Mandibular Nerve & Inferior Alveolar Nerve Block PDF

Mandibular Nerve (V3)  largest division of trigeminal nerve & the only mixed  Has large sensory root & small motor root Course of the nerve:  In foramen ovale, both sensory & motor roots join, to form the nerve trunk a. Nervus spinosus (sensory): arises outs...

Mandibular Nerve (V3)  largest division of trigeminal nerve & the only mixed  Has large sensory root & small motor root Course of the nerve:  In foramen ovale, both sensory & motor roots join, to form the nerve trunk a. Nervus spinosus (sensory): arises outside  then leave the skull to enter the infratemporal fossa the skull & re-enters the skull through  After leaving the skull, the mandibular trunk suspends foramen spinosum to supply mastoid air cells the otic ganglion & the trunk gives 2 branches: & dura matter of middle cranial fossa b. Nerve to medial pterygoid (motor) : supplies medial pterygoid, tensor palati, & tensor tympani muscles  o The nerve trunk is very short & divides 2-3mm below the foramen into small anterior division & large posterior division: A. Branches of anterior division (three motors & one sensory) Three motors One sensory 1. Nerve to temporalis o Long buccal nerve crosses the anterior 2. Nerve to Masseter border of ramus to supply: 3. Nerve to lateral pterygoid o Skin of the cheek o Buccal mucoperiosteum of lower molars & mucobuccal fold in that region  B. Branches of posterior division: (three sensory and one motor) 1. Auriculotemporal nerve: Arises by 2 roots, surrounding the middle It gives the followings: meningeal artery, & passes deep to the a. Branches to external auditory meatus to innervate skin over condylar neck meatus & tympanic membrane then runs upwards behind the condyle, b. Articular branch to TMJ crossing the root of zygomatic arch in c. Temporal branch to supply the skin over temporal area company with the superficial temporal d. Auricular branch to supply skin over helix and tragus artery e. Communicates with Otic ganglion to provide parasympathetic secretory fibers to parotid gland 2. Lingual nerve Runs in infratemporal fossa, then submandibular region I. In the infratemporal fossa: the lingual nerve II. In submandibular region: joins chorda tympani (branch of facial nerve), a.Lingual n. lies in pterygomandibular space which carries the following fibers: (between ramus & medial pterygoid m.) a. Taste fibers: to anterior 2/3 of tongue i. It runs 1 cm anterior, medial, & parallel to b. Parasympathetic secretory fibers to IAN submandibular & sublingual SG ii.Then, descends to cross the posterior end of mylohyoid line just behind & medial to the socket of 3rd molar to pass on the superficial surface of the hyoglossus muscle b. Then, the nerve hooks around the submandibular duct 3. Inferior alveolar nerve (IAN): (Wharton’s) to be medial to it o It lies posterior & lateral to lingual n. c. Both structures pass forwards to reach the tongue o In the region between sphenomandibular ligament & medial surface of ramus; IAN enters the mandibular d. Submandibular ganglion is suspended from lingual n. foramen to run in mandibular canal The lingual nerve supplies: o It is accompanied by inferior alveolar vessels i. Lingual mucoperiosteum of all lower teeth ii. Floor of the mouth iii.Mucous membrane of anterior 2/3 of tongue with taste (via chorda tympani) & general sensations iv. Carries parasympathetic secretory fibers to sublingual & submandibular SG through chorda tympani  IAN gives the following branches 1. Mylohyoid nerve (mixed n.): prior to entry of IAN into mandibular 2. Branches to all mandibular teeth canal, it gives mylohyoid n. that descends in mylohyoid groove & 3. Terminal branches: supplies: a. Mental nerve that emerges through oMylohyoid & anterior belly of digastric muscles (motor supply) mental foramen to supply skin over oSkin over the mental protuberance (sensory) chin, lower lip & buccal muco- oIn some people: mylohyoid n. gives extra pulpal innervation to lower periosteum of premolar region molars b. Incisive nerve continues inside the mandible to supply the anterior teeth  Innervation of Teeth Maxillary teeth Mandibular teeth Upper teeth Pulp, bone, Buccal Palatal Tooth Pulp, bone Buccal Lingual mucoperiosteum Mucoperiosteum Mucoperiosteum Mucoperiosteum 1, 2,3 ASA nerve Nasopalatine n. 1,2,3 Incisive n Incisive n Lingual 4,5, MB of 6 MSA nerve Greater palatine n 4,5 IAN Mental n nerve 6,7,8 PSA nerve 6,7,8 IAN Long buccal n  Accessory innervation (additional Nerve Supply in some patients) 1. Labial mucoperiosteum of upper & lower centrals 2. Buccal mucoperiosteum of lower premolars: a. May receive additional supply from the other side a. Cutaneous coli nerve is a branch from cervical where some fibers may cross the midline plexus of nerves (C2 & C3 are spinal nerves) b. Discovered if you give nerve block anesthesia. But that extend to the buccal mucoperiosteum of with infiltration, the patient does not feel pain) lower premolars b. Patients fells pain despite of IANB is working. c. The pain is blocked with buccal infiltration in the region of lower premolars 3. Pulp of lower 6,7,8 Sensory fibers from mylohyoid nerve may supply pulp of lower molars that may also reach anterior teeth. It can be blocked by lingual infiltration 4. Bifid inferior alveolar There are 2 inferior alveolar nerves. One of them enters the mandible through foramina in the retromolar area. They supply pulp of lower 8 and blocked by infiltration  Mandibular Anesthetic techniques  more difficult than maxillary techniques, because: a.Greater anatomic variation in the mandible b. the need for deeper soft tissue penetration  Infiltration techniques are used to: a. Anesthetize lower anterior teeth as surrounded by thin cortical bone that enables LA to b. All mandibular teeth of children diffuse into bone Lower posterior teeth of adults are anesthetized by nerve block, because IAN is in a canal that surrounded by dense cortical bone For lower anterior teeth, 2 nerves are anesthetized: For lower molars, 3 nerves are anesthetized: a. Incisive nerve (branch of IAN): supplies pulp, bone, & a. IAN: supplies pulp & bone labial mucoperiosteum b. Long buccal n. : supplies buccal mucoperiosteum b. Lingual nerve: supplies lingual mucoperiosteum c. Lingual nerve: supplies lingual mucoperiosteum For lower premolars, following nerves are anesthetized a. IAN: supplies pulp & bone Note Lingual nerve & IAN are anesthetized by the b. Mental nerve supplies buccal mucoperiosteum same nerve block technique (through one injection) c. Lingual nerve supplies lingual mucoperiosteum  Types of anesthetic block techniques 1. IAN and lingual nerve are anesthetized by 3. Incisive nerve is anesthetized by Incisive nerve  IAN block block that provides anesthesia to pulp and labial  Vazirani-Akinosi mandibular nerve block soft tissue (not lingual) of anterior teeth  Gow-Gates nerve block 4. Long buccal nerve is anesthetized by long buccal 2. Mental nerve is anesthetized by: Mental nerve infiltration, long buccal nerve block, or Gow-Gates block, providing anesthesia to buccal soft tissue of nerve block, providing anesthesia to the buccal premolar area only mucoperiosteum of the lower molars  Applied anatomy and inferior alveolar nerve block 1. Pterygomandibular space 2 major intraoral structures is considered in IANB 2. Mandibular foramen site 1. Pterygomandibular space: (into which needle is inserted) Anteriorly: - Structures in pterygomandibular space have significant 1. Buccinator & superior constrictor muscles impact on the IANB's effectiveness & safety form a fibrous junction - It is a small cleft between medial pterygoid (medially) & 2. Pterygomandibular raphe (ligament) attached medial surface of ramus (laterally) superiorly to pterygoid hamulus of the medial - Parotid gland presents posteriorly pterygoid plate, & inferiorly to the posterior end of the mylohyoid ridge The pterygomandibular space contains: a) IAN, artery, and vein b) Lingual nerve c) Nerve to mylohyoid d) Sphenomandibular ligament: IAN is located lateral to it (spine of sphenoid to ligula) Note When the needle enters the pterygomandibular Mandibular foramen: space through buccinator muscle, the needle is o Located halfway between superior & inferior directed just superior to the lingula borders of mandible  IAN, artery, and vein are wrapped together by o 2/3– 3/4 the distance from anterior border of fibrous sheath (neurovascular bundle), before ramus to its posterior border entering the inferior dental canal. The lingual nerve o Its height varies, ranging from 1-19 mm above the is located 1 cm anterior and medial to the IAN occlusal plane Mandibular Techniques Inferior alveolar nerve block Areas Anesthetized Other names: mandibular block (inaccurate name) 1. Mandibular teeth to the midline Nerves Anesthetized: 2. Body of mandible and inferior portion of ramus 1. IAN & its terminal branches (Incisive and Mental) 3. Buccal mucoperiosteum anterior to the mental foramen (mental nerve) 2. Lingual nerve 4. Anterior 2/3 of tongue & floor of mouth (lingual nerve) 5. Lingual mucoperiosteum of all lower teeth (lingual n) 6. Lower lip & chin on the injected side (mental)  Disadvantages: Indications: ◦ High failure rate (31-81%) 1. Dental procedures on multiple mandibular teeth in one ◦ Intraoral landmarks not always reliable quadrant ◦ Positive aspiration (10-15%), the highest of all 2. When buccal soft tissue anesthesia (anterior to the intraoral techniques) mental foramen) is required ◦ Lingual & lower lip anesthesia, uncomfortable for 3. When lingual soft tissue anesthesia is needed many patients causing self-inflicted soft tissue trauma Contraindications: especially in children Infection or acute inflammation at injection site (rare) ◦ Possible partial anesthesia in the following cases: - Presence of bifid IAN and bifid mandibular canals Advantages: One injection provides a wide area of anesthesia - Cross-innervation in the lower anterior region Needle: A 25- gauge long needle Area of insertion: Mucous membrane on medial (lingual) side of ramus Target area: IAN before it enters the mandibular foramen Landmarks: 1. Coronoid notch (greatest concavity on anterior border of ramus) 2. Pterygomandibular raphe 3. Occlusal plane of lower posterior teeth Bone contact with needle insertion: The needle penetration depth to bone contact is 20 - 25 mm (2/3-3/4 the length of long dental needle) Patient position Operator position: According to the working side:  Semi-supine or supine (to avoid patient A. The right side of the patient fainting), but never in an upright position 1. The operator stands in front of the patient (8 o’clock) The mouth should be opened wide, to improve 2. The operator’s left index finger is used for palpation visibility and accessibility to injection site of coronoid notch, external & internal oblique ridge of the right side B. The left side: there are 3 options i. Cross hand technique: the operator & chair iii. Behind (indirect) technique: (most popular) the positions are the same as above. The left index operator stands behind & on the right side of the finger is used for intraoral palpation & the right patient (10 o’clock) & the back of chair is semi-supine (or almost supine), & the patient is asked to extend & hand is used for LA injection, but both hands turn his head towards the operator. The left thumb are crossed together finger is used for palpation ii. Left hand technique: the operator uses the right index finger for palpation of landmarks, while left hand is used for injection  Left-handed operator Must follow the same rules, but for the opposite side of the right-handed operator (the previous 3 options are used for anesthetization of the right IANB) For the left side of the patient, the operator stands in front of the patient at 8 o’clock  1. Pterygomandibular raphe: (seen) Procedure - Bounds the area medially Retro-molar area, which is distal to lower 8, should be palpated - Extends from posterior end of maxilla to first. The site of lower 8 must be considered if it is extracted or the lower ridge doesn’t erupt. - Its lower end determines the beginning of This area is bounded by 3 structures that must be determined the retro-molar area for successful IANB. - Injection site is lateral to it Two of them are palpated and one is seen in the oral cavity Medial injection leads to: 1- Pterygomandibular raphe: (seen) a. Failure of IANB b. Causes pharyngeal anesthesia, resulting in a sensation of 2- Deepest portion of the external oblique ridge (EOR, palpable) suffocation (although this is not a real suffocation). However, 2- Internal oblique ridge (IOR, palpable) you must confirm that there is no respiratory distress 2. Deepest portion of external oblique ridge 3. Internal oblique ridge (IOR, palpable): (EOR, palpable):  Located medial to EOR, on medial surface of ramus EOR is the anterior border of the ramus that extends  Line connecting the deepest part of EOR, IOR, & lingula), runs // to lower occlusal plane over mandibular foramen from the coronoid process to the lower 7, 8  Lingula lies 10-11mm posterior to IOR (over mandibular Palpate its deepest part, as it determines the height foramen) of injection  Injection site is midway (5mm) between IOR & lingula at the height and midpoint of the operator’s finger that palpates these structures  Steps 1. The patient open his mouth widely, to locate the raphe 2. Palpate the deepest area of EOR using index finger on the right side & thumb finger on left side 3. Finger is moved from molar area (vestibule) up to coronoid with the nail is directed upward to feel the deepest area EOR= external oblique ridge (deepest area) 4. Once this deepest area has been palpated, keep your finger IOR= Internal oblique ridge, L at this height because this is the height of injection, which is = lingula, CN = coronoid notch 6-10mm above the occlusal plan PMR = pterygomandibular raphe H = pterygoid hamulus 5. Then rotate the finger (with its nail pointing towards 7. Finger is used to stretch the tissues laterally: midline) medially across the retro-molar area to a. Allowing better visibility at injection site palpate the IOR b. Making needle insertion less painful 6. Do not insert the needle unless you palpate the IOR 7. Once you locate the IOR at the height of the deepest area of EOR, retract the finger slightly laterally so that only finger’s tip is contacting the IOR (i.e., the first phalange of the finger is not placed on the IOR) 8. The finger must be // to the lower occlusal plane 8. Maintain the finger position, do not move it while preparing the tissues 9. Distance between fingertip midpoint & insertion point is 5mm 10. Syringe's barrel is inserted from premolar area of the opposite side (at corner of the mouth) & rests on the lower second premolar’s occlusal plane 11. The needle will be 6-10mm above occlusal plane when syringe is rested on it 12. For the block technique to be successful, the needle must be in contact with bone 13. You must imagine where the ramus is located & know that the ridge and ramus are not in the same plane. Therefore, the needle should be inserted perpendicular to the ramus rather than parallel to it 14. Advance needle into the tissues until it contacts bone at depth: 20-25mm Safety Features: The needle must 15. Aspirate in 2 planes, if –ve, slowly inject 2/3 of the cartridge contact bone, to prevent needle 16. To anesthetize the lingual nerve, withdraw the needle 1cm then re-inject over-insertion with its associated the remaining 1/3 of solution complications. Do not advance the 17. Withdraw the syringe slowly and make the needle safe needle more than 25mm 18. After 20 seconds, return the patient to the upright or semi supine position 19. Wait 3 - 5 minutes before testing anesthesia Signs and Symptoms Complications Subjective: 1. Hematoma (rare): swelling of tissues on medial 1. Tingling, numbness, or swelling of lower lip indicates side of ramus. Managed by applying pressure & anesthesia of mental nerve. Although it is a reliable ice application to the area for at least 3-5 minutes indicator that IAN is anesthetized, it is not accurate 2. Trismus: limited jaw movement due to muscle indicator of anesthetic depth (potency) spasm 2. Tingling or numbness of the tongue indicates a. Slight degree of soreness when opening the anesthesia of lingual nerve mandible is common after IANB (occurs after LA Objective: No pain is felt during probing fades off) b. Severe pain associated with limited mandibular opening is uncommon 3. Transient facial paralysis: a. The facial nerve (motor nerve to facial expression muscles) is blocked when LA is deposited into posterior lobe of parotid b. Signs and symptoms: o The inability to: Close the eye, raise the eyebrow, blow the check o Drooping of the upper lip on the affected side o Deviation to the other side  2. Low injection: needle directed downward; this leads Injection errors to trismus due to injection into medial pterygoid and 1. High injection: toxicity due to injection into the posterior facial vein Syringe barrel or needle are directed upward leading to: 3. Early touch: a. Ear numbness due to injection near auriculotemporal  The needle is inserted more laterally (anteriorly) on nerve the ramus b. Trismus due to injection into lateral pterygoid c. Toxicity due to injection into pterygoid plexus of veins  The distance between the finger and the site of insertion is less than 5mm  To correct: insert the needle from more anterior position 4. No bony contact: There are 2 possibilities for no bony contact The distance is > 5mm, & needle isn’t perpendicular to ramus (20mm): There is a great possibility to deposit LA into posterior lobe of i. No bony contact, but lateral to parotid. So, if there is no touch bone never go into tissues sphenomandibular ligament, allowing solution to more than 20-25mm diffuse to nerve causing anesthesia (not potent) To correct: insert the needle from more posterior position ii. No bony contact, but its medial to sphenomandibular ligament, the anesthesia fails to diffuse where the ligament acts as a barrier resulting in failure of LA