140 terms

Tooth Development and Eruption

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Tooth development
odontogenesis
What is the time span for initiation?
6th to 7th weeks
What happens during initiation?
Ectoderm lining stomodeum gives rise to the oral epithelium and then to the dental lamina, adjacent to deeper ectomesenchyme, which is influenced by the neural crest cells. Both tissues are seperated by a basement membrane
What is the time span for the bud stage?
8th week
What is the main process involved in initiation?
induction
What is the main process involved in the bud stage?
proliferation
What happens during the bud stage?
Growth of the dental lamina into bud that penetrates growing ectomesenchyme
What is the time span for the cap stage?
9th to 10th weeks
What are the processes involved in the cap stage?
proliferation, differentiation, morphogenesis
What happens during the cap stage?
Enamel organ forms into cap, surrounding mass of dental papilla from the ectomesenchyme and surrounded by mass of dental sac also from the ectomesenchyme. Formation of the tooth germ.
What is the time span for the bell stage?
11th to 12th weeks
What processes are involved in the bell stage?
differentiation, proliferation, morphogenesis
What happens during the bell stage?
Differentiation of enamel organ into bell with four cell types and dental papilla into two cell types.
What processes are involved with the apposition stage?
induction, proliferation
What happens during the apposition stage?
Dental tissues secreted as matrix in successive layers.
What happens during the maturation stage?
Dental tissues fully mineralize to their mature levels.
What is the process involved in the maturation stage?
maturation
What is the outer portion of the ectoderm in the initiation stage?
oral epithelium
What is the important acelluar structure that seperates the oral epithelium and the ectomesenchyme?
the basement membrane
The oral epithelium is induced by the ectomesenchyme to produce what?
the dental lamina
The stage named for extensive proliferation of the dental lamina into oval masses penetrating into the ectomesenchyme?
The bud stage
What else undergoes proliferation in the bud stage besides the dental lamina?
the ectomesenchyme
The buds of the dental lamina, together with the surrounding ecto mesenchyme, will develop into what?
Tooth germ
What happens to the thickened non tooth producing portions of the dental lamina eventually?
it disintegrates as the developing oral mucosa comes to line the oral cavity
In the cap stage the tooth bud does not grow, what happens?
there is unequal growth in different parts of the tooth bud
What is the predominate process of the cap stage?
morphogenesis
When does the tooth bud become a tooth germ?
in the cap stage
What are the major components of the tooth germ?
the enamel organ, dental papilla, dental sac
What is the cap in the cap stage?
the enamel organ
Where is the enamal organ originally derived from?
the ectoderm
What is the inner mass in the cap stage that forms a concavity of the enamel organ?
dental papilla
What will the dental papilla eventually form?
future dentin and pulp tissue
Where is the dental papilla originally derived from?
the ectomesenchyme, which was influenced by the neural crest cells
What is the site for the future dentioenamel junction?
the basement membrane that seperates the enamel organ and dental papilla
The remaining ectomesenchyme surrounding the outside of the enamel organ condenses into what?
the dental sac
What is another name for the dental sac?
dental follicle
What will the dental sac give rise to?
the cementum, PDL, and alveolar bone
Where is the dental sac originally derived from?
the ectomesenchyme
What is the primordium of the tooth?
the tooth germ
Where does the primordium of the permanent dentition develop?
the successional dental lamina, an extension of the dental lamina that extends out lingually to the primary tooth germs
What are succedaneous teeth?
permanent teeth formed with primary predecessors, the anterior teeth and the premolars
Which teeth are nonsuccedaneous?
the permanent molars
What is the predominate process in the bell stage?
differentiation
How many types of cells are found in the enamel organ in the bell stage?
4 types
What are the cell layers found in the enamel organ in the bell stage?
the outer enamel epithelium, the inner enamel epithelium, the stellate reticulum, and the stratum intermedium
What kind of cells occur in the outer enamel epithelium in the bell stage?
cuboidal cells
What layer serves as protection for the enamel organ?
the outer enamel epithelium
What kind of cells occur in the inner enamel epithelium?
tall columnar cells
What wll the inner enamel epithelium differentiate into?
enamel secreting cells (ameloblasts)
Which layer in the bell stage has star shaped cells?
the stellate reticulum
The stellate reticulum is located inner or outer?
outer
What kind of cells reside in the stratum intermediate?
compressed layer of flat to cuboidal cells
The stratum intermediate is located inner or outer?
inner
What are the 2 layers in the dental papilla within the concavity of the enamel organ?
the outer cells of the dental papilla and the central cells of the dental papilla
What will the outer cells of the dental lamina differentiate into?
dentin secreting cells (odontoblats)
What will the inner cells of the dental lamina differentiates into?
the primordium of the pulp
What happens during the appositional stage?
the enamel, dentin, and cementum are secreted in successive layers
What is matrix?
an extracellular substance that is partially calcified, yet serves as a framework for later calcification
What stage does the dental tissues subsequently fully mineralize
maturation
What conveys communications between the cells of the enamel organ, the dental papilla, and the dental sac allowing tissue interactions?
the basement membrane
When the inner epithelial epithelium columnar cells elongate and repolarize they differentiate into what?
preameloblasts
The preameloblasts induce dental papilla cells to differentiate into what?
into odontoblasts
What do the odontoblasts do?
dentinogenesis, which is the apposition of dentin matrix, or predentin, on the other side of the basement membrane
Do odontoblasts start their secretion of matrix before the ameloblasts?
yes, this is why the dentin is thicker in the mature tooth structure than the enamel
What causes the induction of the preameloblasts to differentiate into ameloblasts?
the disintegration of the basement membrane allows the preameloblasts to come into contact with the newly formed predentin
What is amelogenisis?
the apposition of the enamel matrix
Where is the enamel matrix secreted from by the ameloblasts?
the Tomes' process, a tapered portion of each ameloblast that faces the disintegrating basement membrane
Odontoblasts leave attached cellular extensions in the length of the predentin called what?
odontoblastic process
What are the odontoblastic processes is contained in what?
a mineralized cylinder, the dentinal tubule
What cell bodies are involved in the eruption and mineralization process but will be lost after eruption?
the ameloblasts
When does the process of root development take place?
after the crown is completely shaped and the tooth is starting to erupt into the oral cavity
What is the structure responsible for root development?
the cervical loop
What does the cervical loop consist of?
a bilayer rim that consists only IEE and OEE
What is the function of the Hertwig's epithelial root sheath?
to shape the root (or roots) and induce dentin formation in the root area so that it is continuous with coronal dentin
When root formation is completed the portion of the basement membrane disintegrates its cells may become what?
epithelial rests of Malassez
What is cementogenisis?
apposition of the cementum
When the undifferentiated cells of the dental sac come into contact with the root dentin they differentiate into what?
cementoblasts
What is the cementum matrix called?
cementoid
What are entrapped cementoblasts called?
cementocytes
How is the dentinocemental junction formed?
as a result of the apposition of cementum over dentin
What is the embryological background for enamel?
enamel organ
What is the embryological background for dentin, cementum and alveolar bone?
dental papilla
What type of tissue is enamel?
epithelial
What type of tissue is dentin, cementum, and alveolar bone?
connective
What are the formative cells for enamel?
ameloblasts
What are the formative cells for dentin?
odontoblasts
What are the formative cells for cementum?
cementoblasts
What are the formative cells for alveolar bone?
osteoblasts
What are the incremental lines for enamel?
lines of Retzuis
What are the incremental lines for dentin?
imbrication lines of von Ebner
What are the incremental lines for cementum and alveolar bone?
arrest and reversal lines
What are the mature cells for enamel?
there are none, they are lost with eruption
What are the mature cells for dentin?
only dentinal tubules with processes
What are the mature cells for cementum?
cementocytes
What are the mature cells for alveolar bone?
osteocytes
What are the resorptive cells for enamel, dentin, cementum and alveolar bone?
odontoclasts
What hard tissue is can not have tissue formation after eruption?
enamel
What hard tissue has vascularity?
alveolar bone
What hard tissue is innervated by nerves?
dentin and alveolar bone
What stage does anodontia occur?
initiation stage
What is anodontia?
absence of single or multiple teeth
What are the etiological factors for anodontia?
hereditary, endocrine dysfunction, systemic disease, excess radiation exposure
What are the clinical ramifications of anodontia?
may cause disruption of occlusion and aesthetic problems, may need partial or full dentures, bridges, and/or implants
What stage does supernumerary teeth occur?
initiation
What are supernumerary teeth?
development of one or more extra teeth
What are the etiological factors for supernumerary teeth?
hereditary
What are the clinical ramifications of supernumerary teeth?
occurs commonly between the maxillary centrals, distal to the 3rd molars and premolar region. may cause crowding, failureof normal eruption and disruption of occlusion
When does macro/microdontia occur?
bud stage
What is macrodontia?
abnormally large teeth
What is microdontia?
abnormally small teeth
What are the etiological factors for micro/macrodontia?
hereditary in localized form. endocrine dysfunction is complete
What are the clinical ramifications of micro/macrodontia?
commonly involves permanent maxillary lateral incisor and 3rd molars
When does dens in dente occur?
during the cap stage
What is dens in dente?
enamel organ invaginates into the dental papilla
What are the etiological factors for dens in dente and gemination?
hereditary
What are the clinical ramifications of dens in dente?
commonly affects the permanent maxillary lateral incisor. tooth may have deep lingual pit and need endodontic therapy
What are the developmental disturbances of the cap stage?
dens in dente, gemination, tubercle, and fusion
What is gemination?
tooth germ tries to divide
What is fusion?
union of 2 adjacent tooth germs
What are the etiological factors for fusion?
pressure on the area
What are the clinical ramifications of gemination?
large single rooted tooth with one pulp cavity and exhibits "twinning" in crown area. normal number of teeth in dentition. may cause problems in appearance and spacing
What are the clinical ramifications of fusion?
large tooth with two pulp cavities. one fewer tooth in dentition. may cause problems in appearance and spacing
What is tubercle?
extra cusp due to effects on enamel organ
What are the etiological factors of tubercle?
trauma, pressure or metabolic disease
What are the clinical ramifications?
common on permanent molars or cingulum of anterior teeth
What are the development disturbances of the apposition and maturation stages?
enamel pearl, enamel dysplasia, and concresence
What is an enamel pearl?
sphere of enamel on root
What are the etiological factors for enamel pearl?
displacement of ameloblasts to root surface
What are the clinical ramifications of enamel pearl?
may be confused as calculus deposit on root
What is enamel dysplasia?
faulty development of enamel from interference involving ameloblasts
What are the etiological factors of enamel dysplasia?
local or systemic or hereditary
What are the clinical ramifications of enamel dysplasia?
pitting or intrinsic color changes in enamel. changes in thickness of enamel possible. problems in function and aesthetics
What is concrescence?
union of root structure of two or more teeth by cementum
What are the etiological factors of concrescence?
traumatic injury or crowding of teeth
What are the clinical ramifications of concrescence?
common with permanent maxillary molars
Active eruption
the actual vertical movement of the tooth
Passive eruption
when the gingiva recedes and no actual tooth movement takes place
After the enamel apposition ceases the crown area of each primary or permanent tooth what happens?
the ameloblasts place an acellular dental cuticle on the new enamel surface
How is the reduced enamel epithelium created?
the enamel organ is compressed
What happens when the reduced enamel epithelium is created?
the primary tooth can now erupt into the oral cavity, the REE fuses with the oral epithelium, then enzymes from the REE disintegrate the central portion of the epithelial tissue leaving an epithelial tunnel for the tooth to erupt