DENTAL GROSS ANATOMY

CASE 4.1

(INFERIOR ALVEOLAR NERVE BLOCK)

HISTORY

A 23 yo man went to a dentist to have a mandibular 3rd molar extracted. The patient requested that plenty of anesthetic be given because he was extremely sensitive to pain. The dentist inserted the needle through the mucous membrane on the inside of the patient’s mouth, just lateral to the ridge produced by the underlying pterygomandibular raphe. After penetrating the adjacent muscle the tip of the needle came to rest near the lingula. In a few minutes the patient stated that his gum, lower lip, chin and tongue on the affected side were numb. During the extraction the patient said he felt pain; the dentist injected more anesthetic. The tooth was removed without further incident.

As the patient was leaving the dentist’s office he happened to look in a mirror and was surprised to find that he was unable to close his eye and that his mouth sagged on the affected side. He also noticed that his ear lobe was numb. The dentist explained that because of the large amount of anesthetic injected, other nerves in addition to those supplying the teeth had been anesthetized. He assured his patient that these effects would disappear in 3-4 hours.

1. Name the nerve supplying the mandibular 3rd molar tooth. What is this nerve a branch of (be specific)? In what region of the head does it arise?

NERVE SUPPLY OF THE TEETH

INFERIOR ALVEOLAR N.

V3 (POST. DIVISION)

2. The pterygomandibular raphe is used as a landmark when giving this type of nerve block. What is the pterygomandibular raphe and what are its bony attachments?

Superior pharyngeal constrictor m.

Pterygoid hamulus

Buccinator m.

Pterygomandibular raphe

Mandible

Pterygomandibular fold

Maxillary anterior teeth

Uvula

Dorsum of tongue

PTERYGOMANDIBULAR FOLD CAN BE SEEN AND PALPATED

3. What muscle was penetrated by the needle?

Buccinator m.

4. What is the lingula of the mandible? What fibrous structure attaches to it? What function does the lingula and the fibrous structure have when giving this type of nerve block?

LingulaMandibular foramen

Sphenomandibular lig.

5. Why was the patient’s chin and lower lip on the injected side also anesthetized?

Temporalis fascia and m.Anterior division (V3) (mostly motor)

Posterior division (V3) (mostly sensory)

Foramen ovale

Auriculotemporal n.

Inferior alveolar n. (cut)

Inferior alveolar n. (cut)

Lingual n.

Chorda tympani n.

Posterior andanterior deep temporal nn.

Masseteric n.

Lateral pterygoid n.and m.

Buccal n.

Mylohyoid m. (cut)

Digastric m. (anterior belly)

Mylohyoid n.

Mental n.

6. Why was the patient’s tongue on the injected side numb? Specifically, what part was affected? Were the tongue muscles paralyzed? Why or why not?

Temporalis fascia and m.Anterior division (V3) (mostly motor)

Posterior division (V3) (mostly sensory)

Foramen ovale

Auriculotemporal n.

Inferior alveolar n. (cut)

Inferior alveolar n. (cut)

Lingual n.

Chorda tympani n.

Posterior andanterior deep temporal nn.

Masseteric n.

Lateral pterygoid n.and m.

Buccal n.

Mylohyoid m. (cut)

Digastric m. (anterior belly)

Mylohyoid n.

Mental n.

INNERVATION OF TONGUE MUSCLES

XII

Hyoglossus m.

Genioglossus m.

Styloglossus m.

7. What is the relationship between the sensory nerve identified above (#6) and the mandibular 3rd molar? Is this nerve liable to be injured by the clumsy extraction of this tooth?

Lingual n.

3rd Molar

8. Describe the innervation of the gingiva of the mandibular teeth. In view of your answer, should the dentist have anesthetized any other nerve before performing this extraction?

INNERVATION OF TEETH & GINGIVAE

9. What caused the patient’s facial paralysis and loss of sensation in his ear lobule?

INFERIOR ALVEOLAR NERVE BLOCK

Pterygomandibular raphe

Lingual n.

Sphenomandibular ligament

Medial pterygoid m.Parotid gl.& facial n.

Inferior alveolar n.

Ramus of mandible

Temporalis m. insertion

Masseter m.

Buccinator m.

10. What complication might have arisen if the dentist had injected too far laterally? Too far medially? (Hint: what muscle might be pierced?)

INFERIOR ALVEOLAR NERVE BLOCK

Pterygomandibular raphe

Lingual n.

Sphenomandibular ligament

Medial pterygoid m.Parotid gl.& facial n.

Inferior alveolar n.

Ramus of mandible

Temporalis m. insertion

Masseter m.

Buccinator m.

END OF CASE 4.1