Dentistry 2: Nerve Blocks and Oral Tumors

Benefits of Local Anesthesia

• Nerve cells send small electrical currents through adjacent nerve cells.
• Currents arise from the exchange of sodium and potassium ions.
• Local anesthetics block sodium ion channels, preventing nerve cell entry.
• Bupivicaine 0.5% offers a duration of 4-10 hours with an 8-30 minute onset.
• Lidocaine 2% provides 60-120 minutes of anesthesia, with a 5-minute onset.
• Combining bupivicaine and lidocaine can interfere with each drug's mechanism of action, canceling them out.
• Toxicity and adverse reactions may include anaphylactic reactions, skeletal muscle toxicity, and permanent nerve damage.
• A general guideline to avoid toxicity is a maximum dose of 2mL/kg per patient.
• The appropriate amount per site is at the practitioner's discretion.
• Use 0.1mL for cats and small dogs.
• Administer 0.2mL for medium dogs.
• Use 0.3mL for large dogs.

General Techniques for Nerve Blocks

• Employ a 25g needle and a 1mL syringe.
• Ensure the needle placement avoids trauma to the nerve and penetration of a blood vessel.
• Regularly aspirate when placing the needle to prevent injecting into a blood vessel.
• Ensure atraumatic entry into the foramen.
• Apply pressure over the foramen to maintain anesthetic localization.

The Foramen & The Blocks

• The infraorbital foramen is accessed via a rostral block.
• The inferior alveolar foramen requires a caudal mandibular block.
• The middle mental foramen (uncommon) uses a rostral mandibular block.
• A caudal maxillary block exists.

Infraorbital Foramen Block

• This is a rostral approach.
• It effectively blocks the maxillary 3rd premolar and all teeth mesial of it on the same side.
• Achieve comprehensive blockade of all maxillary teeth on one side, adjacent bone, and soft tissue by advancing the needle deep into the foramen and maintaining the local anesthetic within the foramen.
• Apply firm pressure to the foramen for 60 seconds and tilt the nose skyward for optimal effect.
• The anatomical landmark for this block is the mesial root of the 3rd premolar.

Caudal Maxillary Block

• Branches of the maxillary nerve, infraorbital nerve, pterygopalatine nerve, and major/minor palatine nerve are affected by this block.
• It encompasses bones, teeth, and soft tissues of the upper jaw, including the bones of the hard palate, and mucosa of the hard and soft palate on the corresponding side.
• Advance the needle only 3-5 mm to avoid the eye.

Middle Mental Foramen

• This block is not commonly used
• In dogs, a dental nerve block impacts the incisors and canine tooth on the corresponding side, along with adjacent bone and soft tissue.
• Landmark identification and foramen entry pose significant challenges.

Inferior Alveolar Nerve Block

• This block affects all mandibular teeth, mandibular bone, and soft tissue on the corresponding side rostral to the injection site.
• Palpate for the facial vascular notch; insert the needle underneath on the inside of the mandible; draw back and inject, it is important to hit bone before locating the foramen.

Oral Tumors

• Malignant tumors can spread to distant sites.
• Benign tumors remain localized.
• Tumors can exhibit metastatic behavior.
• Excision may be curative.
• Histopathology is the gold standard for diagnosis.
• Regional lymph node biopsies can provide additional diagnostic information.

Step 1 - Recognizing Normal

• Recognizing normal anatomy is crucial.
• Bilateral lesions are often anatomical; not pathological.

Step 2 - What to know

• A detailed lesion location and measurements are crucial.
• Create a charting code = OM/
• Radiographs may be needed to assess bone involvement & other diseases.

Melanoma (MM)

• Melanoma is the most prevalent oral cancer in dogs, though rare in cats.
• Melanoma can occur anywhere in the oral cavity
• High rates of metastasis to lungs, lymph nodes, and bone are common.
• The prognosis for melanoma is generally poor, with a high recurrence rate.

Squamous Cell Carcinoma (SCC)

• This is #1 in cats, #2 in dogs for most common oral cancers.
• Squamous Cell Carcinoma can occur anywhere in the oral cavity
• This will invade the bone cavity.
• The further the tumor from the tonsils, the better the prognosis.
• Secondhand smoke exposure is a significant risk factor.

Lecture about nerve blocks and oral tumors, including the benefits of anesthesia and general techniques for nerve blocks. It covers onset times, maximum does, and toxicity.