Odontogenesis and Tooth development Flashcards
what is the periodontium made of
gingivia, periodontal ligament, cementum, alveolar bone proper
when do ectoderm/mesenchyme interactions occur
before any of the 6 stages of tooth development
what layers play an instructional role during the pre-tooth bud stage of tooth formation
ectoderm (epithelium) and mesenchyme (neural crest cells)
what does the epithelium/ectoderm do in tooth development
specifies the dental nature of mesenchyme
what does the mesenchyme do in tooth development
specifies the tooth type and nature of product produced by epithelium
what does the dental papilla differentiate into
pulp and dentin
what does the dental follicle differentiate into
PDL, cementum, and alveolar bone proper
what are the 6 stages of tooth development and what happens in each
- initiation: cellular induction
- bud stage: cellular proliferation
- cap stage: proliferation, beginning of differentiation and morphogenesis
- bell stage: proliferation, differentiation, and morphogenesis. all parts of the enamel organ are visible
- apposition: induction and proliferation. mineralized tissues grow against each other
- maturation: maturation, calcification of more proteinaceous matrices
when does initiation/induction stage occur and what specifically happens
6-7th week
-invagination of the ectoderm into the mesenchyme forms the dental lamina
when does the bud stage occur and what specifically happens
8th week
- vestibule occurs through apoptosis of mesenchyme to make room for the oral ectoderm to make the primitive gut
-proliferating oral ectoderm makes transition into dental lamina
when does the early cap stage occur and what specifically happens
9-10th week
-apoptosis results in creation of buccal vestibule
what layers form in the cap stage
-outer enamel epithelium
-inner enamel epithelium
-stellate reticulum
-dental papilla
-dental follicle
what do cells in the stellate reticulum do
supportive cells, hold shape of enamel organ
what do the cells in the dental papilla do
undifferentiated cells making their way up into the inner enamel epithelium and eventually forms pulp and odontoblasts
what does the dental follicle do
encapsulates the enamel organ and eventually forms the periodontal ligament, cementum, alveolar bone
what layers are visible in the bell stage
all layers are distinguishable and enamel organ can be differentiated
what makes up the enamel organ
outer enamel epithelium, inner enamel epithelium, stellate reticulum, stratum intermedium
what type of cells are in the outer enamel epithelium and what is their function
-cuboidal cells
-protective barrier
what type of cells are in the inner enamel epithelium and what is their function
cuboidal cells
- differentiated into ameloblasts (enamel)
what type of cells are in the stellate reticulum and what is their function
-star shaped cells forming network inside enamel organ
- supportive function in enamel production
what type of cells are in the stratum intermedium and what is their function
-compressed layer of flat cuboidal cells
-supportive function in enamel production (makes alkaline phosphatase)
what type of cells are in the dental follicle/sac and what is their function
-collagen fibers around enamel organ
- differentiate into cementum, periodontal ligament, and alveolar bone
what type of cells are in the dental papilla and what is their function
-cells nearest IEE have basement membrane separation
-outer cells differentiate into odontoblasts and inner cells differentiate into pulpal tissue
what occurs with the inner enamel epithelium in the apposition stage
IEE starts cuboidal (inactive)and becomes columnar (active)
-pre ameloblasts have receptors (fibronectin) that attract dental papilla cells (pre-odontoblasts)
what do odontoblasts and ameloblasts do in the apposition stage
odontoblasts secrete pre-dentin matrix (mantle dentin) and ameloblasts sense that and secrete enamel matrix
what happens to the enamel in the apposition stage
ameloblasts separates from basement membrane, uniform process due to alkaline phosphatase from stratum inermedium
what happens to the dentin in the apposition stage
remains attached to basement membrane, becomes dentin tubules
what is mantle dentin, what type of collagen does it have and which way are the fibrils oriented in relation to the DEJ
-first formed dentin
-30-50 um thick
-contains type 1 and 3 collagen
-collagen fibers are oriented perpendicular to the DEJ
describe active ameloblasts in the apposition stage
tall columnar cells
describe inactive ameloblasts in the apposition stage and what do they form
short columnar or elongated cuboidal cells
- at the final stage of mineralization the inactive ameloblasts of the OEE, stellate reticulum, and stratum intermedium form a membrane on the surface of the enamel called the primary cuticle
what is another term for the primary cuticle
nasmyth’s membrane
how long do roots take to completely develop after eruption and what happens to them over time
1-4 years
-the pulp chambers narrow and apical opening constricts with time
what is hertwig’s epithelial root sheath
fusion and apical extension of the outer and inner enamel epithelia
what does hertwig’s epithelial root sheath determine
the outline, shape, length of the root, it is removed before cementum is laid down
what is anodontia
total lack of tooth development (no teeth)
what is hypodontia
lack of development of one or more teeth
what is oligodontia
indicates the lack of formation of 6 or more teeth
what is hyperdontia
increased number of teeth
when does hyperdontia occur in the developmental stages
initiation stage
what is mesodens in hyperdontia
most common supernumerary tooth formation, between 8 and 9
what is odontoma
small fragments of tooth structure consisting of dentin, enamel, cementum or any combination
what is complex odontoma
comprised of a cognomina mass of enamel and dentin that bears no anatomic resemblance to a tooth. locally invasive and continue to expand, need to remove
what is compound odontoma
comprised of multiple small tooth like structures, need to remove
what is concresence
defect occuring during apposition and maturation stages that results in union of rooth structure of two or more teeth by cementum
what is tubercle formation
defect occuring during the cap stage that results in an extra cusp due to effect on the enamel organ
what is gemination and fusion
defect that originated during the cap stage of development and results in large single rooted tooth with one pulp cavity and exhibits twinning crown
what is gemination
tooth count is normal when the double tooth is counted as one
what is fusion
refers to a double tooth in which the tooth count reveals a missing tooth when the double tooth is counted as one
what is abnormal root development caused by
issue with hertwig’s rooth sheath
what is taurodontism
an enlargement of the body and chamber of multirooted teeth with apical displacement of the bifurcation (long root trunk with very short roots)
-low bifurcation
what is a dilaceration
bend in the root, abnormal angulation
what is a dentigerous cyst caused by
separation of the dental follicle from the crown of an unerupted tooth
where are dentigerous cysts attached
at the CEJ
where are odontogenic keratocysts most common
mostly in posterior mandible
what do odontogenci keratocysts arise from
the cells rests of the dental lamina (rests of serres)
what percentage of odontogenic cysts do odontogenic keratocysts account for and what is the recurrence rate
3-11% with 30% recurrence rate
describe the cysts in odontogenic keratocysts
consists of 6-8 cell layers of stratified squamous epithelium with parakeratosis at the luminal surface
what is an ameloblastoma and what does it look like on a radiograph
slow growing and locally invasive tumor, lesions appear a multilocular or soap bubble and radio-resistance
what is the most common neoplastic lesion arising from odontogenic epithelium
ameloblastoma
