Background

An oral nerve block is a form of regional anesthesia used in dentistry to numb specific areas of mouth, allowing for pain-free dental procedures. During the procedure, the dentist or oral surgeon reviews the medical history of patient about potential allergies or reactions to anesthetics. A local anesthetic, which often includes a vasoconstrictor, is then injected near the target nerve, usually into the mucosa or adjacent tissue. The needle is carefully placed, and the anesthetic is administered using a precise technique. 

The effects of an oral nerve block are usually noticeable within minutes. The duration of numbness can vary based on the anesthetic used, the nerve targeted and the patient’s individual response. Benefits of an oral nerve block include effective pain relief, reduced discomfort, and precise anesthesia. However, there are some risks and complications to consider, such as temporary numbness, infection, hematoma, and potential nerve injury. Patients are generally advised to avoid eating or drinking until the numbness subsides to prevent accidental injury to their oral tissues. 

Indications

1. Tooth Extraction: to provide pain relief during the removal of a tooth, especially when dealing with molars or impacted teeth. 
2. Root Canal Therapy: To numb the affected tooth and surrounding areas for pain-free access to the root canal system. 
3. Dental restorations: For procedures such as fillings or crowns, particularly when working on posterior teeth where the procedure might be more involved. 
4. Oral surgery: for various surgical procedures including biopsies, soft tissue surgery, or treatment of oral lesions. 
5. Periodontal treatments: To manage pain during scaling and root planning, or other periodontal procedures involving deep cleaning and gum work. 
6. Endodontic procedures: To ensure comfort during treatments involving the pulp of the tooth, including complex root canal treatments. 
7. Implant placements: To numb the area where dental implants are being placed, ensuring that the patient remains comfortable throughout the procedure. 
8. Correction of malocclusion: In cases where orthodontic interventions require surgical adjustments or extractions. 

Contraindications

This procedure is contraindicated in the following: 

1. Hypersensitivity to local anesthetics 
2. Anatomical landmarks distortion: accurate identification of landmarks is crucial for performing the nerve block effectively 
3. Patient non-cooperation: Patients are anxious, have altered mental condition, or are otherwise uncooperative may require procedural sedation to ensure safety for both the clinician and patient. 
4. Injection through infected tissues: Anesthetics are less effective in infected tissue and may cause bacteremia or spread infection to nearby bone, tissues, or planes, making treatment difficult in such cases, only local or superficial anesthesia should be used. 
5. Cardiac conditions: Patients with cardiac disease, including congenital abnormalities, a history of cardiac surgeries, or cardiac disease, require prophylactic measures to prevent endocarditis. 
6.  Bleeding disorders: A history of coagulopathy or bleeding disorders must be considered to prevent complications. 
7. Preexisting neurologic damage: Document any existing neurologic damage thoroughly, however it should not prevent the clinician from proceeding with treatment. 

Outcomes

An oral nerve block offers various benefits, including effective pain relief, reduced procedural discomfort, enhanced patient cooperation, reduced need for systemic analgesics, improved healing and recovery, and reduced risk of complications. However, it also has temporary side effects like swelling and bruising, and can help diagnose the source of pain, aiding in the planning of further treatment. These outcomes depend on the specific clinical situation and patient response. 

Equipment

1. This includes: 
2. Needle, 1.5 to 2.0 inch, 25-27 gauge 
3. 4×4 gauze 
4. Aspirating dental syringe, or 3mL syringe 
5. Cotton-tipped applicators 
6. Nonsterile gloves 
7. Anesthesia (topical and local) 
8. Light source 
9. Yankauer suction catheter 
10. Suction source and tubing 
11. Any of the below mentioned antiseptic oral rinses 
12. Povidone- iodine (betadine) 
13. Hydrogen peroxide 
14. 0.5% chlorhexidine with 7% ethanol 
15. Chlorhexidine 0.12% 

Patient preparation

The oral nerve block procedure involves discussing the procedure, describing potential sensations, reviewing the patient’s medical history, and obtaining written consent. Pre-procedure instructions include fasting, avoiding alcohol and sedative, providing a comfortable setting, and positioning the patient in the dental chair. Local anesthesia preparation comprises of ensuring oral hygiene and disinfection of the area to be injected. The patient should be advised to avoid eating or drinking for 1 to 2 hours and to position their head comfortably in the dental chair. This ensures a safe and effective procedure. 

Patient positioning

An oral nerve block must be performed with the patient lying in supine position, reclined to approximately 75 degrees. A randomized study has shown that this supine position enhances the success rate for blocks in the first and second premolars compared to the upright position. However, no significant difference was found for blocks in the first molars, second molars, central or lateral incisors. For certain types of nerve blocks, different patient positions are recommended. For an inferior alveolar nerve block, the patient should be seated with their head resting against the headrest and the mandible parallel to the floor when open. For greater palatine and nasopalatine nerve blocks, a 45° neck extension is needed, which can be achieved by placing a rolled sheet beneath the patient’s shoulders. 

Technique

Approach considerations 

Before performing the procedure, obtain an informed consent and inject slowly to decrease pain. Use a 27 gauge needle for deep nerve block and avoid buffering with the bicarbonate. Apply pressure on the part adjacent to injection to divert the patient. Massage tissue for about 10 to 20 seconds to hasten the onset of local anesthetic. Achieving anesthesia with oral nerve blocks may take up to 10minutes. True allergies to local anesthetics are rare, but clinicians can differentiate between allergic reactions and adverse effects due to other factors. If the first attempt fails, try again. Some blocks like infraorbital and inferior alveolar, are best attempted after a skilled clinician has demonstrated them. 

Technical considerations

Supraperiosteal infiltrations 

This technique targets anesthetizing individual teeth like canines, premolars, and maxillary incisors. 

Landmarks: Locate the mucobuccal fold above the tooth to be anesthetized by using gauze to grasp the membrane and pulling it out and down for maxillary locations, or out and up for mandibular locations. 

Apply topical anesthetic. 

Approach: Insert the needle in o the mucobuccal fold with the bevel facing the bone, aligning it with the center of the tooth to be anesthetized and aiming toward the maxilla. Once maxilla is contacted, withdraw the needle 1mm. 

Aspirate and slowly inject 1 to 2 mL of local anesthetic at the apex of the root. 

ASA nerve block 

The ASA (anterior superior alveolar) nerve block provides anesthesia to the lateral and central incisors, maxillary canine, and the mucosa present on the top of these teeth. It may also occasionally affect the corresponding maxillary incisors. 

Landmarks: identify the mucobuccal fold at the point where it intersects with the apex of the canine tooth by retracting the membrane with gauze and pulling it out and down. 

Apply topical anesthetic. 

Aspirate and inject 2mL anesthesia slowly and gently massage the area for 10 to 20 seconds. 

Middle superior alveolar nerve block 

The MSA nerve block provides anesthesia to the maxillary premolars, with occasional coverage extending to the first molar and canine. 

Landmarks: identify the mucobuccal fold where it bisects with the junction of the second maxillary premolar and first molar. 

Apply topical anesthetic. 

Approach: While retracting the cheek, insert the needle at the intersection pint at 45°angle and advance it 1- 1.5cm. 

Aspirate and inject 2 to 3mL of local anesthesia slowly and gently massage the area for 10 to 20 seconds. 

Posterior superior alveolar nerve block 

The PSA nerve block provides anesthesia to the maxillary molar teeth. Note that the first molar might not be fully anesthetized with the PSA nerve block alone. In such cases, it can be combined with an MSA or supraperiosteal block for better coverage. 

Landmarks: Have the patients jaw opened partially and angled toward the operator. Retract the cheek laterally and identify the bisection of the mucobuccal fold with the connection of the first and second molars. 

Apply topical anesthetic. 

Approach: Insert the needle at the intersection and direct it toward the posterolateral maxillary tuberosity, aiming upward, inward, and backward along the curvature of the maxilla. Advance to a depth of approximately 2 to 2.5ccm. If the needle contacts bone, withdraw and slightly adjust the direction more laterally. 

Aspirate and inject 2 to 3mL of local anesthetic slowly. 

Infraorbital nerve block 

This anesthetizes the upper cheek, upper lip, nose and lower eyelid. The ASA nerve that supplies the maxillary canine, also branches from the maxillary nerve. Anesthetizing one nerve may result in overlapping anesthesia of the other. 

Nasopalatine nerve block 

This targets the anterior hard palate and related soft tissues. 

Inferior alveolar nerve block 

This provides anesthesia to all teeth on the same side of the mandible, as well as the chin and ipsilateral lip through the mental nerve.  

Landmarks: To perform the block, stand on the contralateral side of the target area, place thumb indie the patient’s mouth, and position index finger posteriorly and externally on the ramus. Ensure the patient’s jaw is open and align the syringe with the occlusal surfaces of the teeth. Insert the needle 1cm above the occlusal surface of the teeth, targeting the triangle at the ligula. Advance the until it makes contact with the bone, then withdraw it 1 to 2 mm. this technique usually anesthetizes the lingual nerve due to its proximity to the inferior alveolar nerve. 

A study by Saha et al. found that oral premedication with 10mg of KETO significantly increased the success rate of inferior alveolar nerve blocks in patients with irreversible pulpitis. 

Mental nerve block 

This targets the skin of the chin and the ipsilateral lower lip. 

Landmarks: To identify the mental foramen, retract the lip and cheek, and find out the junction between the 1st and 2nd mandibular premolars, then move 1cm inferior to the gum line, just medial to the midline pupil. This location aligns with the infraorbital foramen. 

Preparation: Apply a topical anesthetic. 

Approach: Insert the needle 1cm below the second premolar at a 45° angle. Advance the needle until it contacts the mandible, then withdraw slightly. 

Aspirate and inject 1 to 2ml of local anesthetic near the foramen and gently massage the area for 10 to 20 seconds. 

Lingual nerve block 

This targets the anterior two-thirds of the tongue. It also carries the chorda tympani from the facial nerve, which provides taste sensation to the anterior two-thirds of the tongue, and trasnits preganglionic fibers from the chorda tympani to the submandibular ganglion, influencing the sublingual and submandibular glands. 

Landmarks: Lingual nerve is present on the lingual aspect of 2nd mandibular molar. 

Preparation: Apply a topical anesthetic. 

Approach: Position on the contralateral side. Using a tongue blade, lift the tongue and iinsert the needle 1cm below the gumline of the second mandibular molar. Advance the needle posteriorly by 1cm. 

Aspirate and inject 1 to 1.5ml of local anesthetic. 

Buccal nerve block 

The buccal nerve targets the mucous membrane of the vestibule and cheek and a small area of facial skin slightly. 

Landmarks:  identify the buccal nerve 1mm lateral to the third mandibular molar, at the anterior border of the ramus, in alignment with thee occlusal plane. 

Preparation: Apply a topical anesthetic. 

Approach: Using thumb of non-dominant hand, retract the cheek laterally. Insert the needle into the anterior border of the ramus, 1mm lateral to the third mandibular molar, and align it with the occlusal plane. Advance the needle 3 to 4 mm. 

Aspirate and slowly inject 2mL of local anesthetic. 

Complications

If an injection is done far away into the parotid gland it can cause anesthesia and transient Bell palsy. Treatment involves eye protection until the anesthetic clears off. For avoiding this complication, ensure that the needle contacts the mandible/bone before injection. Transient facial nerve palsy can be restored within 5 hours after an inferior alveolar nerve block. 

References

Oral Nerve Blocks — NUEM Blog 

References

Oral Nerve Blocks — NUEM Blog