Administering local anesthetics effectively is a critical skill in dentistry, as it ensures patient comfort and procedural success. The goal of any injection is to deliver the anesthetic to the appropriate nerve or tissue while minimizing discomfort and maximizing efficacy.

Infiltration injections are used to anesthetize a small, localized area, typically a single tooth and its surrounding soft tissue. This technique is most effective in the maxilla due to the thin cortical bone, which allows the anesthetic to diffuse easily to the nerve endings. For example, a local infiltration near the apex of a maxillary central incisor can provide profound anesthesia for restorative work on that tooth.

Nerve blocks target larger areas by anesthetizing the main nerve trunk before it branches into smaller nerves. These injections are commonly used in the mandible, where the dense cortical bone makes infiltration less effective. Examples include the inferior alveolar nerve block (IAN block), which anesthetizes all mandibular teeth in one quadrant, and the posterior superior alveolar (PSA) block, which anesthetizes the maxillary molars.

Successful administration of local anesthetics requires a thorough understanding of anatomical landmarks. Below are some of the most commonly used injections and their associated landmarks.

Inferior Alveolar Nerve (IAN) Block is used to anesthetize all mandibular teeth in one quadrant, as well as the buccal soft tissue anterior to the molars.

• Landmarks: 

• • The coronoid notch, the deepest concavity on the anterior border of the mandibular ramus.
  • The pterygomandibular raphe, a fibrous band of tissue that serves as a guide for needle insertion.
  • The mandibular occlusal plane, which helps determine the height of the injection.

• Technique: 

• • The needle is inserted approximately 1.5 cm above the occlusal plane, lateral to the pterygomandibular raphe.
  • Advance the needle until bone is contacted (usually 20-25 mm deep), withdraw slightly, aspirate to ensure the needle is not in a blood vessel, and inject slowly.

Posterior Superior Alveolar (PSA) Block is used to anesthetize the maxillary molars, except for the mesiobuccal root of the first molar in some cases.

• Landmarks: 

• • The zygomatic process of the maxilla.
  • The mucobuccal fold above the maxillary second molar.

• Technique:

• • The needle is inserted at a 45-degree angle to the occlusal plane and advanced approximately 16 mm into the tissue.
  • Aspiration is critical to avoid injecting into the pterygoid venous plexus, which can lead to a hematoma.

Mental Nerve Block is used to anesthetize the buccal soft tissue from the mandibular premolars to the midline.

• Landmarks: 

• • The mental foramen, located near the apices of the mandibular premolars.
  • Technique:
  • Palpate the mental foramen and insert the needle anterior to it. Aspirate and inject slowly.

Greater Palatine Nerve Block is used to anesthetize the posterior hard palate from the maxillary third molar to the first premolar.

• Landmarks: 

• • The greater palatine foramen, located near the junction of the maxillary alveolar process and the hard palate, typically opposite the second molar.

• Technique:

• • Apply pressure with a cotton tip applicator to the foramen before injecting to minimize discomfort.

Nasopalatine Nerve Block is used to anesthetize the anterior hard palate from canine to canine.

• Landmarks:

• • The incisive papilla, located at the midline of the palate behind the maxillary central incisors.

• Technique:

• • Insert the needle at the base of the incisive papilla and inject slowly.

Canine (Infraorbital) Block is used to anesthetize the maxillary central and lateral incisors, canines, and sometimes the premolars, along with their associated buccal soft tissues.

• Landmarks:

• • The infraorbital foramen, located below the orbit and above the maxillary first premolar.
  • The mucobuccal fold at the level of the first premolar.

• Technique:

• • Palpate the infraorbital foramen to locate its position.
  • Insert the needle into the mucobuccal fold over the maxillary first premolar. Angle the needle toward the infraorbital foramen and advance it approximately 16 mm.
  • Aspirate and inject slowly.

Gow-Gates nerve block is used to anesthetize the mandibular nerve and its branches, providing profound and widespread anesthesia to the mandibular quadrant. Unlike the inferior alveolar nerve (IAN) block, which is limited in scope and has a higher failure rate, the Gow-Gates technique is designed to deliver anesthesia to a larger area, including the inferior alveolar nerve, lingual nerve, buccal nerve, mylohyoid nerve, auriculotemporal nerve, and mental nerve. 

• Landmarks

• • Tragus of the Ear: Serves as a reference for the posterior positioning of the condyle.
  • Corner of the Mouth: The syringe is aligned from the contralateral corner of the mouth for proper angulation.
  • Neck of the Mandibular Condyle: The target area, where the mandibular nerve exits the foramen ovale after branching from the trigeminal nerve (V3).
  • Intertragic Notch: Used for vertical alignment of the syringe.

• Technique

• • Patients must open their mouths wide to fully translate the mandibular condyle forward. This movement creates better access to the target area.
  • The injection is administered at the height of the mesiolingual cusp of the maxillary second molar. The needle passes through the buccal mucosa and soft tissues to reach the neck of the condyle.
  • Insert the needle at the height of the mesiolingual cusp of the maxillary second molar, directing it toward the neck of the condyle.
  • The syringe should be aligned parallel to an imaginary line between the corner of the patient’s mouth and the intertragic notch of the ear.
  • Advance the needle slowly until it contacts bone at the condylar neck (approximately 25 mm deep for most patients).
  • Once bone is contacted, withdraw the needle slightly (1-2 mm) to avoid injecting into the periosteum.
  • Aspiration is crucial to avoid intravascular injection, as the pterygoid venous plexus is in close proximity.

Even with proper technique, complications can arise during or after the administration of local anesthetics. These may include

• Pain During Injection – caused by rapid injection, poor technique, or failure to use a topical anesthetic. Always inject slowly (1 cartridge per minute) and use a topical anesthetic to numb the surface tissue before needle insertion.

• Hematoma Formation – caused by accidental puncture of a blood vessel, particularly during PSA or IAN blocks. Apply pressure and ice to the area immediately. Avoid further injections in the same site until the hematoma resolves.

• Trismus – caused by trauma to the muscles of mastication or the temporomandibular joint during injection. Advise the patient to apply warm compresses and perform gentle jaw exercises.

• Paresthesia – caused by trauma to the nerve during injection or contamination of the anesthetic solution. Reassure the patient that most cases resolve spontaneously within a few weeks. If symptoms persist, refer to a specialist.

• Inadequate Anesthesia – caused by incorrect needle placement, insufficient anesthetic volume, or anatomical variations. Reassess landmarks and technique, and consider using a supplemental injection, such as a periodontal ligament (PDL) injection.