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Oral Sciences > Unit 3a - Development of Tooth Tissues > Flashcards

Unit 3a - Development of Tooth Tissues Flashcards

1
Q

What is odontogenesis?

A
  • The development of the dental tissues that begin in the embryo at approximately 6-7 weeks
  • continues until the individual is in his/her late teens
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2
Q

Which layer are teeth produced from?

A
  • Teeth are produced from epithelial tissue from the ectoderm layer (in the case of the enamel)
  • Mesenchyme (undifferentiated embryonic connective tissue that is a mixture of mesoderm and neural crest cells)make the remaining tooth tissues of mesodermal origin (sometimes called ectomesenchyme)
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3
Q

Describe the initiation stage of odontogenesis.

A
  • begins with a thickening of ectoderm along the surface of the jaw - known as dental lamina
  • 10 points on each arch which is the beginning of an individual tooth germ
  • some cells continue to proliferate deeper into the mesenchyme
  • this particular tissue structure will eventually form tooth enamel and when enamel is being produced, it is sometimes referred to as the enamel organ, or dental organ
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4
Q

Describe the bud stage

A
  • the group of cells proliferating from teh dental lamina stretches out as it proliferates and takes on a rounded appearance
  • each bud structure is associated with a sphere of condensed mesenchyme at the base which will eventually become the dental papilla
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5
Q

What does the dental papilla form?

A

the future dentin and pulp

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6
Q

Describe the cap stage

A
  • the deepest part of the developing bud structure becomes concaved
  • 3 distinct layers: enamel organ, dental papilla and dental follicle
  • dental follicle (also known as the dental sac) is an area of condensed mesenchymal cells and fibers that surround the dental papilla and the enamel organ
  • the enamel organ is still attached to the epithelium of the stomodeum by the dental lamina (remains in tact until the early Bell stage)
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7
Q

What will form from the dental sac?

A

the PDL, alveolar bone and the cementum

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8
Q

What is the OEE?

A

outer enamel epithelium - on outer most part of the cap structure

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9
Q

What is the IEE?

A

inner enamel epithelial - continuous with the OEE and outlines the concavity forming the cap shape. this layer of cells is responsible for forming the future shape of the tooth crown (think of this as a 3 dimensional shape/we can only see 2 dimensions on a diagram)

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10
Q

What is the SR?

A

Stellate reticulum - cells that are between the IEE and OEE

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11
Q

What is the cervical loop?

A

-the area where the IEE and the OEE meet

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12
Q

Where is the basement membrane located during the cap stage?

A

between the enamel organ and the connective tissue of the dental papilla
- it is similar to any other that is situated between epithelium and connective tissue

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13
Q

Describe the bell stage

A
  • a fourth layer of cells forms within the enamel organ during this stage
  • stratum intermedium
  • further morphodifferentiation
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14
Q

What is the SI?

A
  • the fourst layer of cells that forms within the enamel organ during the bell stage
  • lays between the IEE and the stellate reticulum (SR)
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15
Q

Describe the late bell stage

A
  • changes are occurring to the IEE cells in preparation for enamel production
  • the cells of the IEE elongate into enamel producing cells and are called preameloblasts
  • odontogenesis - dentin and enamel formation *cusps and incisal edges first
  • peripheral cells of he dental papilla are lining up along the basement membrane; also changing shape and becoming odontoblasts
  • BM shows the outline of a tooth shape and marks the line of the future DEJ
  • once odontoblasts begin their production of predentin, the preameloblasts form a secreting end, the Tomes Process, and are then productive ameloblasts
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16
Q

Which cells produce dentin?

A

Odontoblasts

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17
Q

When does the first hard (mineralized) tooth structure form in an embryo?

A
  • approximately 5 months
  • dentin preceding enamel slightly
  • the cusp tips also precede the more coronal portions of the crown
  • once the hard tissues begin to form, a signal is transmitted for the dental lamina to break up and disintegrate, leaving the tooth germ independent of the oral eptihelium
  • some cells of the dental lamina remain as eptihelial cell rests and have the potential for cyst development or to undergo keratinization and then form the Glands of Serres
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18
Q

What are Glands of Serres

A
  • cells of the dental lamina left behind from disintegration of the dental lamina
  • they enlarge, undergo keratinization and appear as white bumps under the mucosa of a newborn baby
  • these are lost as the tooth erupts (no dental intervention is required)
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19
Q

What is secondary dental lamina?

A
  • gives rise to a successional tooth germ
  • differentiation of the cells of the dental papilla into odontoblasts and of the IEE into ameloblasts, a successional lamina or secondary dental lamina is proliferating from the primary
  • successional teeth develop in a position that is lingual to the primary tooth germ
  • primary dental lamina = primary, 6,7,8
  • secondary dental lamina=1-5 successional teeth!
20
Q

What are some clinical concerns regarding the formation of hard tissues?

A
  • recognition of developing teeth/stages
  • counseling for adequate nutrition for optimum development and growth
  • effects of drugs and radiation on developing teeth
  • alveolar bone and developing teeth/higher risk for trauma
  • trauma to jaw could be devastating as the bone is not fully developed - could stop, change or start growth of the bone
21
Q

What is proliferation?

A

Growth and increase in number of cells

22
Q

What is histodifferentiation?

A

cells differentiate and become specialized

23
Q

What is morphodifferentiation

A

growth in terms of shape and form

24
Q

What is apposition?

A

deposition of the matrix for hard dental structures

25
Q

What are some developmental anomalies in tooth formation?

A
  1. hypodontia or anodontiat
  2. supernumerary teeth, cusps
  3. peg laterals (also microdontia)
  4. altered shape to tooth crowns (mulberry molars)
  5. gemination (twinning)
  6. development of teeth in abnormal locations
  7. fusion
  8. Glands of Serres
26
Q

Describe the beginning stages of dentinogenesis

A
  • the cells of the dental papilla stimulate the IEE cells to differentiate
  • the IEE cells then elongate into preameloblasts
  • they in turn stimulate the cells of the dental papilla to differentiate into odontoblasts (line next to DEJ)
  • the production of dentin begins before the ameloblasts form enamel
  • dentinogenesis begins in late bell stage
27
Q

Describe dentinogenesis

A
  • newly differentiated odontoblasts begin to move away from teh basement membrane in a wave-like fashion toward the centre of the dental papilla (pulp), leaving behind a cytoplasmic extension and predentin matrix (covers everything but the apical foramen)
  • as the odontoblasts produce predentin matrix, the fibers in the outer aspect of future dentin (near the DEJ) are much coarser than those towards the center and inner dentin
28
Q

Describe the composition and structure of dentin

A
  • 30% organic nonmineralized - composed of collagen fibers, ground substance and H2O
  • 70% nonorganic mineralized -
  • cells are odontoblasts originating from the pulp area. Movement of the cells during development of dentin is towards pulp laying down matrix along the way. NOTE: this is the opposite direction from enamel formation.
  • dentin makes up the majority of tooth structure; located below crown enamel and root dentin
  • included in the crown and root
  • highly elastic *vital throughout life of the tooth
29
Q

Describe the primary curvature of tubules

A
  • it is the curvature of tubules in an S pattern from the DEJ
  • general direction: perpendicular to DEJ/DCJ *straighter in root dentin
  • reflects path of odontoblasts *pulp is getting smaller
  • extend from deintoenamel junction to the dentinocementum junction
30
Q

Why would you see branching in dentinal tubules?

A
  • occurs throughout dentin matrix - more at DEJ/DCJ
  • possible anastomoses between adjacent tubules
  • theres an increase in organic tissue due to lateral branching
  • can attach to adjacent tubules
  • scalloped at DEJ therefore increasing the connection of 2 tissues together
  • increases the number of tubules per unit of area
31
Q

Describe odontoblasts and odontoblastic process of dentinogenesis

A
  • odontoblasts are always located on the pulp side of the dentin
  • they will continue to produce dentin as long as the tooth is vital
  • cell process will continue to extend into the tubule; over time somewhat receding
  • will vary with tooth and individual and over time the tubules may become filled with other tissue products
  • sensory nerve axons are present in some tubules - terminates at the odontoblastic process
32
Q

What is predentin?

A
  • as the odontoblasts move inward, finer fibers are depsotied along with ground substance of the dentin matrix
  • the intial matrix laid down is referred to as predentin because it is not mineralized
  • odontoblastic (cytoplamsic) process becomes surrounded by dentin and is enclosed in a dentinal tubule
  • after matrix is formed it begins to calcify
  • odontoblasts are vital and provide nutrients to dentin throughout life
33
Q

What make up the dentinal matrix?

A

peritubular dentin
- highly mineralized

intertubular dentin

  • less mineralized
  • forms majority of dentin
  • little change over time
  • include side branches of dentinal tubules
34
Q

What are the different areas of dentin?

A

Mantle Dentin
Circumpulpal Dentin
Globular/Interglobular Dentin

35
Q

What is mantle dentin? Where is it located?

A
  • first dentin formed
  • mainly in crown next to DEJ
  • more peritubular/larger collagen fibers that are perpendicular to the DEJ in intertubular
36
Q

What is circumpulpal dentin and where is it located?

A
  • nearest to the pulp

- composes majority of root dentin

37
Q

What is globular/interglobular dentin and where is it located?

A
  • right under mantle denint
  • names are interchangeable and only pertain to their location
  • related to the pattern of calcification
  • contains less or no peritubular dentin = pattern
  • defect is in mineralization not in formation
  • dentinal tubules pass through uninterrupted
  • glubular and linear patter of dentin calcification process - note incomplete fusion of globules
38
Q

What is the Tome’s Granular Layer?

A
  • adjacent to DCJ * root only
  • small masses of hypomineralized dentin
  • first dentin formed in root *possibly due to initial orientation of odontoblasts at DCJ
  • histological granular appearance = name
39
Q

What are contour lines of Owen?

A
  • exaggerated lines of von Ebner
  • hypocalcified bands associated with : changes in metabolism during development (not as regular as vonEbner’s
  • need higher magnification to see vonEbner
40
Q

What are neonatal lines?

A

-contour lines in dentin

41
Q

What is primary dentin?

A
  • all dentin formed prior to the tooth reaching fucntional occlusion
  • includes mantle
  • pattern = regular and consistent
42
Q

What is secondary dentin?

A
  • formed after fucntional occlusion/apical dentin formed (suggests that odontoblasts receive a signal to slow down)
  • slower forming than primary - pattern not as even
  • may be less calcified - continues throughout the life of the tooth
43
Q

What is reparative/reactive dentin?

A
  • another type of secondary
  • forms quickly * in response to an irritant
  • forms under cusps or decay * not over entire pulp wall
  • various patterns (next slide)
  • if injury is sever, may destroy odontoblasts
44
Q

What is sclerotic dentin?

A
  • peritubular dentin - calcium slats fill tubules
  • defense mechanism
  • adjacent to irritant
45
Q

What are dead tracts?

A
  • odontoblasts withdraw
  • tubules are vacant
  • air fills tubules in histology process
  • channels to pulp
46
Q

What happens to odontoblastic processes with age?

A
  • young - process extends mostly to DEJ/DCJ
  • over time it recedes 1/2 way or more
  • tubule may fill with tissue fluid, calcium salts, or collagen fibers/fluid
  • significance is that once the tubule is open, it becomes a channel for microorganisms, dental materials (stain) pulp damage - *response of odontoblasts to irritants is less than in young pulp
47
Q

What are some clinical considerations for dentin?

A
  • dentin does not remodel - but odontoblasts do respond to irritant
  • this may build up secondary dentin, withdraw in tubule, fill with minerals etc
  • caries - dentinal tubules provide a pathway for microorganisms and other noxious substances to the pulp - pattern of caries
  • CEJ - cementum exposure - may result in dentinal exposure which may lead to additional tooth loss and/or sensitivity

Oral Sciences (8 decks)

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