Tooth Development Flashcards
When does the primary dentition develop?
embryonic and fetal period
When does the permanent dentition develop?
fetal period (tooth germs are already there)
What is odontogenesis?
tooth development
What stages occur in odontogenesis (parallel stages of facial development)
Induction, Proliferation, Differentiation, Morphogenesis, Maturation
The initiation stage involves what process?
induction between mesenchyme and ectodermal tissues to initiate tissue development
Ectomesenchyme is formed from what?
neuroectoderm; influenced by neural crest cells (NCC)
What is the importance of the NCC?
development of the face, neck, and teeth
associated with Treacher-Collins
How is the dental lamina produces
the oral epithelium grows deeper into the mesenchyme
What clinical considerations may occur during the initiation stage?
anodontia (endocrine dysfunction)
ectodermal dysplasia (excess radiation)
supernumerary
What is the second stage of odontogenesis?
Bud stage/Proliferation
What occurs during the bud stage?
extensive proliferation of dental lamina into buds/masses into the ectomesenchyme
What two structures form the tooth germ?
dental lamina + ectomesenchyme
What clinical considerations may occur during the bud stage?
macrodontia
microdontia
What is the third stage of odontogenesis?
Cap stage (proliferation, differentiation, morphogenesis)
During the cap stage, is the proliferation equal growth?
NO, unequal growth leading to cap shape
Cytodifferentiation
different cells
Histodifferentiation
different tissues
morphodifferentiation
different organs/structure shapes
all of the processes in the cap stage form the…
enamel organ (from ectoderm*)
ectomesenchyme forms the…
dental papilla first (dentin and pulp), the remaining forms the dental sac/follicle (cementum, PDL, bone)
The basement membrane between enamel organ and dental papillae will form what?
Dentinoenamel junction (DEJ)
What three structures together form the tooth germ?
enamel organ, dental papilla, dental sac/follicle
How is development of adult anterior teeth initiated?
extension of dental lamina into ectomesenchyme lingual to developing primary tooth germ
known as “successional dental lamina”
Considering adult molars are non-succadaneous, how do they form?
posterior extensions of the dental lamina distal to the primary second molar
What clinical considerations may occur during the cap stage?
dens in dente, gemination, fusion, tubercules
What is the fourth stage of odontogenesis?
Bell stage (proliferation, differentiation, morphogenesis)
During the bell stage, differentiation results in how many different types of cell within the enamel organ?
4; OEE, IEE, STR, STRI
OEE
outer enamel epithelium; protective barrier
IEE
inner enamel epithelium; produces columnar cells which are future ameloblasts (enamel secreting cells)
Stellate Reticulum (STR)
star shaped cells forming a network (cell integrity)
Stratum Intermedium (STI)
compressed cuboidal cells, help support production of enamel
The outer cells of the dental papilla will form what?
odontoblasts (dentin secreting)
The central or inner cells of the dental papilla will form what?
primordium of the pulp
What are the final stages of odontogenesis?
Apposition and Maturation
“Secretory stage”
(Induction, proliferation, maturation)
When does maturation occur?
when the matrix of dental tissues is fully mineralized
What is reciprocal induction?
induction between ectodermal tissue of enamel organ and mesenchymal tissue of dental papilla and sac
results in proliferation of cellular byproducts
What does the basement membrane do?
acts as a means of communication between the tissues, cellular interaction
What part of the bell shaped enamel organ forms the preameleoblasts?
IEE
What is reporlarization?
when nucleus of cell moves farthest away from basement membrane, this initiates odontoblasts to secret dentin, which then initiates amleoblasts to secret enamel
How are odontoblasts and the dentin matrix formed?
after IEE differentiates into preameleoblasts, outer cells of dental papilla are induced to reposition and repolarize, so odontoblasts will begin apposition of predentin (dentin matrix)
Which tooth tissue is laid down first?
dentin, than enamel (dentin slightly thicker than enamel matrix)
How are ameleoblasts formed?
basement membrane disintegrates between preameloblasts and odontoblasts, allowing contact which induces preameleoblasts to become ameleoblasts; ameleogenesis starts
What process secretes the enamel matrix?
Tome’s process; angled part of ameleoblast
What are the clinical considerations regarding enamel development?
enamel dysplasia (Hutchinson’s teeth, ameleogenesis imperfecta, dentinogenesis imperfecta
When does the root develop?
AFTER the crown is completely shaped and erupted into oral cavity
What is responsible for root development?
cervical loop
What forms the cervical loop?
OEE and IEE
How is Hertwig’s Root Sheath formed?
cervical loop grows deeper into surrounding ectomesenchyme of dental sac, elongates and moves away to enclose more of dental papilla, forming sheath
What is Hertwig’s root sheath (HERS) responsible for?
shape of roots, decides if roots are curved, single or multi-rooted
induces dentin formation in root area
How does root dentin form?
when outer cells of dental papilla undergo induction and differentiate into odontoblasts, induction occurs under influence of IEE and HERS
What causes epithelial rests of Malassez?
once root dentin is complete, basement membrane between IEE and odontoblasts disintegrate, along with sheath. Some sheath cells may become entrapped, can cause cyst or infection
How is cementum formed?
HERS disintegrates, allowing contact of root dentin with undifferentiated cells of dental sac, cementoblasts move to cover root dentin and lay down matrix (Cementoid)
As the matrix becomes mineralized, it is considered…
cementum
What forms where the basement membrane between the papilla and sac was located?
dentinocemental junction (DCJ)
What clinical consideration may occur during development of cementum?
concrescence
How are multi-rooted teeth formed?
originate as single root, root then divides into correct number of branches, differential growth of HERS cause multirooted teeth to divide into 2 or 3 roots.
Elongation of cervical loop occurs, which develops long horizontal epithelial extensions, each extension represents a root
What clinical considerations may occur during root development?
enamel pearls, dilacerations, supernumerary roots
How is the PDL and alveolar bone formed?
ectomesenchyme from dental sac forms PDL and collagen fibers, as well as mineralizes tooth socket/alveolus of alveolar bone
Active eruption
actual vertical movement of tooth
Passive eruption
occurs with aging; gingival tissue recess making tooth appear longer, but there is no actual movement
What factors may play a role in eruption?
root growth, temporary ligament, vascular pressure, contractile collage, hormone signals
active eruption is not fully understood
Explain the process of eruption
ameloblasts place accelular dental cutile on newly formed enamel, enamel organ layers compress forming REE (reduced enamel epithelium), formation of REE allows tooth to erupt, will give rise to junction epithelium
Explain the process of exfoliation
REE fuses with oral epithelium, enzymes from REE disitagrte central part of fused tissue, leaving epithelial tunnel for succedaneous tooth to erupt, coronal part of fused epithelium peels of crown, cervical part attached (created JE seal), succadenous tooth develops lingual to, osteoclasts absorb bone, odontoblasts absorb tooth tissues, and fibroblasts destroy collagen fibers
Disintagration known as “teething”
Intermittent shedding due to clast and blasts working at same time
What is the exception to permanent teeth developing lingual to shedding primary tooth?
Maxillary incisors; facially placed
Is the process the same for permanent eruption as primary teeth?
Yes; REE fuses with OE to create a tissue that disintegrates and leaves epithelial lined tunnel
What is Nasmyth’s membrane?
Residue that forms on newly erupted teeth of both dentitions, extrinsically stains
Made of OE and REE and dental cuticle
Can be removed by scaling/polishing
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