Oral Histo M2 Odontogenesis

process of tooth formation

Odontogenesis

definition of: 1. Odont 2. Genesis

1. signifying teeth or tooth 2. formation

Liver grows then function to __________ different substances \n Bone grows then function serves as __________ in body \n Tooth grows then _________ and __________

metabolize \n storage of calcium \n calcifies and erupts

lined by oral ectoderm (stratified squamous epithelium)

Primitive oral cavity or stomodeum

Oral ectoderm contacts endoderm of foregut to form __________

buccopharyngeal membrane

Most of connective tissue cells underlying oral ectoderm are __________ or __________ in origin

neural crest or ectomesenchyme

At about __________ of gestation, the buccopharyngeal membrane ruptures and the primitive oral cavity establishes the connection with foregut

27th day

After about __________ of development, a continuous band of odontogenic epithelium forms around the mouth in the presumptive upper and lower jaws

37 days

__________ are roughly horseshoe shaped and correspond in the position of future dental arches of upper and lower jaws

Primary epithelial brands

Key feature of initiation of tooth development

formation of localized thickening or placodes within primary epithelial band

placodes are morphologically similar to dental placodes which initiates

the development of other ectodermal appendages

Definition of:

1. Placodes

2. Appendages

1. localized thickening

2. elevated parts from origin of body

2 subdivisions of primary epithelial band

dental lamina and vestibular lamina

which forms first, dental lamina or vestibular lamina?

dental lamina

what happens after 2 or 3 weeks after rupture of buccopharyngeal membrane, when the embryo is about 6 weeks old?

certain areas of basal cells of oral ectoderm proliferate more rapidly than do the cells of adjacent areas

proliferation of cell leads to formation of __________, which is a band of epithelium that has invaded the underlying ectomesenchyme along each of horseshoe-shaped future dental arches

dental lamina

Dental lamina serves as __________ of the ectodermal portion of deciduous teeth

primodium

Definition of:

1. Vestibule

2. Primodium

1. portion of bounded lip, cheek, teeth, and gingiva

2. first recognizable stage in embryonic development

Dental lamina represents

first sign of tooth development

First sign of human tooth development occurs at about __________

6 weeks or 6th and ½ weeks of embryonic life

Later, during development of jaws, the permanent molars arise directly from __________

distal extension of dental lamina

__________ is responsible for location of germs of permanent molars in the ramus of mandible and tuberosity of maxilla

Distal proliferation of dental lamina

Definition of:

1. Germ

2. Vestibular

1. primitive embryo or any part of it which will develop into separate organ

2. lies between cheeks and lips

Development of first permanent molar is initiated at __________

fourth month in utero

Successors of deciduous teeth develop from __________ opposite to the enamel organ called successional lamina and develops from __________

lingual extension of free end of dental lamina fifth month in utero to tenth month of age

Dental lamina grow backwards and giving rise to further __________ (10-week embryo), and the __________ (first permanent molar at 16-week embryo; second and third permanent molars after birth)

enamel organs for second deciduous molar permanent molars

Fate of dental lamina

1. Activity over at least 5 years

2. all disappear (no more connection), except in third molar region and occasional epithelial remnants

3. break up with mesenchymal invasion which, is at first incomplete and does not perforate the total thickness of lamina

Labial and buccal to the dental lamina in each dental arch, another epithelial thickening develop independently called __________

vestibular lamina or lip furrow band

Vestibular lamina hallows and forms the oral vestibule between __________ and __________

alveolar potion of jaws and lip and cheeks

Along the dental lamina, each representing the location of __________ and _, the ectodermal cells multiply still more rapidly and form _ that grows into underlying mesenchyme

10 mandibular and 10 maxillary deciduous teeth little knobs

Each of little outgrowths from dental lamina represents __________

beginning of enamel organ of tooth bud of deciduous tooth

T or F Not all these enamel organs start to develop at the same time

True

Where does the first tooth development appear?

mandibular anterior region

T or F Shape and size of individual teeth are different

True

T or F They does not pass through similar stages of development

False (They pass through similar stages of development)

The area named after shape of epithelial part of __________

tooth germ

Definition of:

1. Tooth germ

2. primodium

1. earliest evidence of tooth

2. first recognizable stage in embryonic development

Nolla's Stages of Tooth Formation

Presence of crypt

Initial calcification \n ⅓ of crown completed \n ⅔ of crown completed \n Almost completed \n Crown completed \n ⅓ of root completed \n ⅔ of root completed \n Root almost completed (open apex) \n Apical end of root completed

Explain Initiation Stage/Bud Stage

1. Epithelium is separated from underlying ectomesenchyme by basement membrane

2. Simultaneous with differentiation of each dental lamina, premodia od enamel organ arise from the basement membrane at 10 different points (future deciduous teeth)

3. bud stage initiate as ectodermal cells continue to proliferate

round or ovoid swellings at bud stage

primodia of enamel organ (tooth buds)

give rise to enamel tissue

Enamel organ/dental organ

Main function of certain epithelial cells of tooth bud

to form the tooth enamel, these cells constitutes the enamel organ, which is critical to normal tooth development

Many cells of tooth bud and surrounding mesenchyme undergo __________ resulting to ___________ of neural crest cells into ectomesenchyme cells surrounding the tooth bud condense

mitosis

migration

area of ectomesenchymal condensation immediately subject to enamel organ

dental papilla

form dentin and pulp

Cells of dental papilla

Condensed ectomesenchyme that surrounds tooth bud and dental papilla

dental sac

Both dental papilla and dental sac become more well defined as __________

the enamel organ grows into cap and bell shapes

form cementum and periodontal ligament

Cells in dental sac

Three parts of tooth bud

Dental organ/enamel organ

Dental papilla \n Dental sac/dental follicle

Derived from oral epithelium will produce enamel

Dental organ/enamel organ

Derived from mesenchyme will produce pulp and dentin

Dental papilla

Derived from mesenchyme will produce cementum and periodontal ligament

Dental sac/dental follicle

process of ectoderm

dental organ/enamel organ → oral epithelium → ameloblasts → enamel

process of Ectomesenchyme

dental papilla → connective tissue → odontoblast → dentin and pulp

process of Ectomesenchyme

dental sac/dental follicle → connective tissue → cementum and periodontal ligament

Explain Proliferation Stage/Cap Stage

1. tooth bud continues to proliferate, no uniformed shpere expand

2. Instead, unequal growth in different part so tooth bud leads to cap stage, which is characterized by shallow invagination on deep surface of bud

layers of cells seen in early cap stage

outer enamel epithelium

inner enamel epithelium \n stellate reticulum

peripheral cells of cap stage and cuboid in shape that cover the convexity of cap

Outer enamel epithelium

columnar cells in concavity of of cap

Inner enamel epithelium

polygonal cells located in center of enamel organ, between outer and inner enamel epithelium, begin to separate as more intercellular fluid is produced and form stellate reticulum

Stellate reticulum (enamel pulp)

Accessory or temporary structures during cap stage

enamel knot

enamel cord

cells in center of enamel organ that projects in part toward the underlying dental papilla, so that the center of the epithelial invagination shows a knoblike enlargement

Enamel knot (knob-like enlargement)

function of enmel knot

to act as a reservoir of dividing cells for growing enamel organ

vertical extension of enamel knot

enamel cord

function of enamel

to act as a reservoir of dividing cells for growing enamel organ

Both enamel knot and enamel cord temporary structures that disappear before __________

enamel formation begins

Under the organizing influence of proliferating epitelium of enamel organ, the ectomesenchyme (neural crest cell) that is partially enclosed to inner epithelium proliferates and condenses to form __________

dental papilla

formative organ of dentine and pulp

dental papilla

Basement membrane that separates the enamel organ and dental papilla just prior to dentin formation

membrana preformative

future DEJ

membrana preformative

Concomitant with development of enamel organ and dental papilla, there is a marginal condensation in ectomesenchyme surrounding enamel organ and dental papilla

dental sac

Denser and more fibrous dental sac or dental follicle develops which is important in

formation of cementum and periodontal ligament

Explain Histodifferentiation stage (bell stage)

1. Boundary between inner enamel epithelium and odontoblasts outlines future dentinoenamel junction

CT cells that develop into dentin

odontoblast

Basement membrane that separates enamel organ and dental papilla just prior to dentin formation

Membrana performativa (future dentinoenamel junction)

Cervical portion of enamel organ gives rise to __________

epithelial root sheath of Hertwig

It helps the development of roots begins after enamel and dentin formation has reached future CEJ

HERS

Enamel organ plays an important role in root development by forming __________

HERS that molds shape of roots and initiates radicular dentin formation

HERS consists of

inner epithelium and outer epithelium

Root formation begins after outline of crown has been established, but before __________

full crown is calcified

area where outer and inner enamel epithelium come together. This point is where cells continue to divide until tooth crown attains its full size and which after crown formation will give rise to epithelium for root formation

Cervical loop (zone of reflexion)

In root formation, inner enamel epithelium remain short and does not produce __________

enamel

these cells included differentiation of radicular cells into odontoblasts and the first layer of dentin has been laid down

enamel epithelium

this loses its structural continuity and its close relation to surface of root

HERS

persist as an epithelial network of strands near external surface of root

Remnants of HERS

Remnants that are found in periodontal ligament of erupted teeth

rests of Malassez

There is pronounced difference in development of HERS in ____________

one root and those with two or more roots

Prior to beginning of root formation, the HERS forms

epithelial diaphragm

Inner and outer epithelial end at __________

future EDJ into horizontal plane, narrowing wide cervical opening of tooth germ

it remains relatively fixed during development and growth of root

Horizontal plane of diaphragm

accompanied by proliferation of cells of connective tissue of pulp which occurs in area adjacent to diaphragm

Proliferation of cells of epithelial diaphragm

Free end of diaphragm does not grow into connective tissue but epithelium proliferates __________

coronal to epithelial diaphragm

explain morphodifferentiation stage (structure and stage)

1. Basic form and relative size of future tooth is established

2. DEJ and DCJ are characteristic for each type of tooth, acts as blueprint pattern

3. With this pattern, the ameloblasts, odontoblasts, and cementoblasts deposit enamel, dentin and cementum, and give complete tooth

Disturbances in morphodifferentiation may affect

form and size of tooth without impairing function of ameloblasts and odontoblasts

explain Apposition stage

1. Deposition of matrix of hard dental structures

2. Appositional growth is characterized by regular and rhythmic deposition of cellular matrix

3. Appositional growth of enamel and dentin is layer-like deposition of extracellular matrix

4. This type of growth is additive

5. Fulfillment of plans outlined at stages of histodifferentiation and morphodifferentiation

Process by which organic tissue, that is matrix formed during apposition becomes hardened by deposit of calcium or any mineral salts within its substance

Calcification period

Process through which forming tooth comes into and tires to main occlusion This phase continues throughout lifetime of tooth

eruption period