Teeth 2

What are the stages of the ameloblast life cycle?

1. Morphogenetic stage epithelial cell (centered nuclei) 2. Differentiation (nuclei apical) 3. Initial secretory stage 4. Secretory stage (using Tomes process, no more basal lamina proteins synthesized) 5. Maturation stage with ruffle end (with basal microvilli) 6. Maturation stage with smooth end 7. Protective stage (ameloblasts protect until apoptosis prior to tooth eruption)

Cementoblasts arise from two sources 1. 2.

1. epithelial cells from HERS 2. CT of the dental follicle

Amelogenesis has two steps 1. 2.

1. synthesize enamel with partially mineralized matrix (~30% mineral) 2. remove organic molecules and water to form high mineralized matrix (96% mineral)

What are the tooth development stages?

1. thickening (dental lamina --> placode) 2. bud 3. cap 4. bell 5. apposition 6. maturation

_____________ zone is where the first predentin is deposited form mantle dentin.

Acellular

_____________________ is synthesis of dentin and enamel strating int he crown and sythesis of cementum later in the root.

Apposition

What stage of tooth formation does this occur? Cytodifferentiation forms inner and outer epithelium of the enamel organ, stratum intermedium, stellate reticulum

Bell

To form the root, the inner and outer dental epithelia grow to form a two-layered ____________ _________ _________ _________ with NO stratum intermedium and NO stellate reticulum

Hertwig's epithelial root sheath

Does a basal lamina separate odontoblasts from pulp?

NO, odontoblasts are not epithelium.

Which comes first? Odontoblasts synthesize dentin Inner enamel epithelium becomes ameloblasts

Odontoblasts secrete dentin

Which is the major load bearing area of the enamel? The rod or interrod?

Rod (parallel to long axis rods)

Ruffle/smooth end ameloblasts transport peptides amino acids and water OUT of matrix. This process is called matrix reduction/hypermineralization

Smooth matrix reduction

Incremental growth of enamel (~4um) every 24 hours creates __________ __ ___________

Striae of Retzius

Which zone is only present in tooth development? Throughout life?

acellular zone (space where predentin is secreted to form mantle dentin) cell-free zone (layer beneath odontoblasts towards pulp)

Holes are formed in enamel because rod enamel is formed before/after interrod enamel

after

The dental follicle forms the cementum (cementoblasts), PDL (fibroblasts), and ______________ _______ (osteoblasts)

alveolar bone

If there is no odontoblasts formed, the simple columnar layer of cells is NOT _________________. Instead it is called ______________ ______________ _________________

ameloblasts inner dental epithelium

Preameloblasts reverse polarity to become secretory ameloblasts, which have nuclei located at the apical/basal side

apical

The Tome's process is an apical/basal structure

basal

The future crown is formed in the ______ stage. _____________ ________ form the future cusps

bell stage Enamel knots

Morphogenesis occurs in what stages? Cytodifferentiation? Induction?

bud and cap cap and bell thickening/placode

What stage of tooth formation does this occur? Cytodifferentiation forms an enamel organ of epithlial cells and a dental papilla of mesenchymal cells

cap

Remnants of HERS persist as ______ ______ __ ________________

cell rests of Malassez

Dental follicle cells in contact with the outer surface of dentin on HERS will differentiate into ______________

cementoblasts

Cementoblasts form __________ on dentin, forming the DCJ Cells in lacunae become __________________

cementum cementocytes

Fibroblasts and other cells of the PDL differentiate from cells of the ________ ____________ around the tooth

dental follicle

Is the basal lamina next to the stellate reticulum or by the dental papilla?

dental papilla

The proximal/distal part of the Tome's process makes the rod enamel, first/second

distal second (to fill the whole formed by interrod enamel)

The growth fronts of enamel rods are slanted due to the angle of the __________ part of the Tome's processes

distal part

Each ameloblast is connected by junctional complexes at the ____________ ___________ ______

distal terminal web

___________ will form the dental lamina that gives rise to ameloblasts (AN EPITHELIUM)

ectoderm

_____________ --> enamel organ ----> cervical loop --> HERS --> _____________ ---> cementum

ectoderm cementoblast

_____________ --> enamel organ --> inner enamel epithelium --> ____________ --> enamel

ectoderm ameloblast

Neural crest cells differentiate into __________________, which becomes the dental papilla

ectomesenchyme

Remnants of the dental lamina after it has separated from the tooth germ are called

epithelial pearls

Secretory ameloblasts synthesize the full thickness/partial thickness of enamel before maturation begins

full thickness

Neural crest mesenchyme undergoes condensation and ___________ proliferation and outgrowth of ectodermal cells to form the tooth bud.

induces

Which enamel epithelium layer is in contact with basement membrane?

inner dental epithelium

The stratum _________________ supports ameloblast metabolism since it is an epithelial layer without vessels

intermedium

Note the cross section appearance of Tome's processes Newly formed enamel has a honeycomb pattern caused by basophilic staining of ________ ___________, which will form interrod enamel

interrod substance

Why is pre-enamel not observed in histological slides?

it is QUICKLY mineralized

The basal ends of adjacent ameloblasts are held together by _____________ complexes

junctional

Step 2 of amelogenesis involves secretory/maturation ameloblasts removing water and proteins to increase mineralization of enamel

maturation

______________ is completion of the tooth tissue formation (hard and soft) and tooth eruption

maturation

Secretory vesicles fuse with the plasma membrane of the Tome's process to release enamel proteins on the basal side of the ameloblast using a ______________ mechanism

merocrine

_______ _________ --> dental follicle --> PDL

neural crest

_________ _________ --> dental papilla ---> pulp

neural crest

_____________ ____________ mesenchyme --> dental papilla ---> ________________ ---> dentin

neural crest odontoblast

_____________ _________ _________________ deep to the dental lamina will form odontoblasts (NOT AN EPITHELIUM)

neural crest mesenchyme

_________ ___________ --> dental follicle --> ______________ --> cementum

neural crest mesenchyme cementoblast

Remember that NOT all of the mesenchymal cells in the dental papilla differentiate to form _________________

odontoblasts

The Hertwig's epithelial root sheath (HERS) secretes factors that induce pulp cells to differentiate into ________________ but not ______________ because no stratum intermedium is present to support them or signal their differentiation.

odontoblasts ameloblasts

The enamel organ contains

outer enamel epithelium, inner enamel epithelium, stellate reticulum, stratum intermedium

The proximal/distal part of the TOme's process makes the interrod enamel, first/second

proximal first

What organelles do ameloblasts have ample amounts of?

rER and Golgi (for active secretion of preenamel proteins)

Neural crest mesenchyme of the dental papilla in the cap stage is _____________ _______________ by ectodermal cells to begin to differentiate into odontoblasts

reciprocally induced

The edge of the distal portion of the Tome's process forms the _____ __________

rod sheath

The HERS forms the tooth _____ and turns inward at the cervical loop to form the tooth apex.

root

Ruffle/smooth end ameloblasts transport ions (Ca PO4) and proteases INTO matrix This is done using the Tome's process/basal microvilli This process is called matrix reduction/hypermineralization

ruffle basal microvilli hypermineralisation

Step 1 of amelogenesis involves secretory/maturation ameloblasts synthesizing partially mineralized enamel containing mostly enamel proteins (amelogenins), other organic components and water.

secretory

Enamel knots are associated with which part of the enamel organ?

stratum intermedium

The Tome's process is just the projection/the whole basal end of the ameloblast

the whole basal end

Bud + mesenchyme = _______ ______

tooth germ

Predentin matrix include type __ collagen, dentin phosphoprotein (DPP), dentin sialoprotein (DSP), osteopontin, osteocalcin, osteonectin, bone proteins, PGs, procollagen producing enzymes.

type 1 collagen (LIKE BONE)