Inferior alveolar nerve block in dentistry

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1. Inferior alveolar nerve block SHORT TOPIC PRESENTATION ELDHO GEORGE JR 1

2. contents INTRODUCTION INDICATIONS AND CONTRAINDICATIONS ADVANTAGES AND DISADVANTAGES ALTERNATIVES TO IANB TECHNIQUE SIGNS AND SYMPTOMS FAILURE OF ANESTHESIA COMPLICATIONS REFERENCES

3. INTRODUCTION The IANB, commonly referred to as the mandibular nerve block, is the second most frequently used (after infiltration) and possibly the most important injection technique in dentistry. Unfortunately, it also proves to be the most frustrating, with the highest percentage of clinical failures even when administered properly

4. A supplemental block (buccal nerve) is needed only when soft tissue anesthesia in the buccal posterior region is necessary Intraosseous anesthesia is a supplemental technique used, usually on molars, when the IANB has proven ineffective, primarily when the tooth is pulpally involved Administration of bilateral IANBs is rarely indicated in dental treatments other than bilateral mandibular surgical procedures.

5. Nerves Anesthetized 1. Inferior alveolar nerve, a branch of the posterior division of the mandibular division of the trigeminal nerve (V3) 2. Incisive nerve 3. Mental nerve 4. Lingual nerve (commonly)

6. Areas Anesthetized 1. Mandibular teeth to the midline 2. Body of the mandible, inferior portion of the ramus 3. Buccal mucoperiosteum, mucous membrane anterior to the mental foramen (mental nerve) 4. Anterior two-thirds of the tongue and floor of the oral cavity (lingual nerve) 5. Lingual soft tissues and periosteum (lingual nerve)

7. Indications 1. Procedures on multiple mandibular teeth in one quadrant 2. When buccal soft tissue anesthesia (anterior to the mental foramen) is necessary 3. When lingual soft tissue anesthesia is necessary

8. Contraindications 1. Infection or acute inflammation in the area of injection (rare) 2. Patients who are more likely to bite their lip or tongue (e.g., a very young child or a physically or mentally handicapped adult or child)

9. Advantages One injection provides a wide area of anesthesia (useful for quadrant dentistry) Disadvantages 1. Wide area of anesthesia (not indicated for localized procedures) 2. Rate of inadequate anesthesia (31% to 81%) 3. Intraoral landmarks not consistently reliable 4. Positive aspiration (10% to 15%, highest of all intraoral injection techniques)

10. 5. Lingual and lower-lip anesthesia, discomforting to many patients and possibly dangerous (self-inflicted soft tissue trauma) for certain individuals 6. Partial anesthesia possible where a bifid IAN and bifid mandibular canals are present; cross-innervation in lower anterior region

11. Alternatives to ianb 1. Mental nerve block, for buccal soft tissue anesthesia anterior to the first molar 2. Incisive nerve block, for pulpal and buccal soft tissue anesthesia of teeth anterior to the mental foramen (usually second premolar to central incisor) 3. Supraperiosteal injection, for pulpal anesthesia of the central and lateral incisors, and sometimes the premolars and molars

12. 4. Gow -Gates mandibular nerve block 5. Vazirani-Akinosi mandibular nerve block 6. PDL injection for pulpal anesthesia of any mandibular tooth 7. Intraosseous injection for pulpal and soft tissue anesthesia of any mandibular tooth, but especially molars 8. Intraseptal injection for pulpal and soft tissue anesthesia of any mandibular tooth

13. technique A long dental needle is recommended for the adult patient or any pediatric patient where the soft tissue depth at the injection site is approximately 20 mm. A 25-gauge long needle is preferred; a 27-gauge long is acceptable Area of insertion: mucous membrane on the medial (lingual) side of the mandibular ramus, at the intersection of two lines—one horizontal, representing the height of needle insertion, the other vertical, representing the anteroposterior plane of injection

14. Target area: inferior alveolar nerve as it passes downward toward the mandibular foramen but before it enters into the foramen Landmarks: a. Coronoid notch (greatest concavity on the anterior border of the ramus) b. Pterygomandibular raphe (vertical portion) c. Occlusal plane of the mandibular posterior teeth

15. Procedure: Assume the correct position: For a right IANB, a right-handed administrator should sit at the 8 o’clock position facing the patient For a left IANB, a right-handed administrator should sit at the 10 o’clock position facing in the same direction as the patient

16. B . Position the patient supine (recommended) or semisupine (if necessary). The mouth should be opened wide to allow greater visibility of, and access to, the injection site. C. Prepare tissue at the injection site: 1. Dry it with sterile gauze. 2. Apply topical antiseptic (optional). 3. Apply topical anesthetic for 1 to 2 minutes

17. D. Place the barrel of the syringe in the corner of the mouth on the contralateral side E. Locate the needle penetration (injection) site

18. Three parameters must be considered during administration of an IANB: (1) The height of the injection (2) The anteroposterior placement of the needle (which helps to locate a precise needle entry point) (3) The depth of penetration (which determines the location of the inferior alveolar nerve).

19. Height of injection Place the index finger or the thumb of your left hand in the coronoid notch a. An imaginary line extends posteriorly from the fingertip in the coronoid notch to the deepest part of the pterygomandibular raphe (as it turns vertically upward toward the maxilla), determining the height of injection. This imaginary line should be parallel to the occlusal plane of the mandibular molar teeth. In most patients, this line lies 6 to 10 mm above the occlusal plane

20. b. The finger on the coronoid notch is used to pull the tissues laterally, stretching them over the injection site, making them taut, and enabling needle insertion to be less traumatic, while providing better visibility. If possible, use a mouth mirror to minimize the risk of accidental needlestick injury to the administrator c.The needle insertion point lies three-fourths of the anteroposterior distance from the coronoid notch back to the deepest part of the pterygomandibular raphe: The line should begin at the midpoint of the notch and terminate at the deepest (most posterior) portion of the pterygomandibular raphe as the raphe bends vertically upward toward the palate

21. d. The posterior border of the mandibular ramus can be approximated intraorally by use of the pterygomandibular raphe as it bends vertically upward toward the maxilla An alternative method of approximating the length of the ramus is to place your thumb on the coronoid notch and your index finger extraorally on the posterior border of the ramus and estimate the distance between these points. However, many practitioners have difficulty envisioning the width of the ramus in this manner.

22. Anteroposterior site of injection Needle penetration occurs at the intersection of two points.

23. a. Point 1 falls along the horizontal line from the coronoid notch to the deepest part of the pterygomandibular raphe as it ascends vertically toward the palate as just described. b. Point 2 is on a vertical line through point 1 about three-fourths of the distance from the anterior border of the ramus. This determines the anteroposterior site of the injection

24. Penetration depth In the third parameter of the IANB, bone should be contacted. Slowly advance the needle until you can feel it contact bone

25. a. For most patients, it is not necessary to inject any local anesthetic solution as soft tissue is penetrated. b. For anxious or sensitive patients, it may be advisable to deposit small volumes as the needle is advanced. Buffered local anesthetic solutions are recommended as they decrease the patient’s sensitivity during needle advancement c. The average depth of penetration to bony contact, in the adult, is 20 to 25 mm, approximately two-thirds to three-fourths the length of a long dental needle

26. d. The needle tip should now be located slightly superior to the mandibular foramen (where the IAN enters [disappears into] bone). The foramen can neither be seen nor be palpated clinically. e. If bone is contacted too soon (less than half the length of a long dental needle in an adult), the needle tip is usually located too far anteriorly on the ramus

27. i . Withdraw the needle slightly but do not remove it from the tissue. ii. Bring the syringe barrel more toward the front of the mouth, over the canine or lateral incisor on the contralateral side. iii. Redirect the needle until a more appropriate depth of insertion is obtained. The needle tip is now located more posteriorly in the mandibular sulcus

28. f. If bone is not contacted, the needle tip is usually located too far posterior (medial) . To correct this: i . Withdraw it slightly in tissue (leaving approximately one-fourth of its length in tissue) and reposition the syringe barrel more posteriorly (over the mandibular molars). ii. Continue needle insertion until contact with bone is made at an appropriate depth (20 to 25 mm).

29. Insert the needle. When bone is contacted, withdraw approximately the needle by 1 mm to prevent subperiosteal injection. Aspirate in two planes. If negative, slowly deposit 1.5 mL of anesthetic over a minimum of 60 seconds. (Because of the high incidence of positive aspiration and the natural tendency to deposit solution too rapidly, the sequence of slow injection, reaspiration , slow injection, and reaspiration is strongly recommended.) Slowly withdraw the syringe, and when approximately half its length remains within tissues, reaspirate . If negative, deposit a portion of the remaining solution (0.2 mL) to anesthetize the lingual nerve.

30. In most patients, this deliberate injection for lingual nerve anesthesia is not necessary because local anesthetic from the IANB anesthetizes the lingual nerve Withdraw the syringe slowly and make the needle safe. After approximately 20 seconds, return the patient to a comfortably upright or semiupright position.

31. Wait 3 to 5 minutes before testing for pulpal anesthesia. Following completion of the IANB, the author strongly recommends the infiltration of approximately 0.6 to 0.9 mL of articaine hydrochloride (preferably buffered) in the buccal fold at the apex of each mandibular tooth to be treated. This has been demonstrated to increase the success rate of IANBs (as well as other “ mandibular”nerve blocks)

32. Signs and Symptoms 1. Subjective: Tingling or numbness of the lower lip indicates anesthesia of the mental nerve, a terminal branch of the inferior alveolar nerve. This is a good indication that the IAN is anesthetized, although it is not a reliable indicator of the depth of anesthesia. Soft tissue anesthesia is never a guarantee of pulpal anesthesia. 2. Subjective: Tingling or numbness of the tongue indicates anesthesia of the lingual nerve, a branch of the posterior division of V3.

33. 3. Objective: Use of a freezing spray (e.g., Endo-Ice) or an electric pulp tester (EPT) with no response to maximal output (80/80) on two consecutive tests at least 2 minutes apart serves as a “guarantee” (∼99%) of successful pulpal anesthesia in nonpulpitic teeth. 4. Objective: No pain is felt during dental therapy

34. Safety Feature The needle contacts bone, preventing overinsertion with its attendant complications.

35. Precautions 1. Do not deposit local anesthetic if bone is not contacted. The needle tip may be resting within the parotid gland near the facial nerve (cranial nerve VII), and a transient blockade (paralysis) of the facial nerve may develop if local anesthetic solution is deposited. 2. Avoid pain by not contacting bone too forcefully.

36. Failures of Anesthesia The most common causes of absent or incomplete IANB are: 1. Deposition of anesthetic too low (below the mandibular foramen). To correct this, reinject anesthetic at a higher site (approximately 5 to 10 mm above the previous site). 2. Deposition of the anesthetic too far anteriorly (laterally) on the ramus. This is diagnosed by lack of anesthesia except at the injection site and by the minimum depth of needle penetration before contact with bone (e.g., the [long] needle is usually less than halfway into tissue). To correct this, redirect the needle tip posteriorly

37. 3. Accessory innervation to the mandibular teeth: a. The primary symptom is isolated areas of incomplete pulpal anesthesia encountered in the mandibular molars (most commonly the mesial portion of the mandibular first molar). b. Although it has been postulated that several nerves provide the mandibular teeth with accessory sensory innervation (e.g., the cervical accessory and mylohyoid nerves), current thinking supports the mylohyoid nerve as the prime candidate.

38. The Gow -Gates mandibular nerve block, which routinely blocks the mylohyoid nerve, is not associated with problems of accessory innervation (unlike the IANB, which normally does not block the mylohyoid nerve).

39. To correct this: Technique 1: a. Use a 25-gauge (or 27-gauge) long needle. b. Retract the tongue toward the midline with a mirror handle or tongue depressor to provide access and visibility to the lingual border of the body of the mandible

40. c. Place the syringe in the corner of mouth on the opposite side and direct the needle tip to the apical region of the tooth immediately posterior to the tooth in question (e.g., the apex of the second molar if the first molar is the problem). d. Penetrate the soft tissues and advance the needle until bone (e.g., the lingual border of the body of the mandible) is contacted. Topical anesthesia is unnecessary if lingual anesthesia is already present. The depth of penetration to bone is 3 to 5 mm

41. e. Aspirate in two planes. If negative, slowly deposit approximately 0.6 mL (one-third of a cartridge) of anesthetic (in about 20 seconds). f. Withdraw the syringe and make the needle safe

42. Technique 2. In any situation in which partial anesthesia of a tooth occurs, a PDL or intraosseous injection may be administered; both techniques have a high expectation of success. d. Whenever a bifid IAN is detected on the radiograph, incomplete anesthesia of the mandible may develop after IANB. In many such cases, a second mandibular foramen, located more inferiorly, exists. To correct this, deposit a volume of solution inferior to the normal anatomic landmark.

43. 4. Incomplete anesthesia of the central or lateral incisors: a. This may comprise isolated areas of incomplete pulpal anesthesia. b. Often this is caused by overlapping fibers of the contralateral inferior alveolar nerve, although it may also arise (rarely) from innervation from the mylohyoid nerve.

44. To correct this: Technique 1 a. Infiltrate 0.9 mL of local anesthetic solution supraperiosteally into the mucobuccal fold below the apex of the tooth in question. This is generally highly effective in the central and lateral incisor teeth because of the many small nutrient canals in the cortical bone near the region of the incisive fossa. The local anesthetic articaine hydrochloride appears to have the greatest success

45. b. A 27-gauge short needle is recommended c. Direct the needle tip toward the apical region of the tooth in question. Topical anesthesia is not necessary if mental nerve anesthesia is present. d. Aspirate in two planes. e. If negative, slowly deposit 0.9 mL of local anesthetic solution in approximately 30 seconds. f. Wait about 5 minutes before starting the dental procedure.

46. Technique 2 As an alternative, PDL injection may be used. PDL injection has great success in the mandibular anterior region

47. Complications 1. Hematoma (rare): a. Swelling of tissues on the medial side of the mandibular ramus after the deposition of anesthetic. b. Management: apply pressure to the area for a minimum of 3 to 5 m

48. 2. Trismus: a. Muscle soreness or limited opening of mandible: i . A slight degree of soreness when opening the mandible is extremely common after IANB (after anesthesia has dissipated). ii. More severe soreness associated with limited mandibular opening is rare.

49. 3. Transient facial paralysis (facial nerve anesthesia): a. Produced by the deposition of local anesthetic into the body of the parotid gland, blocking cranial nerve VII (facial nerve), a motor nerve to the muscles of facial expression. Signs and symptoms include an inability to close the lower eyelid and drooping of the upper lip on the affected side.

50. It is common for the buccal nerve block to be routinely administered after IANB, even when buccal soft tissue anesthesia in the molar region is not required. There is absolutely no indication for this injection in such a situation The buccal nerve block, commonly, but incorrectly referred to as the long buccal nerve block, has a success rate approaching 100%. The reason for this is that the buccal nerve is readily accessible to the local anesthetic as it lies immediately beneath the mucous membrane, not buried within bone

51. REFERENCES Handbook of Local Anesthesia Stanley F Malamed 7 th Edition Mandibular canal variant: a case report Wadhwani, R. M. Mathur, M. Kohli, R. Sahu