Comprehensive Notes on Maxillary and Mandibular Nerve Supply and Anatomy

The Nerve Supply of the Maxilla and Mandible

Chairside Support During Oral Health Assessment (Unit Code H4PW 04)

Role and Responsibilities: This standard is designed for individuals providing chairside support during the assessment of a patient's oral and general health.
Preparation: You are responsible for preparing all necessary equipment, instruments, materials, and medicaments for the assessment.
Direct Support: Provide close support during the patient assessment by:
- Recording and charting information obtained from an examination of the head, neck, teeth, periodontium, and soft tissues.
- Interpreting or anticipating the need for additional equipment, instruments, materials, and medicaments.
Essential Components:
- Effective communication with patients and other members of the oral healthcare team.
- Promoting the health, safety, and well-being of the patient.
Applicability: This standard applies to oral health workers in a chairside support role during oral and general health assessments.
Practice Updates: Users must ensure that their practice reflects up-to-date information and policies.

Bone Structures of the Maxilla and Mandible

Key Bones Related to Oral Cavity and Head:
- Maxilla: The upper jaw.
- Mandible: The lower jaw.
- Zygoma: Cheekbone.
- Temporal Bone: Bone forming part of the side and base of the skull, articulating with the mandible at the TMJ.
- Frontal Bone: Bone forming the forehead.
- Nasal Bone: Bone forming the bridge of the nose.
- Sphenoid Bone: A complex bone at the base of the skull anterior to the temporal bone.
- Parietal Bone: Bones forming the top and sides of the skull.
- Occipital Bone: Bone forming the back and base of the skull.
Anatomical Features of the Mandible:
- Condyle: The rounded projection that articulates with the temporal bone at the TMJ.
- Coronoid Process: A triangular projection on the anterior part of the ramus.
- Sigmoid Notch (Mandibular Notch): The indentation between the condyle and the coronoid process.
- Alveolar Process: The part of the mandible containing the tooth sockets.
- Body: The horizontal part of the mandible.
- Ramus: The vertical part of the mandible, extending upwards from the posterior body.
- Angle: The junction between the body and the ramus.

The Foramen (Foramina) of the Maxilla and Mandible

Mandibular Foramen: Located on the medial surface of the mandibular ramus. It is an opening for the inferior alveolar nerve and vessels.
- Lingula: A small tongue-shaped projection of bone located on the medial aspect of the mandibular foramen, serving as an attachment point.
Mental Foramen: Located on the external surface of the mandible, below the apices of the premolars. It transmits the mental nerve and vessels.
Incisive Foramen: Located on the midline of the hard palate, posterior to the maxillary central incisors. It transmits the nasopalatine nerve and vessels.
Greater Palatine Foramen: Located on the posterior lateral aspect of the hard palate, bilaterally. It transmits the greater palatine nerve and vessels.
Lesser Palatine Foramen: Typically posterior to the greater palatine foramen, transmitting lesser palatine nerves and vessels.

Temporomandibular Joint (TMJ)

Components:
- Condyle: Of the mandible.
- Temporal Bone: Specifically the Glenoid Fossa (or Mandibular Fossa).
- Articular Disc (Meniscus): A biconcave fibrous disc located between the condyle and the glenoid fossa, allowing smooth movement and absorbing stress.
Function Basic Premises:
- When the mandible closes, there is an ideal way for the teeth to contact.
- There is an ideal place for the condyle and disc to be situated within the glenoid fossa.
Associated Muscle: Lateral pterygoid muscle of mastication (attaches to the articular disc and condyle).
Conditions:
- Subluxation: Often referred to as "lock jaw," this is partial dislocation where the articular surfaces remain in partial contact. The disc and condyle may get caught, but the jaw can often be re-positioned by the patient.
- Dislocation: Complete displacement of the condyle from the glenoid fossa, where the articular surfaces are no longer in contact. This usually requires manual reduction by a professional.

Nerve Supply to the Oral Cavity (General Principles)

Origin of Nerves:
- All nerves supplying the oral cavity run directly from the brain as cranial nerves.
- Nerves for the rest of the body run from the spinal cord as systemic nerves.
Cranial Nerve Types: Cranial nerves can be:
- Sensory: Convey pain or other sensations (e.g., touch, temperature, taste).
- Motor: Make muscles and glands work (control movements and actions).
- Combination of both (Mixed): Possess both sensory and motor functions.
Number of Cranial Nerves: There are $12$ pairs of cranial nerves that leave the brain.
Dental Relevance: Four pairs of cranial nerves are particularly relevant to dentistry.

Specific Cranial Nerves Relevant to Dentistry

Trigeminal Nerve ( $5^{th}$ Cranial Nerve)

Primary Supply:
- Teeth
- Soft tissues of the oral cavity (e.g., gingivae, oral mucosa)
- Muscles of mastication (chewing)
Divisions: The trigeminal nerve divides into three main branches:
1. Ophthalmic Branch (V1):
  - Type: Sensory nerve.
  - Supply: Soft tissue around the eye and upper face.
  - Pathway: Exits the cranium through the superior orbital fissure.
2. Maxillary Branch (V2):
  - Type: Sensory nerve.
  - Supply: Upper teeth, maxilla, and upper area of the face.
  - Pathway: Exits the cranium through the foramen rotundum.
  - Buccal Divisions (Superior Alveolar Nerves): Supply buccal (cheek side) gingivae and upper teeth.
    - Anterior Superior Alveolar Nerve:
      - Supply: Maxillary incisors ( $1, 2$ ), canines ( $3$ ), and their associated labial (lip side) gingivae. Also, soft tissues of the upper lip and nostrils.
    - Middle Superior Alveolar Nerve:
      - Supply: Maxillary premolars ( $4, 5$ ), the mesial half of the first molar ( $6M$ ), and their associated buccal gingivae.
    - Posterior Superior Alveolar Nerve:
      - Supply: The distal half of the first molar ( $6D$ ), second molar ( $7$ ), third molar ( $8$ ), and their associated buccal gingivae.
  - Palatal Divisions: Supply palatal (tongue side) gingivae.
    - Nasopalatine Nerve:
      - Supply: Palatal gingivae of the upper central incisors ( $1$ ), lateral incisors ( $2$ ), and anterior half of the canines ( $3$ ).
      - Entry Point: Enters the oral cavity via the incisive foramen.
    - Greater Palatine Nerve:
      - Supply: Palatal gingivae of the molars ( $6, 7, 8$ ), premolars ( $4, 5$ ), and the posterior half of the canines ( $3$ ).
      - Entry Point: Enters the oral cavity via the greater palatine foramen.
3. Mandibular Branch (V3):
  - Type: Both sensory and motor nerve.
  - Supply (Sensory): Lower teeth, mandible, lower face.
  - Supply (Motor): Muscles of mastication.
  - Pathway: Exits the cranium through the foramen ovale.
  - Divisions within the Mandibular Nerve:
    - Inferior Dental Nerve (Inferior Alveolar Nerve):
      - Description: This is the main trunk that runs through the alveolar bone.
      - Supply: All lower teeth ( $1$ through $8$ ).
      - Associated Gingivae: Labial/buccal gingivae of premolars, canines, and incisors (but not the posterior buccal gingivae of molars).
      - Soft Tissues: Lower lip and chin.
      - Entry Point: Enters the mandible through the mandibular foramen.
      - Anesthesia: An inferior alveolar nerve block provides anesthesia to the body of the mandible, lower portion of the ramus, all mandibular teeth, floor of the mouth, anterior $2/3$ of the tongue, and lingual and labial gingivae of the mandible, as well as the mucosa and skin of the lower lip and chin.
    - Lingual Nerve:
      - Description: Runs lingually.
      - Supply: Lingual gingivae of all lower teeth ( $1$ through $8$ ).
      - Other Structures: Floor of the mouth and touch sensation of the anterior $2/3$ of the tongue.
    - Long Buccal Nerve (Buccal Nerve):
      - Supply: Buccal gingivae of the lower molars ( $6, 7, 8$ ).
    - Mental Nerve:
      - Description: Branches off from the inferior dental nerve.
      - Entry Point: Enters the oral cavity through the mental foramen.
      - Supply: Buccal gingivae of incisors, canines, and premolars; lower lip and chin.

Facial Nerve ( $7^{th}$ Cranial Nerve)

Type: Sensory and motor components.
Primary Supply:
- Some salivary glands.
- Muscles of facial expression.
- Parts of the tongue (taste sensation for anterior $2/3$ ).
Clinical Condition: Bell's Palsy:
- Description: The commonest type of facial palsy, causing acute facial nerve paralysis.
- Cause: Idiopathic (unknown cause), often due to inflammation of the facial nerve, which prevents it from sending correct signals to the brain and facial muscles.
- Symptoms: Affects one side of the face due to a lower motor neuron (LMN) lesion, resulting in:
  - Smoothing of the forehead (inability to wrinkle brow).
  - Drooping eyelid; inability to close the eye.
  - Inability to puff the cheek; asymmetrical smile.
  - Drooping corner of the mouth; dry mouth.
  - Unilateral facial weakness, loss of taste, decreased salivation, and tear secretion.

Glossopharyngeal Nerve ( $9^{th}$ Cranial Nerve)

Primary Supply:
- Throat (pharynx).
- Parts of the tongue (taste and general sensation for posterior $1/3$ ).
- Other salivary glands (parotid gland).

Hypoglossal Nerve ( $12^{th}$ Cranial Nerve)

Type: Motor nerve.
Primary Supply:
- The tongue.
- Innervates the tongue's extrinsic and intrinsic muscles, responsible for tongue movement.
Etymology: Derived from ancient Greek, "hypo" meaning under, and "glossal" meaning tongue.

Blood Supply to the Teeth and Gingivae

Arterial Supply: The teeth and gingivae are supplied by branches of the external carotid artery.
Venous Drainage: Veins draining the oral cavity eventually join the superior vena cava.
Circulation: Deoxygenated blood enters the right side of the heart from the superior vena cava and is then pumped to the lungs for reoxygenation.

Comprehensive Notes on Maxillary and Mandibular Nerve Supply and Anatomy

The Nerve Supply of the Maxilla and Mandible

Chairside Support During Oral Health Assessment (Unit Code H4PW 04)

Bone Structures of the Maxilla and Mandible

The Foramen (Foramina) of the Maxilla and Mandible

Temporomandibular Joint (TMJ)

Nerve Supply to the Oral Cavity (General Principles)

Specific Cranial Nerves Relevant to Dentistry

Trigeminal Nerve (5th5^{th}5th Cranial Nerve)

Facial Nerve (7th7^{th}7th Cranial Nerve)

Glossopharyngeal Nerve (9th9^{th}9th Cranial Nerve)

Hypoglossal Nerve (12th12^{th}12th Cranial Nerve)

Blood Supply to the Teeth and Gingivae

Trigeminal Nerve ( $5^{th}$ Cranial Nerve)

Facial Nerve ( $7^{th}$ Cranial Nerve)

Glossopharyngeal Nerve ( $9^{th}$ Cranial Nerve)

Hypoglossal Nerve ( $12^{th}$ Cranial Nerve)