Dental Science Embryology/Histology

the study of how living things form and develop before birth

embryology

study of microscopic tissues structure & function

histology

what are the 3 stages of prenatal development

1. germinal

2. embryonic

3. fetal

what does the germinal stage begin with

fertilization

in the germinal stage after fertilization, what happens next

zygote travels to uterus for implantation (24-36 hrs after conception)

after the zygote travels to the uterus in germinal stage what happens

cells multiply into a blastocyst that attaches to uterine wall

has 3 primary embryonic (germ) layers

blastocyte

means form specific organs/tissues

differentiate

means form body systems

integrate

when are the primary embryonic layers formed

3rd - 8th weeks of development

each primary embryonic layer is ____ and will multiply to form _____ and _____ of the body

highly specialized; specific tissues; organs

outer layer

ectoderm

enamel and lining of oral cavity

ectoderm

parts of ectoderm

i. stomodeum

ii. cleft

primitive oral cavity

i . meaning early on - NOT fully developed

stomodeum

when fusion is disturbed

cleft

the cleft will be more ___ and more ___ at 8 weeks compared to 12 weeks

anterior; severe

where (how) can cleft occur?

• uvula

• primary palate

• secondary palate

• lip

• unilateral or bilateral

what is the mesoderm made of

• dentin

• pulp

• cementum

middle germ layer

mesoderm

inner germ layer

endoderm

formation of these takes several weeks to occur

hard & soft palates

when does formation of hard/soft palates being and end

begins 5th week of prenatal development

ends 12th weeks of development

if formation of hard/soft palate process is disturbed what may result

cleft

when does tooth development begin

5 weeks prenatally

by what weeks are all primary teeth formed and permanent teeth are starting to form

week 12

weeks 9 -birth

fetal stage

growth from 1” to 20”

fetal stage

most often concerning developmental disorders are by?

genetic factors

most often concerning genetic factors

tooth and jaw size

missing teeth

anodontia

extra teeth

supernumerary teeth

larger/smaller than average teeth

macro/microdontia

tooth within a tooth

dens in dente

when 2 adjacent teeth are joined

fusion

pitting, intrinsic color change in enamel

enamel displasia

thickness of dentin is affected, intrinsic color change, many problems with function & aesthetics

dentinal dysplasia

what are 2 genetic developmental disorders

• enamel dysplasia

• dentinal dyplasia

something in the enviornment that has adverse effects

teratogens

examples of teratogens

• drugs

• alcohol

• radiation

when _____ are taken during pregnancy staining of the primary and permanent teeth can occur

tetracycline antibiotics

have been found to affect the developing child (prematurely born, low-birth weight)

toxins from periodontal disease

name for tooth formation

odontogenesis

the earliest sign of formation

initiation

what is the sign of initiation (earliest sign of formation)

band of epithelial tissue called dental lamina

connects the tooth bud to the epithelial layer

dental lamina

growth period stages

1. bud

2. cap

3. bell

proliferation

bud stage

what weeks prenatally is the bud stage

6-7 weeks

resembles a flower bud

bud stage

where is the first sign of developing teeth usually?

mandibular anterior area

don’t start developing until the baby is born

permanent 6 yr molars

don’t start developing until age 5

3rd molars

hostdifferentiation

cap stage

what weeks prenatally is the cap stage

8-9 weeks

this is where the tooth bud grows and changes shape - the cells multiply

cap stage

here a specific connective tissue is formed called the dental sac

cap stage

develops into dentin, cementum, and pulp

dental sac

extra calcified tissue

odontoma

what prenatal weeks is the bell stage

9-11 weeks

this is where the cells become fully specialized

bell stage

resembles a bell

dental organ

starts at the crown of the tooth and moves toward apex

bell stage

4 layers

bell stage

when certain anomalies can occur

bell stage

minerals are laid down to form layers of the tooth, the tooth begins to be calcified

apposition stage

dental sac begins producing enamel, dentin, cementum

apposition stage

tooth becomes visible (ends at age 21)

eruption stage

once crown and root have developed it will move ____?

vertically toward oral cavity

the final stage of the life cycle of a tooth is wearing down during normal use

attrition stage

where is enamel the thickest

cusps, incisal edges, biting surfaces

hardest material in the body

enamel

is translucent

enamel

ranges in color of enamel are caused by what?

differences in thickness and translucency of enamel & color of dentin below it

what is enamel formed by

ameloblasts

composition of enamel

• 95% minerals (hydroxyapatite, calcium, phosphorus)

• 4% water

• 1% protein

mineral found in both enamel and bone, it is lost during tooth decay process

hydroxyapatite

does not contain cells capable of repair

enamel

enamel rods AKA __?

enamel prisms

extend from surface to the DEJ, are grouped in rows

enamel rods

shaped like a fish or a keyhole, with a head and tail

enamel rods

each enamel rod is encased in a ____ and they are held together by _____

prism sheath; interprismatic substance

the prism is harder than the interprismatic substance which makes it possible to __?

acid etch

microscopic bands of light & dark, caused by enamel prisms that intertwine or change direction

hunter-schreger bands

rings (like a tree) that represent variations in how the enamel matrix was deposited during formation

lines of retzius

line of retzius that registers the shock of childbirth

neonatal lines

all primary teeth could be affected and some permanent

neonatal lines

slight ridges on cervical third that run mesiodistally

imbrication lines

makes up the main portion of the tooth

dentin

covered by enamel on the crown and cementum on the root

dentin

mineralized and harder than bone and cementum

dentin

has elastic properties which help to support enamel during chewing

dentin

what is dentin formed by

odontoblasts

begins along the DEJ and proceed inward toward the pulp

dentin

dentin is capable of ____?

growth and repair

formed before the apical foramen is completed

primary dentin

forms after completion of apical foramen, forms slowly throughout life

secondary dentin

makes pulp canal smaller

secondary dentin

formed in response to irritation or injury such as decay, dental work, recession, atrrition, or errosion

tertiary dentin

microscopic canals that contain fluid

dentinal tubules