Oral/Dental Anatomy Review

Embryology and Oral/Dental Anatomy Outline

1. Development of the Oral Cavity

  • Frontal Process

    • Forehead and frontal bone

    • Median Nasal Process

    • Center and tip of the nose, nasal septum

    • Globular Process

    • Forms philtrum and premaxilla

    • Lateral Nasal Process

    • Forms sides of the nose and infraorbital region.

2. Pharyngeal Arches

  • 1st Brachial Arch (Pharyngeal Arch): Mandibular Arch (CN V)

    • Maxillary Process

    • Forms palatal shelves, lateral processes, palatal processes, upper cheeks, sides of the lip.

    • Mandibular Process

    • Forms mandible, lower face and lip, anterior 2/3 of tongue.

  • Posterior 1/3 of Tongue

    • Originates from 2nd and 3rd arches.

  • Buccopharyngeal Membrane

    • Ruptures in the 4th week to open mouth.

  • Development Failures:

    • Upper lip failure occurs at week 6-8 due to non-fusion of median nasal and right/left processes.

    • The palate fails to fuse (globular and right/left maxillary processes) from week 6-12.

3. 2nd Brachial Arch (Hyoid Arch)

  • Associated with cranial nerves:

    • 1st Arch: Trigeminal Nerve (CN V)

    • 2nd Arch: Facial Nerve (CN VII)

    • Includes muscles of facial expression and part of the tongue.

    • 3rd Arch: Glossopharyngeal Nerve (CN IX)

    • 4th to 6th Arches: Vagus Nerve (CN X)

4. Odontogenesis

  • Ectoderm: Enamel, skin, lining of the oral mucosa, nervous tissue, enamel organ.

  • Mesoderm: Skeletal, cardiac and smooth muscle, dental papilla, dental sac.

  • Endoderm: Lining of internal organs, including lungs, digestive tract, thyroid.

  • Stomodeum: Primordial mouth from where enamel originates from ectoderm.

  • Dentin, Cementum, Pulp: Derived from ectomesenchyme cells (neural crest cells).

5. Root Formation

  • Hertwig's Epithelial Root Sheath (HERS): Determines the shape of the root.

    • Malassez cells are remnants of HERS.

    • Roots form 1-4 years after eruption.

  • Stages of Tooth Formation:

    1. Initiation: Dental lamina forms.

    2. Bud Stage: 20 different buds form within dental lamina.

    3. Cap Stage: Proliferation of enamel organ.

    4. Bell Stage: Differentiation occurs, leading to the formation of enamel, dentin, pulp, etc.

    5. Apposition Stage: Secretion of matrix, including calcium phosphate.

    6. Maturation Stage: Formation of hydroxyapatite crystals.

6. Tooth Tissues

  • Enamel: 96% mineral; formed by ameloblasts from inner enamel epithelium (IEE).

  • Dentin: 70% mineral; odontoblasts form dentin from dental papilla.

    • Primary Dentin: Mantle dentin; initial layer laid down by odontoblasts.

    • Secondary Dentin: Forms after teeth enter occlusion as reparative dentin.

  • Cementum: 70% mineral; thickest at the apex and derived from dental sac.

  • Pulp: Contains fibroblasts, odontoblasts, histiocytes, blood vessels, nerves; from dental papilla.

  • PDL: Periodontal ligament; contains Sharpey's fibers, sensory nerves, derived from dental sac.

7. Histology Vocabulary

  • Cell Membrane: Lipid bilayer; regulates passage of materials.

  • Nucleus: Storage of DNA/RNA.

  • Cytoplasm: Site for metabolic activities; viscous gel.

  • Lysosomes: Contain digestive enzymes (like lysol).

  • Golgi Apparatus: Involved in the packaging of secretions and proteins.

  • Mitochondria: Produce ATP.

  • Rough Endoplasmic Reticulum: Produces proteins.

8. Oral Mucosa and Bone Structure

  • Masticatory Mucosa: Keratinized; includes gingiva and hard palate.

  • Lining Mucosa: Non-keratinized; includes cheeks, floor of mouth, soft palate.

  • Specialized Mucosa: On the dorsum of the tongue.

  • Alveolar Bone (Dental Sac):

    • Cortical Bone: Compact; forms the walls of sockets.

    • Cribriform Plate: Alveolar bone proper (lamina dura).

    • Cancellous Bone: Spongy bone in trabecular pattern.

9. Bones of the Skull

  • Cranial Bones:

    • Frontal, Occipital, Ethmoid, Sphenoid, Temporal, and Parietal.

  • Facial Bones:

    • Mandible, Maxilla, Vomer, Nasal, Lacrimal, Zygomatic, Palatine, and Inferior Nasal Concha.

  • Sutures:

    • Coronal, Sagittal, Lambdoidal, Squamous.

10. Hyoid Bone

  • Definition: Horseshoe-shaped, inferior to mandible; does not articulate with other bones.

11. TMJ (Temporomandibular Joint)

  • Components:

    1. Temporal Bone: Features include mandibular fossa, glenoid fossa, articular eminence.

    2. Mandible: Includes the condyle.

    3. Articular Disc (Meniscus): Divides joint into upper/lower cavity.

    4. Joint Capsule: Surrounds joints, secretes synovial fluid.

  • Movement Types:

    • Hinge (rotation) and Gliding (translation).

12. Nerve and Muscle Definitions

  • Ligament: Attaches bone to bone.

  • Tendon: Attaches muscle to bone.

  • Trismus: Limited opening of the jaw.

  • Luxation: Dislocation of the condyle.

  • Muscle Movements:

    • Elevation, Depression, Protraction, Retraction, Lateral Deviation.

13. Neural Pathways and Cranial Nerves

  • Nervous System:

    • Afferent: Arrivals to the brain; sensory.

    • Efferent: Exits; motor responses.

  • Cranial Nerves:

    • Trigeminal (V), Facial (VII), Glossopharyngeal (IX), Vagus (X), Accessory (XI), and Hypoglossal (XII).

14. Sensory and Motor Functions of Cranial Nerves

  • Olfactory (I): Sense of smell.

  • Optic (II): Sense of sight.

  • Oculomotor (III): Eye muscle control.

  • Trigeminal (V): Sensation and mastication.

  • Facial (VII): Muscles of facial expression, taste to anterior 2/3 tongue.

15. Dental Innervation and Blood Supply

  • Dental Innervation:

    • Anterior Superior Alveolar (ASA): Upper anterior teeth.

    • Middle Superior Alveolar (MSA): Maxillary premolars.

    • Posterior Superior Alveolar (PSA): Molars (except MB root of 1st molar). Mental Nerve: Supplies lower lip and chin.

  • Blood Supply:

    • Arteries carry oxygenated blood, veins return deoxygenated blood.

16. Salivary Glands

  • Types of Salivary Glands:

    1. Parotid Gland: Innervated by glossopharyngeal (CN IX).

    2. Submandibular Gland: Mostly serous; innervated by facial nerve (CN VII).

    3. Sublingual Gland: Mostly mucous; also innervated by CN VII.

  • Functions of Saliva: Moistens, cleanses, lubricates, buffers oral pH.

17. Tooth Eruption and Dentition

  • Permanent Dentition Eruption Sequence:

    • Mandibular centrals (6-7 years) - Maxillary centrals (7-8 years)

    • Canines (9-12 years) - 1st Molars (6-7 yrs) - 2nd Molars (11-13 yrs).

18. Anatomic Fun Facts**:

  • Most often missed area during scaling: Mesial coronal/root concavity of maxillary first premolar.

  • Tooth with the longest root: Maxillary canine.

  • Premolar most often with two roots: Maxillary first premolar.

  • Non-functional lingual cusp: Mandibular first premolar.

  • Tooth most affected by microdontia: Maxillary lateral incisor.

19. Tooth Characteristics and Functions

  • Distinction between incisors and molars based on occlusal and buccal surfaces.

  • Clinical relevance of developmental lines, grooves, mamelons, and cingulum in tooth identification.