Endo

Question 1

Dental Lamina

Answer 1

• First stage of tooth developement
• originates from oral epithelium
• pulp

Question 2

Oral epithelium

Answer 2

• Where tooth developement begins

Question 3

Stages of tooth development

Answer 3

1. Bud stage
2. Cap stage
3. Bell stage

Question 4

Bell stage

Answer 4

• Ectomesenchyme begins to condense arguing tooth germ

Question 5

Dental Papilla

Answer 5

• Derived from ectomesenchymal cells
• develops into dental pulp
• Basophilic (Blue) staining

Question 6

Bell stage

Answer 6

• Formation of an incisor
• Inner layer differentiates into ameloblasts
• Outer layer differentiates into Odontoblasts

Question 7

Odontoblasts

Answer 7

• Origin: Ectomesenchymal cells
• Undifferentiated ectomesenchymal cells
  
  • Lie underneath ectomesenchymal cells
  • serve as a reservoir
  • can differentiate into anything
  • secrete growth and signaling factors to control differentiation to odontoblasts
• Secrete Dentin
• Terminal cells
  
  • can’t change into nay other type of cellS

Question 8

Amelobasts

Answer 8

• Origin:
  
  • inner dental epithelium
• immediately adjacent to odontoblasts
• Initiation:
  
  • once dentin formation starts
    
    • odontoblasts secrete dentin and cytokines to activate
• Epithelial/Mesenchymal interaction

Question 9

Dentin Formation

Answer 9

• Begins at cusp tip
• Progresses apical at 4.5um/day
• Mantle dentin
  
  • first dentin produced by odontoblasts
• Predentin
  
  • 50 microns thick
  • Is the dentin matrix adjacent to the odontolayer
  • not mineralized but will over time

Question 10

Root formation

Answer 10

• Initiation by HERS
  
  • apical proliferation of the 2 fused epithelia of cervical loupe (inner and outer dental epithelia)
  • Sends signal to odontoblasts to secrete dentin
  • Template for what kind of root
  • Horizontal segments join to form epithelial diaphragm
• Hyaline layer of Hopewell-Smith
  
  • helps bind cementum to dentin
• As the tooth continues to develop, the HERS will fragments
  
  • allows dental follicle cells to differentiate into cementoblasts
  • some become epithelial rests of malassez
    
    • cysts

Question 11

Cervical Loupe

Answer 11

• Where the cells of inner and outer dental epithelia meet during root formation

Question 12

Lateral Canals

Answer 12

• Communicate between pulp and PDL
• Forms when the root sheath is fragmented before dentin formation
• can Be located anywhere
• most common in apical 1/3
• can allow pulpal disease to spread to the periradicular tissues
• occasionally allows perio disease to spread to the pulp

Question 13

Apical Foramen

Answer 13

• Opening that allows pulpal blood vessels and nerves to enter and exit the tooth
• Single or multiple
• Sometimes located at the end of the anatomic root
• Diameter varies: 0.3-0.6

Question 14

Pulp Function

Answer 14

• Induction
• Formation
• Nutrition
• Defense
• Sensation

Question 15

Induction

Answer 15

• Interdependent functions
• enamel epithelium induces differentiation of odontoblasts
• Odontoblasts and dentin induce formation of enamel

Question 16

Pulp Function: Formation

Answer 16

• Odontoblasts
  
  • secrete inorganic matrix
  • transport inorganic components to the matrix
  • create enviroment that helps matrix mineralization
• Primary Dentinogenesis (tooth formation)
  
  • well organized pattern of tubules and cell processes
• Secondary Dentinogensis
  
  • slower
  • less symmetric
• Tertiary Dentinogenesis
  
  • less organized
  • localized to site of injury
  • 2 types:
    
    • Reactionary:
      
      • formed by original odontoblasts
      • tubular
    • Reparative
      
      • formed by new odontoblasts
      • Atubular

Question 17

Pulp Function: Nutrition

Answer 17

• Provides hurries to blood supply

Question 18

Pulp function: Defense

Answer 18

• Forms dentin in response to injury
• identifies foreign substance
• elicit immune response

Question 19

Pulp Function: Sensation

Answer 19

• Pain fibers only
  
  • Myelinated fibers
    
    • fast
    • sharp pain
  • Non-myelinated
    
    • slow
    • dull pain

Question 20

Cells of pulp

Answer 20

• Odontoblasts
• Stem cells
• Fibroblasts
• Cells of the immune system

Question 21

Cells of the Pulp: Odontoblasts

Answer 21

• Characteristic cell of the pulp
• Synthesizes matrix
• Controls mineralization
• Coronal shape: columnar
• Apical shape: flattened
• 45k-65k coronally
• end cell
• functional, transitional, resting phases
• 2 major components:
  
  • Cell body
  • Cell process
• Cell body joined by membrane juncitons:
  
  • Desmosome: Mechanical link
  • Gap junction: communication
  • Tight Junction: control permeability
• Cell membrane receptors:
  
  • Toll-like receptor
  • Capsacin Receptor
  • Vanilloid Receptor

Question 22

Cells of the Pulp: Stem Cells

Answer 22

• AKA preodontoblasts
• present throughout the pulp
• Most dense at the core

Question 23

Cells of the Pulp: Fibroblasts

Answer 23

• most common cell type in pulp
• Greatest number in coronal pulp
• Produce:
  
  • collagen
  • ground substance

Question 24

Cells of the Pulp: Cells of the immune system

Answer 24

• Dendritic cells
  
  • most prominent cell
  • Antigen presenting cells
  • found mosty in odontoblastic layer and around blood vessels
• Macrophages
  
  • Histiocytes (Resting form)
• T-Lymphocytes

Question 25

Extracellular Components: Fibers

Answer 25

• Type I collagen
  
  • most prominent
• Type I: Type III
  
  • 55:45
• Odontoblasts: type I
• Fibroblasts: Type I and III
• Fibrillin
  
  • only non-collagenous fiber
  • large glycoprotein