Overview

Question 1

Oral cavity proper

Answer 1

1. Bounded by lingual surface of the teeth and alveolar bone (and associated oral mucosa) anteriorly and laterally. Superiorly it is bounded by the bone and soft tissue of the hard palate.
2. Is bounded by musculature inferiorly (floor of the mouth).
3. Is open posteriorly and communicates with the oropharynx via the fauces which lie between the glossopalatine arches. The isthmus of the fauces is bounded above by the soft palate and below by the base of the tongue.

Question 2

Oral Vestibule

Answer 2

1. Bounded anteriorly by the inner surface of the lips.
2. Bounded laterally by the inner surface of the cheeks.
3. Bounded posteriorly by the labial surface of the teeth and alveolar bone (and associated oral mucosa).
4. Bounded superiorly and inferiorly by the reflection of the oral mucosa of the lips and cheeks as it becomes continuous with the oral mucosa covering the bone (alveolar mucosa and gingiva).
5. The oral cavity is considered to be the oral cavity proper plus the vestibule

Question 3

General tooth anatomy

Answer 3

1. Crown
   
   1. The crown of the tooth can be defined in two ways.
   2. The anatomical crown is that part of the tooth that is covered by enamel.
   3. The clinical crown is that part of the tooth that is exposed to the oral environment.
   4. Thus, in newly erupting teeth the clinical crown can be smaller than the anatomical crown.
   5. In older individuals, following significant gingival recession and exposure of the anatomical root, the clinical crown may be larger than the anatomical crown
2. Root
   
   1. The root of the tooth is not covered with enamel but is covered with cementum.
   2. The junction between anatomical the crown and the root is considered to be the cervix or neck of the tooth. This junction is not absolute.
   3. Cementum may meet the enamel at a sharp line, overlap it slightly, or not meet it at all

Question 4

The hard tissues of the tooth (quick summary)

Answer 4

1. Enamel
   
   1. Covers the crown; consists of enamel rods; deposited by the activity of epithelial cells; in the mature state is almost entirely mineral; growth lines are Stria of Retzius
2. Dentin
   
   1. Forms the bulk of the tooth; hard tissue formed by the activity of odontoblasts of neural crest origin; tubular collagenous matrix; growth lines are called incremental lines of von Ebner and contour lines of Owen
3. Cementum
   
   1. Covers the root surface; hard tissue is formed by the activity of cementoblasts; cells are also derived from the neural crest; acellular cementum is found on the surface of the root nearest the cervix and cellular cementum nearer the apex of the root; cellular cementum contains cementoblasts in lacunae

Question 5

The soft tissue within the tooth (quick summary)

Answer 5

1. Pulp
   
   1. Connective tissue; consists of undifferentiated cells, fibroblasts and other cellular elements common to all connective tissues; blood vessels, nerves, lymphatics; outermost layer of cells are the odontoblasts

Question 6

Supporting Structures of the Tooth (quick summary)

Answer 6

1. Alveolar bone
   
   1. Surrounds the tooth; inner layer is called the alveolar bone proper cribriform plate or lamina dura
2. Periodontal Ligament
   
   1. Provides the fibrous attachment connecting the tooth to the alveolar bone; Sharpey’s fibers of the periodontal ligament are found within the cementum and alveolar bone; periodontal ligament contains cells which contribute to the ligament, the cementum, and the alveolar bone
3. Junctional (attachment) epithelium
   
   1. Epithelial cells of the gingiva form a collar and are attached to the tooth by hemidesmosomes
4. Gingiva
   
   1. Connective tissue and epithelium that surrounds the tooth and indirectly supports the tooth; the transseptal ligament which runs from tooth to tooth can be thought of as either a gingival or periodontal component

Question 7

Oral mucosa

Answer 7

1. Is the soft tissue covering all the structures of the oral cavity except the clinical crowns of the teeth
2. It consists of an epithelial covering of stratified squamous epithelium and can be keratinized or nonkeratinized (depending on location).
3. A lamina propria underlies the epithelial layer
4. Depending on location, the oral mucosa may have a supporting submucosa or a mucoperiosteum
5. The tongue is covered with a specialized oral mucosa that contains taste buds

Question 8

Enamel

Answer 8

1. Basic building block of mature enamel is enamel rod
2. A parallel array of elongated apatitic crystals
3. Organic matrix is primarily located in the Rod Sheath
4. Organic matrix also has been detected in the intercrystalline spaces of rods.
5. Trajectories of the rods (decussation pattern) vary between different teeth and differet locations in an individual tooth
6. Graded structural and compositional properties of enamel
   
   1. High Mg, CO₃ apatite and organic content closer to the DEJ than those further away.

Question 9

Dentin

Answer 9

1. Circumpulpal dentin comprises the bulk of crown dentin; it consiste of Intertubular (ITD) and Peritubular (PTD) dentin.
2. Intertubular dentin is a bone-like tissue comprised of mineralized collagen fibrils.
3. Peritubular dentin is a thin dense layer of dentin, surrounding the tubules.
   
   1. Lacks collagen
   2. Higher mineral content
4. Dentino-enamel Junction (DEJ) provides a robust interface, which performs for decades without major failure
   
   1. Tooth crowns consist of two mineralized tissues with strikingly different compositional and structural properties
   2. Dentin
      
      1. 70% w/w mineral
      2. 20% w/w organics
      3. 10% w/w water
   3. Enamel
      
      1. 95% w/w mineral
      2. <4% w/w water
      3. >1% w/w organics
         4.

Question 10

Dental pulp

Answer 10

1. Originates from neural crest
2. Consists of several morphological layers
3. Outer layer of odontoblasts (unique dentin-forming cells)
4. Highly vascularized and highly innervated

Question 11

Cementum

Answer 11

1. The outer layer of the root
2. Contains mineralized collagen, similar to dentin but softer (except afibrillar cementum)
3. Forms interface between dentin and periodontal ligament
4. Afibrillar cementum forms on the top of cementum or enamel, does not contain collagen fibrils and it is not involved in PDL attachmeent. Its origin is not clear
5. Has a layered rotated plywood structure, with collagen fibrils oriented in plane with the root surface

Question 12

Periodontal ligament (PDL)

Answer 12

1. Ligament tissue connecting roots of the teeth to the alveolar bone
2. Consists of parallel arrays of collagen fibrils, running roughly normal to the surfaces of bone and cemntum
3. Epithelial Periodontium
   
   1. Sulclar epithelium lines the gingival sulcus
   2. Junctional epithelium lies at the floor of the sulcus and is attached to the tooth surface
   3. Junctional epithelium binds to enamel surface

Question 13

Junctions and Interfaces: meeting of dissimilar tissues (potential weak points)

Answer 13

1. Cemento-enamel Junction where cementum and enamel meet at the cervix of the tooth
2. Dentino-enamel junction where dentin and enamel meet, most visible in sections
3. Cemento-dentinal Junction where dentin and cementum meet
4. Mineralization front of dentin where dentin and predentin meet
5. Periodontal Ligament connects teeth to the alveolar bone
6. Epythelium-Enamel Junction (junctional epithelium)

Question 14

Alveolar bone

Answer 14

1. Alveolar bone forms a socket around the tooth
2. Alveolar bone provides an attachment surface for the tooth
3. Alveolar bone has outer compact (cortical plates) and inner trabecular (spongiosa) areas

Question 15

Composition of bone

Answer 15

1. Organic (30-40% w/w):
   
   1. Collagen (90% of ECM)
   2. Proteoglycans: biglycan and decorin
   3. Noncollagenous proteins
      
      1. Osteonectin
      2. SIBLING family of proteins (DMP1, BSP, DSPP, Osteopontin, MEPE)
      3. Thrombospondin
      4. Fibronectin
      5. Osteocalcin (bone Gla)
   4. Growth Factors (BMPs, FGF, IGF, PDGF)
2. Inorganic:
   
   1. Mineral (carbonated apatite) 50-60% w/w
   2. Water 10%

• Mineralized collagen fibrils are basic building blocks of bone and dentin.
  *

Question 16

Types of oral mucosa

Answer 16

1. Non-keratinized (cheek)
2. Keratinized (hard palate, gingiva)
3. Attached & mobile oral mucosa
4. Oral mucosa clasification:
   
   1. Masticatory mucosa- resists the shearing and compressive forces of mastication. It’s epithelium is orthokeratinized; e.g., gingiva and hard palate.
   2. Lining mucosa– is glandular and its epithelium is non-keratinized or parakeratinized. It contains glands; e.g., lingual surface of the lip, buccal surface of the cheeks, soft palate, floor of the mouth and ventral surface of the tongue.
   3. Specialized mucosa– dorsal surface of the
      tongue is highly innervated, contains test buds

Question 17

Temporo-Mandibular Joint (TMJ)

Answer 17

1. Unique joint, two points of attachment
2. Degradation of TMJ causes a severe condition, severe pain, limited movement of the jaw