements of the tooth itself with the forceps, (2) twisting of conical roots to disrupt periodontal ligaments, and (3) removal of the tooth from the socket.

11. The goal of forceps use

12. Forceps can apply five major motions to luxate teeth. The first is apical pressure, which accomplishes two goals. (1) Although the tooth moves in an apical direction minimally, the tooth socket is expanded by the insertion of the beaks down into the periodontal ligament space

13. 1. Apical pressure (2) A second accomplishment of apical pressure is that the center of rotation of the tooth is displaced apically which results in greater movement of the expansion forces at the crest of the ridge and less force moving the apex of the tooth lingually .This process decreases the chance for apical root fracture .

14. Forceps can apply five major motions to luxate teeth. The second major pressure or movement applied by forceps is the buccal force . Buccal pressures result in expansion of the buccal plate, particularly at the crest of the ridge . Although buccal pressure causes expansion forces at the crest of the ridge, it is important to remember that it also causes lingual apical pressure. Thus excessive force can fracture buccal bone or cause fracturing of the apical portion of the root .

15. 2. The buccal force

16. Forceps can apply five major motions to luxate teeth. Third, lingual or palatal pressure is similar to the concept of buccal pressure but is aimed at expanding the linguo-crestal bone and, at the same time, avoiding excessive pressures on the buccal apical bone. Because lingual bone tends to be thicker than buccal bone in posterior areas of the mouth, limited bone expansion occurs.

17. 3. Lingual or palatal pressure

18. Forceps can apply five major motions to luxate teeth. Because maxillary buccal bone is usually thinner and palatal bone is a thicker cortical bone, maxillary teeth are usually removed by stronger buccal forces and less vigorous palatal forces. In the mandible , buccal bone is thinner from the midline posteriorly to the area of molars. Therefore incisors, canines, and premolars are removed primarily as a result of strong sustained buccal force and less vigorous lingual pressures.

19. Forceps can apply five major motions to luxate teeth. Fourth, rotational pressure , as the name implies, rotates the tooth, which causes some internal expansion of the tooth socket and tearing of periodontal ligaments. Teeth with single, conical roots (such as incisors, canines, and mandibular premolars) and those with roots that are not curved are most amenable to luxation by this technique .Teeth that have other than conical roots or that have multiple roots—especially if those roots are curved—are more likely to fracture under this type of pressure.

20. 4. Rotational pressure

21. Forceps can apply five major motions to luxate teeth. Finally, tractional forces are useful for delivering the tooth from the socket once adequate bony expansion is achieved. As mentioned previously, teeth should not be pulled from their sockets. Tractional forces should be limited to the final portion of the extraction process and should be gentle . If excessive force is needed, other maneuvers should be performed to improve root luxation

22. 5. Tractional forces

23. Procedure for Closed Extraction The correct technique for any situation should lead to an atraumatic extraction; the wrong technique commonly results in an excessively traumatic and lengthy extraction. Whatever technique is chosen, the three fundamental requirements for a good extraction remain the same: (1) adequate access and visualization of the field of surgery, (2) an unimpeded pathway for the removal of the tooth, and (3) the use of controlled force to luxate and remove the tooth.  

24. General steps make up the closed extraction procedure. Step 1 involves loosening of the soft tissue attachment from the cervical portion of the tooth . The purpose of loosening the soft tissue from the tooth is twofold: (1) First, it allows the surgeon to ensure that profound anesthesia has been achieved (2) The second reason that soft tissue is loosened is to allow the elevator and tooth extraction forceps to be positioned more apically, without interference from or impingement on the gingiva

25. Step 1 involves loosening of the soft tissue attachment from the cervical portion of the tooth .

26. General steps make up the closed extraction procedure. Step 2 involves luxation of the tooth with a dental elevator . The luxation of the tooth begins with a dental elevator, usually the straight elevator Elevation should occur at the mesial and distal buccal aspects of the root. No elevation should be attempted along buccal bone because it can be easily fractured or the surgeon can lose control and cause soft tissue injury.

27. Step 2 involves luxation of the tooth with a dental elevator The straight elevator is inserted perpendicular to the tooth into the interdental space, after reflection of the interdental papilla Luxation of teeth with a straight elevator should be performed with caution. Excessive forces can damage and even displace the teeth adjacent to those being extracted.

28. Step 2 involves luxation of the tooth with a dental elevator

29. General steps make up the closed extraction procedure. Step 3 involves adaptation of the forceps to the tooth . The proper forceps are now chosen for the tooth to be extracted. The beaks of the forceps should be shaped to adapt anatomically to the tooth, apical to the cervical line, that is, to the root surface. (A few exceptions to this include the cowhorn forceps.)

30. Step 3 involves adaptation of the forceps to the tooth . Care must be taken to confirm that the tips of the forceps beaks are beneath the soft tissue and not engaging an adjacent tooth. The beaks of the forceps must be held parallel to the long axis of the tooth so that the forces generated by the application of pressure to the forceps handle can be delivered along the long axis of the tooth for maximal effectiveness in dilating and expanding alveolar bone The forceps are then forced apically as far as possible to grasp the root of the tooth as apically as possible

31. Step 3 involves adaptation of the forceps to the tooth .

32. General steps make up the closed extraction procedure. Step 4 involves luxation of the tooth with forceps . The major portion of the force is directed toward the thinnest and therefore weakest bone. Thus, with all teeth in the maxilla and all but molar teeth in the mandible, the major movement is labial and buccal (i.e., toward the thinner layer of bone). The surgeon uses slow, sustained, steady force to displace the tooth buccally, rather than a series of rapid, small movements that do little to expand bone . The motion is deliberate and slow, and it gradually increases in force. The tooth is then moved again toward the opposite direction with slow, deliberate, strong pressure

33. The following three factors must be reemphasized (1) The forceps must be apically seated as far as possible and reseated periodically during the extraction; ( 2) the forces applied in the buccal and lingual directions should be slow, deliberate pressures and not jerky wiggles; and ( 3) the force should be held for several seconds to allow the bone time to expand.

34. Step 4 involves luxation of the tooth with forceps .

35. Step 4 involves luxation of the tooth with forceps .

36. General steps make up the closed extraction procedure. Step 5 involves removal of the tooth from the socket. Once alveolar bone has expanded sufficiently and the tooth has been luxated, a slight tractional force, usually directed buccally, can be used. Tractional forces should be minimized because this is the last motion that is used once the alveolar process is sufficiently expanded and the periodontal ligament is completely severed

37. Role of the Opposite Hand (1) The left hand is responsible for reflecting the soft tissues of the cheeks, lips, and tongue to provide adequate visualization of the area of surgery . The left hand helps protect other teeth from the forceps, should it release suddenly from the tooth socket. (2) The left hand, and sometimes arm, helps stabilize the patient’s head during the extraction process. In some situations, greater amounts of force are required to expand heavy alveolar bone; therefore the patient’s head requires active assistance to be held steady.

38. Role of the Opposite Hand

39. Role of the Opposite Hand 3) The opposite hand plays an important role in supporting and stabilizing the jaw when mandibular teeth are being extracted. The opposite hand is often necessary to apply considerable pressure to expand heavy mandibular bone, and such forces can cause discomfort and even injury to the TMJ unless a steady hand counteracts them. ( 4) Finally, the opposite hand supports the alveolar process and provides tactile information to the operator concerning the expansion of the alveolar process during the luxation period.

40. Role of the Opposite Hand