Tooth Development Flashcards
What represents the beginning of odontogenesis?
The appearance of dental lamina arising from the oral epithelium
Adontia, stage?
Congenital absence of ALL teeth
Associated with Ectodermal Dysplasia
During initiation
Partial Adontia, Stage?
Hypodontia (1-5 teeth missing)
Oligodontia (>6 teeth missing)
Developmental disturbance with dental lamina formation
No tooth germs
Max latereal incisors are the most common to be missing
During initiation
Hyperdontia (Polydontia), stage?
Extra teeth permamnent dentition Mesiodens, common example Extra tooth germ is formed During Initiation
Primary Epithelial band formation
Thickened epithelium (ectoderm) in place of future jaws Rapid cell division gives rise to 2 subdivisions dental lamina and vestibular lamina
Bud Stage
Oral epithelium invaginates into the ectomesenchyme which will condensate
What does dental lamina rise from?
Ectoderm lining of stomadeum –> oral epithelium –> dental lamina
What influences the ectomesenchyme?
Neural crest cells
Lateral lamina
Tethers the bud of dental lamina
Cap stage
Epithelial outgrowth of enamel orga forms cap over ectomesenchyme
Bud–> Enamel organ
Ectomesenchyme–>Dental Papilla
Dental follicle surrounds the enamel organ and dental papilla
Inner enamel epithelium become ameloblasts
Degeneration of the vestibular lamina gives rise to what structures
(Cap stage)
Epithelial lining for Oral vestibule Alveolar mucosa Parts of gingival mucosa Inner lip mucosa Mucosal space btw the cheeks or lips
Dens in dente, what stage?
Tooth within a tooth
Enamel organ expands more than it should and invaginates into the dental papilla
During cap stage
Fusion, stage?
Union of 2 teeth by dentin and enamel
Fewer number of teeth
Extra wide crown with 1 pulp cavity
During Cap stage
Gemination, stage?
1 tooth attempting to divide, abnormally wide crown, incomplete
Correct number of teeth
During Cap stage
Bell Stage General
Deepening of the undersurface
Morphodifferentiation
Histodifferentiation
Dental lamina disintegrates
Morphodifferentiation
Occurs during Bell stage
Enamel organ takes on the shape of an incisor, canine, or molar
Histodifferentiation
During bell stage
Ameloblasts (enamel) and odontoblasts (dentin) acquire their phenotype
Tooth germ consists of
Enamle organ, dental lamina, dental papilla
Bell Stage In depth
Dental lamina disintegrates
Tooth continues to develop separate from the oral epithelium
Crown pattern established
Stellate reticulum thin over cusp tip
Stratum intermedium assists ameloblasts and nourishes them
Early Bell Stage
Histodifferentiated enamel organ (cervical loop region) is supported by basal lamina around periphery
Development of Succedaneous Teeth
Proceed through all the same stages of odontogenesis as primary teeth do
Permanent Molar development
Posteriormost extent of dental lamina does not disintegrate, elongates in a posterior direction giving rise to 12 buds –> permanent molars
Incisors, canines, and premolar development
Form due to further proliferative activity within the dental lamina
On lingual aspect of deciduous tooth germ
Dental Papilla cells
Peripheral cells of papilla face Inner enamel epithelium and differentiate into odontoblasts which secrete dentin
Inner cells of dental papilla form pulp
Dental Follicle Cells
Inner cells closest to the enamle organ become cementocytes and form cementum
Outer cells form PDL and contribute to alveolar bone formation
Which 2 cells help in formation of enamel?
Stratum intermedium and Inner enamel epithelium
Cervical Loop region/Zone of Flexion of the Enamel Organ
Hertwigs Epithelial Rooth Sheath (HERS) joining of IEE and OEE
Initiates root formation
Gives rise to epithelial component of root after crown is formed
Cervical Loop cont.
Rapid cell division within cervical loop Enamel organ elongates Depth of the concavity increases and enamel organ resembles bell Crown joins the root Enamel joins the cementum
Crown pattern Development
Pattern and number of cusps is establishedby complete folding of the IEE (morphodifferentiation)
What causes folding of IEE?
Intrinsic growth caused by differential rates of mitotic division within the IEE
Stellate reticulum over cusp tips is reduced
Epithelial Pearls or Rests of Serres
Fragmentation of dental lamina results in discrete clusters of epithelial cells surrounded by connective tissue and normally degenerate
Some are phagocytosed
If they persist they are deemed Epi Pearls/ Rests of Serres
What could Epithelial Pearls form?
Eruption cysts- cells form over developing tooth and delay eruption
Odontomes, or activated to form supernumerary teeth
Cusp Development
Growth center- point at which IEE cell differentiation first occurs –> site of future cusp development
A 2nd xone of differentiation within IEE leads to second cusp and so on
Enamel Knot (Ahrens Knot)
Embryonic signaling center- provides positional info for tooth morphogenesis
Ectomesenchymal cells of papilla induce cells of knot to express signaling molecules
Know cells control folding of IEE (cuspal morpho)
Incisors have 1 know Molars have multiple
Knots undergo apoptosis
Enamel Cord
Associated with the placement of the 1st cusp
Also called enamel septum
Microdontia, stage?
Small teeth
Max incisors and 3rd molars often affected
Peg lateral
During Bell stage
Macrodontia, stage?
Large teeth
Uncommon, associated with Hemifacial Hypertrophy
Amelogenesis Imperfecta, stage?
Hereditary, enamel formation disorder
Dentinogenesis Imperfecta
Hereditary affects dentin
Clear yellow grey teeth
