Dental Anatomy Notes

Cellular Junctions and Oral Cavity Anatomy

• Cellular Junctions:
  • Desmosome: Junction between cells.
  • Hemidesmosome: Attachment of cells to noncellular surfaces.
• Oral Cavity Anatomy & Gingival Tissue:
  • Interdental Gingiva:
    • Interdental papilla fills the embrasure space between teeth.
    • Prevents food impaction.
    • Forms the Col: Concave tissue apical to the contact area between facial and lingual surfaces.
  • Marginal Gingiva:
    • Free gingiva at the gingival margin, continuous with attached gingiva.
    • Similar color to attached gingiva in health.
    • Smooth and loosely attached (not attached to bone), thus no stippling.
    • Masticatory mucosa.
  • Free Gingiva Groove:
    • Separates attached gingiva and marginal gingiva, corresponding to the depth of the sulcus.
  • Gingival Crest:
    • Most coronal part of marginal gingiva.
  • Attached Gingiva:
    • Thick layer of parakeratinized epithelium.
    • Extensive vascular supply.
    • Attached to bone (not mobile), firm, tight, and highly interdigitated, resulting in stippling.
  • Dentogingival Junctional Tissues:
    • Junction between the tooth surface and gingival tissue.
    • Formed from sulcular epithelium and junctional epithelium.
    • Difficult to see clinically.
    • Develops after enamel maturation but before tooth eruption.
    • Formation of Reduced Enamel Epithelium (REE):
      • After enamel formation, ameloblasts and enamel organ form the REE.
      • REE covers the crown of the unerupted tooth.
    • Tooth Eruption:
      • As the tooth erupts, the REE fuses with the oral epithelium.
      • Fusion creates a pathway for tooth emergence.
    • Formation of Junctional Epithelium (JE):
      • Basal cells of the REE proliferate and become the junctional epithelium after eruption.
      • The JE attaches to the enamel (and later cementum) using hemidesmosomes and a basal lamina.
  • Sulcular Epithelium:
    • Crevicular epithelium.
    • Helps create gingival sulcus, with a flow of 1-2 microliters of crevicular/gingival fluid per tooth/hour.
    • Deeper extension is junctional epithelium.
    • Lining mucosa (nonkeratinized); not interdigitated.
  • Junctional Epithelium:
    • Smooth interface (no rete pegs or papillae), making it more permeable than other gingival tissues.
    • Attached to the tooth by epithelial attachment (enamel, dentin, or cementum).
    • Lines the floor of the gingival sulcus in a healthy state.
    • Apical migration of the epithelial attachment indicates periodontitis.
    • JE is thinner than sulcular epithelium.
    • Structures:
      • Internal Basal Lamina: Superficial; tooth-gingiva attachment via hemidesmosomes consisting of lamina lucida and densa.
      • External Basal Lamina: Continuous with internal basal lamina and attaches to connective tissue (CT).
      • Basal Layer: Deepest layer of JE with the fastest turnover time in the entire oral cavity (4-6 days).

Rete Pegs

• Rete pegs are finger-like projections of epithelium that:
  • Anchor it to the underlying tissue.
  • Improve nutrient exchange.
  • Strengthen mechanical resistance.
  • Key to healthy oral structure, especially in the gingiva and tongue.

Mucosa and Epithelium Types

• Lining Mucosa:
  • Soft and moist surface.
  • Ability to stretch and be compressed (mobile).
  • Locations: Buccal, labial, alveolar mucosa, floor of the mouth, ventral (bottom) surface of the tongue, and soft palate.
  • Nonkeratinized.
  • Less pronounced rete pegs.
  • Elastic fibers in connective tissue make it more movable.
  • Submucosa deep to lamina propria allows movement and compression.
  • Local anesthesia is more comfortable due to easier diffusion; sutures needed due to tissue movement.
  • Infections spread rapidly.
  • Fordyce’s granules or spots: Small, yellowish elevations on the surface of mucosa in labial and buccal mucosa, misplaced sebaceous glands in submucosa.
• Masticatory Mucosa:
  • Rubbery surface texture and resiliency.
  • Locations: Attached gingiva, hard palate, and dorsal surface of the tongue.
  • Keratinized.
  • Highly interdigitated.
  • Submucosa might be missing or very thin.
  • Overlying bone increases tissue firmness.
  • Functions in mastication and speech.
  • Local anesthesia is painful due to highly interdigitation.
• Specialized Mucosa:
  • Found on the dorsal and lateral surface of the tongue in the form of lingual papillae.

Mitosis

• Mitosis occurs in the basal layer.

Endocrine vs. Exocrine Glands

• Gland: A structure that produces a chemical secretion necessary for body functioning.
• Types of glands:
  1. Exocrine gland:
     • Associated with a duct that allows glandular secretion to be emptied at its target location.
  2. Endocrine gland:
     • Ductless gland with secretions dumped directly into the blood system and then to its target location.
• Salivary Glands:
  • Major and minor based on size.
  • Both are exocrine glands.
  • Major Salivary Glands:
    • Parotid (Stenson’s duct).
    • Submandibular (Wharton’s duct).
    • Sublingual (Bartholin’s duct).
  • Minor Salivary Glands:
    • Glands of Von Ebner.

Functions of Saliva

• Contains minerals, electrolytes, buffers, enzymes, immunoglobulins, and metabolic wastes.
• Secretion is controlled by the autonomic nervous system (ANS).
• Functions:
  • Lubricates and cleanses oral mucosa.
  • Protects mucosa from dryness and carcinogens.
  • Aids in digestion of food by enzymatic activity.
  • Buffers against acids from food and biofilms.
  • Involved in antibacterial activity (lysozymes).
  • Remineralization of enamel.
  • First step for pellicle formation.
  • Supplies minerals for supragingival calculus formation.

Anatomy of Salivary Glands

• Histology:
  • Composed of epithelium and connective tissue (CT).
  • Epithelial cells line duct system and produce saliva.
  • CT surrounds the epithelium, protecting and supporting the glands.
  • CT Components:
    • Capsule: Surrounds the outer portion of the entire gland.
    • Septum: Divides the inner portion into larger lobes and smaller lobules, carrying nerves and blood vessels.
• Secretory Cells:
  • Epithelial cells that produce saliva.
  • Mucous cells: Produce mucous products for lubrication and barrier formation.
  • Serous cells: Produce serous products of protein and glycoproteins that contain amylase (breaks down starch into sugars).
  • Mixed cells: Produce both mucous and serous products.
• Acini:
  • Group of secretory cells resembling a cluster of grapes.
  • Located at the terminal portion of the gland connected to the ductal system.
  • Consist of a single layer of cuboidal epithelial cells surrounding a lumen.
  • Three Forms:
    • Mucous (thick).
    • Serous (watery).
    • Mucoserous (mixed) or serous demilune.
• Myoepithelial Cells:
  • Located on the surface of some acini and portions of the ductal system.
  • Facilitate the flow of saliva out of each lumen into the connecting ducts.
  • Contractile in nature, squeezing the acinus and forcing saliva out.
  • More than one can be found on a single acinus.
  • Shorten and widen the lumen to keep the ducts open.
• Ductal System:
  • Hollow tubes connected to the acinus, growing larger as they move away from the acinus.
  • Involved in saliva production/modification.
  • Intercalated Duct:
    • Associated with the terminal portion of the gland, attached to the acinus.
    • Adds macromolecular components to saliva such as lysozyme & lactoferrin.
  • Striated Duct:
    • Connected to the intercalated duct.
    • Numerous elongated mitochondria separated by highly folded cell membranes allow metabolic exchange.
    • Can resorb and secrete electrolytes into saliva from blood.
  • Excretory or Secretory Duct:
    • Located in the septum of the gland.
    • Largest in diameter.
    • Saliva exits here into the oral cavity.
• Major Salivary Glands:
  • Parotid (Stenson’s duct).
  • Submandibular (Wharton’s duct).
  • Sublingual (Bartholin’s duct).
• Parotid Salivary Gland:
  • Located behind the mandibular ramus, anterior and inferior to the ear.
  • Largest, encapsulated major salivary gland.
  • Provides 25% of saliva volume.
  • Serous cell dominates.
  • Parotid duct (Stenson’s duct) emerges on the inner surface of the buccal mucosa by the 2nd maxillary molar.
  • Duct opening called parotid papilla, can be mistaken for trauma to the cheek.
• Submandibular Salivary Gland:
  • Lies under the mandible in the submandibular fossa, posterior to the sublingual salivary gland.
  • 2nd largest encapsulated major salivary gland.
  • Provides 60-65% of saliva volume.
  • Mixed products with serous demilunes.
  • Wharton’s duct exits at the sublingual caruncle.
• Sublingual Salivary Gland:
  • Located in the sublingual fossa in the sublingual fascial space at the floor of the mouth, anterior to the submandibular gland.
  • Smallest, and the only unencapsulated major salivary gland.
  • Provides 10% of total saliva volume.
  • Mucous dominates.
  • Bartholin’s duct exits at the sublingual caruncle.
• Minor Salivary Glands:
  • Much smaller but more numerous.
  • Ducts are smaller, located in buccal, labial, and lingual mucosa; soft palate and lateral portions of the hard palate; floor of the mouth.
  • Mostly mucous.
  • Von Ebner’s salivary glands are associated with circumvallate lingual papilla with a serous product to wash away tastes.
• Salivary Gland Development:
  • 6th to 8th week of prenatal development.
  • 3 major glands begin as buds from the lining of the primitive mouth.

Blocked Glands

• Mucocele and Ranula:
  • Obstruction of the salivary duct causes saliva to back up.
  • Caused by a stone (sialolith) or trauma to duct opening.
  • Treatment: Removal of glands or stones by an oral surgeon.
  • Mucocele: Minor salivary gland.
  • Ranula: Submandibular major salivary gland.

Xerostomia

• 30-60% loss of salivary gland tissue occurs with aging.
• Hyposalivation means decreased production of saliva.
• Causes: Medications, tissue destruction from radiation, diseases (diabetes, Sjogren's syndrome, rheumatoid arthritis).
• Results: Increased trauma to nonprotected mucosa, increased cervical caries, problem in speech and mastication, and halitosis (bad breath).
• Treatment:
  • Sipping water.
  • Artificial saliva (Biotene and Oasis).
  • Fluoride rinses.
  • Avoiding alcohol-containing products.
  • Increased recall visits.
  • Saliva-inducing medications if the cause is not medication.

Lingual Papillae

• Found on the lateral and dorsal surface of the tongue.
• Filiform: Increased amount of keratin at the surface, appears whiter; guides food back to the throat for swallowing.
• Fungiform: Mushroom-shaped.
• Foliate: 4-11 vertical ridges parallel to one another on the lateral surface of the posterior portion of the tongue; leaf-shaped.
• Circumvallate: 7-15 large raised mushroom-shaped anterior to the sulcus terminalis, in a V-shaped row; contain taste buds.

Hyperkeratinization

• Hyperkeratinization: Excessive buildup of keratin (a protective protein) in the epithelial surface, especially in keratinized or trauma-exposed tissues.
• Examples: Linea alba, Nicotinic stomatitis on the hard palate.

Repair Process in the Oral Cavity

• Injury → Moist clot from blood forms → Inflammation response triggered → Epithelial cells migrate to form a new epithelial surface under the clot → Clot acts as a guide to form the new surface → Clot breaks down after repair.
• Granulation tissue:
  • Temporary tissue made of fibroblasts, new blood vessels, and immune cells that helps heal wounds.
  • Fills the space and prepares it for final tissue regeneration.
  • Replaced by scar tissue as wound healing completes.

Aging of Oral Mucosa

• Reduction in stippling on attached gingiva.
• Increase in Fordyce’s granules.
• Enlargement of veins on the tongue.
• Reduction in lingual papillae leads to a change in taste perception.
• Changes in salivary glands → Xerostomia.
• Thickness and number of rete pegs in the epithelium diminish.
• Degree of keratinization decreases.
• Turnover time slows down for all tissues.
• Collagen fibers thicken and become dense, stiff, and less elastic.
• Fibroblasts decrease and become less active.
• Ability to repair is reduced, and the time to repair is increased.

Basement Membrane

• Separates connective tissue from epithelium.
• A thin, specialized layer of extracellular matrix that lies between the epithelium and lamina propria.
• Two main layers:
  • Basal Lamina (produced by epithelial cells):
    • Lamina Lucida (closer to the epithelium).
    • Lamina Densa (dense, collagen-rich layer).
  • Reticular Lamina (produced by connective tissue cells):
    • Contains reticular fibers (type III collagen) and anchors the BM to connective tissue.

Bone Types

• Alveolar Bone
  1. Alveolar Bone Proper:
     • Bundle bone (Sharpey’s fibers inserted).
     • Lamina dura (radiopaque on radiograph).
     • Cribriform plate.
     • Plates of compact bone, lining of the tooth socket (alveolus).
     • Alveolar crest is the coronal border of the cervical rim of alveolar bone; 1-2mm apical to the CEJ in health.
  2. Supporting Alveolar Bone (Cortical Plate):
     • Consists of both cortical and trabecular bone.
     • Cortical bone: Plate of compact bone on the facial and lingual surfaces.
     • Trabecular bone between the ABP and plates of cortical bone.
     • Cortical bone is not visible on radiographs (XPA, XBW, occlusal only).
• Other Bony Landmarks:
  1. Interdental Septum (Interdental Bone):
     • Alveolar bone between neighboring teeth consisting of compact and cancellous bone.
  2. Interradicular Septum (Interradicular Bone):
     • Bone between roots of the same tooth, consisting of alveolar bone proper and trabecular bone.
  3. Cancellous, Trabeculated, Spongy Bone:
     • Forms a lattice forming cone-shaped spicules.
     • Blood vessels, nerves, and connective tissue located among trabeculae (source of nutrients).
  4. Compact or Cortical Bone:
     • Lamellae (tight sheets of bone).
     • Osteons (concentric layers of lamellae into cylinders).
     • Haversian canal (vascular canal within osteon).
     • Volkmann’s canal (nutrient canals).

Tooth Movement

• Principle of Compression and Tension:
  • Compression: Along the advancing root surface (PDL is squeezed as the root pushes into the bone).
    • Mobilization of osteoclasts to remove bone.
  • Tension: Along the trailing root surface (PDL is stretched as the root moves away from the bone).
    • Collagen fibers stretched → cells differentiate to become fibroblasts and osteoblasts → form new collagen fibers and bone.
• Orthodontic Tooth Movement:
  • Appliances put pressure on one side of the tooth and adjacent alveolar bone, causing compression in the PDL.
    • Bone resorption on one surface (tooth moves in that direction).
    • Bone formation on the opposite surface.
  • The tooth is stabilized in the new position.
• Mesial Drift:
  • Natural movement where all the teeth move slightly toward the midline over time.
  • Can cause crowding.
  • Occurs slowly.
• Occlusal Drift:
  • A tooth continues to erupt when there is no opposing tooth.

Periodontal Ligament (PDL) on Radiograph

• Appears as a 0.15 - 0.38mm radiolucent space around the tooth, between the lamina dura and cementum.
• No PDL present with implants.

Periodontal Ligaments and Fiber Groups

• Principal fibers:
  • Alveolodental ligament.
  • Interdental (transseptal) ligament.
  • Gingival fiber group.
• Alveolodental Ligament (5 types):
  • Alveolar crest group → Alveolar crest to cementum just below CEJ; first fibers involved with periodontitis.
  • Horizontal group → Inserts into cementum horizontally (90 degrees).
  • Oblique group → Covers apical ⅔ of root; most numerous of the fiber groups.
  • Apical group → Apical region of cementum.
  • Interradicular group → Found only on multi-rooted teeth, no bony attachment; originates in the cementum of one root and inserts into the cementum of the other root.
• Interdental Ligament:
  • No bony attachment; inserts into the neighboring tooth over the alveolar crest but under the junctional epithelium.
  • Reattaches itself apically as periodontitis proceeds.
• Gingival Fibers:
  • Supports only the marginal gingiva to maintain relationship to the tooth.
    1. Circular ligament → Encircles the tooth.
    2. Dentogingival ligament → Inserts in the cementum of the root apical to the epithelial attachment, extends into the marginal gingiva to maintain gingival integrity.
    3. Alveologingival → Alveolar crest coronally into marginal gingiva that helps attach to bone.
    4. Dentoperiosteal → Cementum across the alveolar crest anchors tooth to bone to protect deeper PDL.

Tooth Movement Conditions

• Mesial drift and occlusal drift.
• Tooth loss → bone loss → loss of vertical dimension and leads to attrition of teeth.

Dentin Composition

• 70% inorganic, 20% organic, and 10% water.
• Tubule Relationship:
  • Peritubular → Creates the wall of the dentinal tubule.
  • Intertubular → Found between the tubules.
• Pulpal Relationship:
  • Mantle → First predentin that forms and matures near the DEJ.
  • Circumpulpal → Layer around the outer pulpal wall; the bulk of dentin in the tooth.
• Times of Formation Relationship:
  • Primary → Dentin formed before the apical foramen.
  • Secondary → Dentin formed after completion of the apical foramen; formed throughout the life of the tooth and forms slowly.
  • Tertiary → Aka reparative (tries to seal off injured area); formed quickly in localized areas in response to injury (caries, cavity prep, attrition, or recession); odontoblasts in affected areas may die and undifferentiated cells of the pulp can differentiate into new odontoblasts.
• Specialized Tertiary Dentin:
  • Sclerotic dentin → In association with chronic injury of caries.

Pulp and PDL Cells

• Pulp:
  • Odontoblasts (2nd most common).
  • Fibroblasts (1st most common).
  • Mesenchymal cells (can turn into either odontoblasts or fibroblasts).
• PDL:
  • Blood cells.
  • Endothelial cells.
  • Fibroblast (most common).
  • Cementoblasts.
  • Odontoclasts.
  • Osteoblast.
  • Osteoclast.
  • Mesenchymal cells.
  • Epithelial rests of Malassez.

Pulp Anatomy

• Pulp Chamber (bulk of pulp).
• Two main divisions:
  • Coronal pulp → Located in the crown associated with pulp horns.
  • Radicular pulp → Root pulp, located in the root area; contains apical foramen at the apex (last portion of the tooth to form) and accessory (lateral) canals which are formed when HERS encounters a blood vessel.
• Odontoblastic Layer:
  • Closest to dentin, lines outer pulpal wall containing odontoblastic cell bodies.
• Cell-Free Zone:
  • Next to the odontoblastic layer; not entirely free from cells, just fewer of them; contains a nerve and capillary plexus.
• Cell-Rich Zone:
  • More cells compared to the cell-free zone but less than the odontoblastic layer; consists of an extensive vascular system.
• Pulpal Core:
  • Innermost zone of the pulp; the center of the pulp chamber; lots of cells with vascular supply similar to the cell-rich zone.

Calcium Hydroxyapatite

• Main mineral found in bones and teeth provides hardness and strength.
• Chemical Formula: $Ca₁₀(PO₄)₆(OH)₂$
• Percentage in:
  • Enamel: 96%.
  • Dentin: 70%.
  • Cementum: 65%.
  • Bone: 60%.

Enamel Maturation Process

• Differentiation: IEE cells become columnar and polarized and are called preameloblasts.
• Apposition: Odontoblasts perform apposition of predentin → induce preameloblasts to become ameloblasts → Tomes process is formed → Enamel matrix is secreted from each ameloblast’s Tomes process.
• Maturation:
  • Ameloblasts stop production and start transporting materials for mineralization.
  • Cells remove water and organic material, leaving mostly inorganic matter (high mineral %).
  • Early enamel is partially mineralized.
  • Ameloblasts compress and fuse with OEE to become REE; fused tissue disintegrates during eruption, and ameloblasts are lost forever.
  • Mineralization continues after the eruption of the tooth, though enamel is not a renewable tissue.
• Conditions:
  • Deepened pits and grooves in occlusal surfaces of posterior teeth and lingual of anterior teeth: Created when ameloblasts back into one another, cutting off the nutrition supply, causing incomplete maturation of the matrix → weak or absent enamel.
  • Weak areas are susceptible to caries because bacteria adhere to irregular areas, and plaque biofilm produces acids that slowly demineralize weak areas.

From Cell to Organ

Odontogenesis

• Initiation: Formation of dental lamina, signaling tooth development.
• Bud Stage: Dental lamina forms tooth buds, initiating tooth germ development.
• Cap Stage: Tooth buds develop into a cap-like shape, forming the enamel organ, dental papilla, and dental sac.
• Bell Stage: Differentiation of enamel and dental tissues (ameloblasts); enamel organ becomes 4 different layers, dental papilla becomes 2 layers (outer cells become odontoblasts, and central cells become pulp later). Dental sac produces cementum, PDL, and alveolar bone.
• Apposition: Enamel, dentin, and cementum are secreted in successive layers as a matrix.
• Maturation: Tooth moves through the jawbone and gums to emerge into the oral cavity; reached once tissues have fully mineralized.

Root Formation

• Begins after crown development is finished and the tooth is erupting.
• The cervical loop is the structure responsible for root formation.
• The cervical loop is the most cervical part of the enamel organ; a bilayer consists of OEE and IEE.
• The cervical loop grows deeper into the ectomesenchyme of the dental sac and forms HERS.
• HERS can shape roots, induce dentin formation in the root area, and determines if the root will be curved, straight, short, long, single, or multiple.

Organelles

• Nucleus: Stores genetic code that controls the functions of what the cell performs; controls other organelles within the cell.
• Mitochondria: ATP production provides energy for Krebs’ cycle; site of metabolic reactions that help balance concentrations of H2O, calcium in the cytoplasm.
• Ribosomes: Site of the initiation of protein synthesis.
• Endoplasmic Reticulum: Modification, storage, segregation, and transport of proteins; smooth ER is without ribosomes, and rough ER is with ribosomes.
• Golgi Complex/Apparatus: Segregation, packaging, and transport of proteins from ER; proteins from RER fuse with the Golgi complex and undergo modification by adding carbohydrates, forming glycoproteins; produces lysosomes.
• Lysosomes: Intracellular and extracellular digestion or destruction by phagocytosis.
• Cytoskeleton: 3-dimensional support system for the cell maintains cell shape and stability.

Embryonic Development

• Timeline:
  | Week | Key Developmental Events |
  |:------| - - - - - - - - - - - - - - - - - - - -
  | 1–2 | Fertilization, blastocyst, implantation |
  | 3 | Germ layers form (ectoderm, mesoderm, endoderm); neural crest cells |
  | 4 | Pharyngeal arches; face begins; dental lamina appears |
  | 5 | Nasal structures, early tongue; jaws grow |
  | 6 | Tooth buds form; palate starts |
  | 7–8 | Upper lip and palate fuse; tooth cap/bell stage |
  | 9–12 | Enamel/dentin form; facial features develop; root formation starts|

Cleft Lip and Palate

• Cleft Lip: Failure of fusion of the maxillary processes with the medial nasal process.
• Cleft Palate: Failure of fusion of the palatal shelves (maxillary processes) with the primary palate and/or each other.

Embryonic Structure Formation

Regions of the Face

• Frontal: Forehead and the area above the eyes.
• Orbital: Eyeball and supporting structures contained in the orbit (eye socket).
• Nasal: External nose, root of nose, apex of nose, and nares (nostril), nasal septum, and alae.
• Infraorbital: Inferior to the orbital region and lateral to the nasal region.
• Zygomatic: Lateral to the infraorbital region, overlies the zygomatic arch; extends just lateral to the margin of the eye and toward the middle part of the external ear.
• TMJ: Inferior to the zygomatic arch and anterior to the external ear.
• Buccal: Lateral to the oral and mental region and inferior to the zygomatic region; the masseter muscle is palpated when the patient clenches together; the angle of the mandible is the sharp angle of the lower jaw, which is inferior to the earlobe.
• Oral: Superior to the mental region and medial to the buccal region; includes the vermillion zone, philtrum, tubercle, labial commissure, and mucocutaneous junction.
• Mental: Inferior to the oral region and medial to the buccal region; includes the mandibular symphysis, ramus, coronoid process and notch, mandibular condyle and notch.