Oral Development

Front 1

what day does caudocephalo folding begin?

Back 1

day 24

Front 2

on which day does the embryo complete folding?

Back 2

day 28

Front 3

which 2 plates is the stomatodeum bounded by?

Back 3

neural and cardiac

Front 4

the stomatodeum is separated from the gut by which membrane?

Back 4

buccopharyngeal membrane

Front 5

what is the first event in the development of face? (4th week)

Back 5

disintegration of buccopharyngeal membrane

Front 6

what does the disintegration of the buccopharyngeal membrane allow?

Back 6

allows the stomodeum to increase in depth

Front 7

define stomadeum

Back 7

a shallow depression in embryonic surface ectoderm

Front 8

what initiates development of the face?

Back 8

formation of the stomadeum

Front 9

what gives rise to the oral epithelium (primitive two- or three-cell thick layer of epithelium) that covers an embryonic connective tissue?

Back 9

stomadeum

Front 10

dental lamina develops from?

Back 10

oral epithelium

Front 11

at which week does odontogenesis begin?

Back 11

week 6

Front 12

what 3 events are included in odontogenesis?

Back 12

initiation, morphogenesis, and differentiation of component cells

Front 13

odontogenesis requires which 2 types of tissues?

Back 13

oral epithelium (dental lamina) and ectomesenchyme

Front 14

which tissues are considered hard or mineralized tissue?

Back 14

enamel, dentin, cementum

Front 15

what are the soft tissues in a tooth?

Back 15

PDL(periodontal ligament) and pulp

Front 16

when does permanent teeth begin to form?

Back 16

at birth

Front 17

define mesenchyme

Back 17

undifferentiated loose connective tissue derived from mesoderm

Front 18

define ectomesenchyme

Back 18

undifferentiated loose connective tissue AND cranial neural crest cells (of ectoderm origin) that have migrated into pharyngeal arch 1

Front 19

what does the secretion of growth factor by the dental lamina induce?

Back 19

the expression of transcription factors that leads to differentiation of the ectomesenchyme

Front 20

what are 2 transcription factors expressed by ectomesenchyme early in tooth formation?

Back 20

MSX 1 and PAX 9

Front 21

does tooth agenesis affect permanent dentition more frequently or primary teeth?

Back 21

permanent dentition

Front 22

define variable expressivities

Back 22

suggests that other genetic modifiers and environmental factors may be involved in tooth agenesis

Front 23

what is MSX 1 associated with?

Back 23

human nonsyndromic premolar agenesis

Front 24

point mutations in PAX 9 is associated with tooth agenesis in which teeth?

Back 24

posterior teeth

Front 25

name the genetic mutation in which nucleotides are replaced in a DNA sequence.

Back 25

missense

Front 26

what is a nonsense mutation?

Back 26

premature protein chain termination

Front 27

what is the horse-shoe shaped band of epithelial cells formed by mitotic activity of the continuous band of epithelium (ectodermal)?

Back 27

dental lamina

Front 28

what is the dental lamina surrounded by?

Back 28

neural-crest derived ectomesenchyme of the mandibular and maxillary arches.

Front 29

the dental lamina is separated from the ectomesenchyme by a ....?

Back 29

well-defined basal lamina

Front 30

each band of epithelium gives rise to which two subdivisions?

Back 30

dental lamina (which forms first) and the vestibular lamina (which forms shortly after and is positioned just in front of the dental lamina)

Front 31

what signifies the start of odontogenesis?

Back 31

the appearance of the dental lamina

Front 32

congenital absence of ALL teeth is called?

Back 32

andontia

Front 33

what is andontia frequently associated with?

Back 33

ECTODERMAL DYSPLASIA (a defect in the development of all ectoderm-derived tissues of the body)

Front 34

what are the 2 subcategories of partial andontia?

Back 34

hypodontia (1-5 teeth missing) and oligodontia (>6 teeth missing)

usually caused by developmental disturbance with dental lamina formation, where tooth germs are not developed.

Front 35

define hyperdontia(polydontia)

Back 35

extra/supernumery tooth (teeth)

most common in permanent dentition

Front 36

what is the most common hyperdontia?

Back 36

mesioden (tooth between the two max central incisors)

Front 37

what is hyperdontia caused by?

Back 37

developmental disturbance in dental lamina formation, where an extra tooth germ is formed --the dental lamina "settles" back down on ecotomesenchyme

Front 38

odontogenesis is initiated first by factors resident in the FIRST ARCH EPITHELIUM influencing ectomesenchyme but that with time the potential is assumed by the _____________ on the _______ day

Back 38

ectomesenchyme, 12th

Front 39

a tooth is formed from the combination of ____________ expanded from the neural folds and _______________ but NOT from combination with limb bud epithelium

Back 39

neural crest cells, mandibular epithelium

Front 40

does epithelium from other sources, such as a limb bud or the second arch lead to tooth development?

Back 40

no

Front 41

incisor epithelium combined with molar mesenchyme becomes ______________

Back 41

molar

Front 42

molar epithelium combined with incisor mesenchyme becomes ____________

Back 42

incisor

Front 43

Mesenchymal components posses a "determining influence" meaning?

Back 43

they can direct and alter the fate of the epithelium

Front 44

When is the earliest histologic indication of tooth development seen?

Back 44

day 11 of embryogenesis

Front 45

what is the sign of the earliest histologic indication of tooth development?

Back 45

thickening of the epithelium on the oral surface of the first branchial arch

Front 46

what are the 2 earliest mesenchymal markers detected during tooth development and when is it detected?

Back 46

Lhx-9 and Lhx-7 on day 9 from oral epithelium

Front 47

mutations in ONE COPY of huamn ______ gene can result in molar hypodontia

Back 47

PAX-9

Front 48

there will be no ________________ if its primary predecessor was missing

Back 48

permanent tooth

Front 49

one mutated copy of ____________ results in CLEIDOCRANIAL DYSPLASIA (failure of teeth eruption due to defective resorption of primary teeth and bone, heavy fibrous gingiva, and supernumerary teeth).

Back 49

Cbfa-1 (Runx-2)

Front 50

the following describes which model of tooth type determination:
factors responsible for tooth shape reside within the ectomesenchyme in distinct graded and overlapping fields for each tooth family.

Back 50

field (homeobox code) model

Front 51

in the field model, each of the fields expresses differing and overlapping combinations of patterning _____________

Back 51

homeobox genes

Front 52

in the field model, is there one specific gene for each tooth type?

Back 52

no

Front 53

which tooth type determination model is the following found in:

redundancy in gene function reflects its importance

Back 53

field/homeobox

Front 54

what is the clone model of tooth type determination?

Back 54

each tooth class is derived from a clone of ectomesenchymal cells programmed by epithelium to produce teeth in a given pattern

Front 55

in the clone model, the ______________induces the dental lamina to being tooth development. The clone and dental lamina progress__________

Back 55

molar clone ectomesenchyme, posteriorly

Front 56

the initiation of tooth formation starts around the ________ day of gestation.

Back 56

37th

Front 57

Name the 6 morphological stages of tooth development

Back 57

bud stage, cap stage, bell stage, apposition stage, root formation stage, eruption stage

Front 58

what three things occur during bud stage?

Back 58

incursions of the dental lamina
condensation of ectomesechymal tissue,
abnormalities (microdontia, macrodontia)

Front 59

bud stage is represented by.....

Back 59

the first epithelial incursion (dental lamina) in to the ectomesenchyme of the jaw

Front 60

during the bud stage, epithelial cells shows (little or a lot) of change in shape or function?

Back 60

little, if any

Front 61

what do core cells look like and how are they arranged?

Back 61

stellate shaped and loosely arranged

Front 62

what do peripheral cells look like? (bud stage)

Back 62

cuboidal

Front 63

the supporting ectomesenchymal cells are packed closely beneath and around______________________ (bud stage)

Back 63

the epithelial bud

Front 64

the ectomesenchymal cells are separated from the bud by what? (bud stage)

Back 64

basement membrane

Front 65

what is underneath the thickened dental lamina? (bud stage)

Back 65

condensation of the ectomesenchymal cells

Front 66

during the bud stage, what interaction leads to the formation of a series of epithelial outgrowths (placodes) into the ectomesenchyme at sites corresponding to the positions of the future deciduous teeth?

Back 66

interaction between dental lamina and the neural crest-derived ectomesenchyme of the dental papilla

Front 67

what are three other names for tooth germs?

Back 67

tooth buds, dental buds, tooth primordia

Front 68

which teeth are most commonly affected by microdontia?

Back 68

maxillary lateral incisors and third molars

Front 69

macrodontia of single teeth is relatively uncommon and often associated with _________________________

Back 69

hemifacial hypertrophy (half of the face is enlarged)

Front 70

what are the three layers of the enamel organ that signifies cap stage?

Back 70

outer enamel epithelium (OEE), stellate reticulum(SR), inner enamel epithelium (IEE)

Front 71

transition from bud to cap stage marks the onset of ____________ differences between tooth germs that give rise to different _________of teeth

Back 71

morphologic, type

Front 72

at the early cap stage, epithelial bud proliferate into ectomesenchyme, and cellular density increase immediately adjacent to the epithelial outgrowth. this is known as?

Back 72

condensation of the ectomesenchyme

Front 73

during the cap stage, the developing tooth is tethered to the dental lamina by an extension called the ___________

Back 73

lateral lamina

Front 74

what forms the "cap" over condensed ectomesenchyme?

Back 74

epithelial outgrowth (enamel organ)

Front 75

dental papilla extends around the rim of the enamel organ to form what?

Back 75

dental follicle

Front 76

which three things constitute the tooth germ?

Back 76

enamel organ, dental papilla, dental follicle

Front 77

what does the enamel organ give rise to during the cap and bell stages of development?

Back 77

distinct cell layers

Front 78

what do cells in the core of the enamel organ produce?

Back 78

proteoglycans

Front 79

cells in the enamel organ remain in contact through long processes via desmosome but are pushed apart due to viscosity in the extracellular fluid forming _____________

Back 79

stellate reticulum

Front 80

what kind of cells make up the OEE?

Back 80

squamous to low cuboidal

Front 81

what kind of cells make up the IEE?

Back 81

cuboidal to low columnar

Front 82

what is the cervical loop?

Back 82

where OEE and IEE meets and represents the presumptive cervix of the future tooth

Front 83

a condensation of ectomesenchymal cells located next to the enamel organ but separated by a basement membrane is the ___________

Back 83

dental papilla

Front 84

the dental papilla becomes what part of the tooth?

Back 84

pulp

Front 85

which cells are responsible for dentinogenesis?

Back 85

peripheralmost cells

Front 86

these cells of the dental papilla are the cells facing IEE and differentiate into odontoblasts and secrete dentin.

Back 86

peripheral cells

Front 87

the _______ cells of the dental papilla will form the pulp

Back 87

inner

Front 88

mass of fine speriodic fibrils extends into an ______________

Back 88

acellular zone (First secreted enamel matrix proteins accumulate)

Front 89

what is the ectomesenchymal structure that is LESS CELLULAR and MORE FIBROUS than the dental papilla?

Back 89

dental follicle (sac)

Front 90

what does the dental follicle (sac) surround and what separates it from the enamel organ?

Back 90

surround enamel organ and dental papilla. separated by basement membrane

Front 91

the dental follicle (Sac) has more _________________ than dental papilla in the extracellular spaces between fibroblasts.

Back 91

collagen fibrils

Front 92

inner cells of the dental follicle closest to the enamel organ become ___________ and produce _______________

Back 92

cementocytes, cementum

Front 93

outer cells of the dental follicle forme _______ and contribute to _______________________

Back 93

PDL, alveolar bone formation

Front 94

tooth germs that give rise to the __________________, _______________, ______________ form due to further proliferative activity within the _____________ (epithelial) at its deepest extremity, growing deep into the surrounding connective tissue.

Back 94

permanent incisors, canines, premolars

dental lamina

Front 95

for succedaneous teeth, another tooth bud is formed on the ________ aspect of the deciduous tooth germ which remains dormant for some time.

Back 95

lingual

Front 96

____________, which are non-succedaneous teeth, arise from the ____________ of the maxillary and mandibular dental laminae.

Back 96

permanent molars, posterior extensions

Front 97

the formation of the posteriorly directed extension of the original dental laminae begins in the ____ month of gestation.

Back 97

5th

Front 98

cells of the VESTIBULAR LAMINA degenerate to form a cleft that become what 5 things?

Back 98

vestibule of the mouth, internal lining of the lips, cheeks, alveolar mucosa, and gingiva

Front 99

some of the vestibular lamina forms minor _______ and ______ salivary glands.

Back 99

labial, buccal

Front 100

what is the enamel knot?

Back 100

embryonic signaling center providing provisional information for tooth morphogenesis.

Front 101

what cells induce the cells of the enamel knot to begin express signaling molecules?

Back 101

ectomesenchymal cells of the dental papilla

Front 102

what cells control the folding of the inner enamel epithelium?

Back 102

cells of the enamel knot

Front 103

each tooth germ has a single primary enamel know at the _____ stage, and as these disappear, secondary enamel knots appear at the tips of the future cusps in molars.

Back 103

cap

Front 104

the enamel knot undergoes _________, a mechanism to terminate the signaling functions of this structure

Back 104

apoptosis

Front 105

where is the enamel knot located?

Back 105

within the enamel organ next to the dental papilla during the cap stage

Front 106

does the enamel knot have a role in crown pattern formation?

Back 106

yes

Front 107

cells of the enamel know require the presence of which 2 growth factors?

Back 107

epidermal growth factor (EGF) and fibroblast growth factor 4 (FGF-4)

Front 108

name the following developmental abnormality:

tooth within a tooth, the enamel organ expands more than it should and invaginates into the dental papilla

Back 108

dens in dente

Front 109

in the fusion abnormality, the fused teeth have an extra wide crown and ______ pulp cavity.

Back 109

one

Front 110

name the following abnormality:

due to one tooth germ attempting to divide into two, resulting in two crowns that are incompletely formed.

incomplete twining of one tooth,

correct number of teeth.

Back 110

germination

Front 111

what is the main thing that happens during the bell stage?

Back 111

histodifferentiation of the enamel organ

Front 112

during bell stage, the peripheral epithelial cells are differentiating into ______ and _________

Back 112

IEE and OEE

Front 113

during the bell stage, what is the center of the enamel organ called and what causes the star shapes?

Back 113

stellate reticulum. star shape caused by desmosomal contacts being forced apart

Front 114

during the bell stage, some epithelial cells between the IEE and SR differentiate into a layer of flattened cells called the _________________ with _____ junctions.

Back 114

stellate intermedium, gap

Front 115

the cells in the SI have ______________ activity to transport phosphate from blood vessels near the SI into the enamel organ.

Back 115

high alkaline phosphate

Front 116

which cells differentiate into ameloblasts to secrete enamel?

Back 116

IEE

Front 117

where is the site where the Hertwig's epithelial rooth sheath (HERS) initiates root formation?

Back 117

cervical loop

Front 118

what is the folding of the IEE due to?

Back 118

intrinsic growth caused by differential rates of mitotic division within the IEE. (not from growth pressues within the dental papilla)

Front 119

what are epithelial pearls/rests of serres?

Back 119

discrete clusters of epithelial cells surrounded by connective tissue formed by the fragmentation of the dental lamina

Front 120

what stage determines crown morphology?

Back 120

bud to cap stage

Front 121

what 4 things does the dental sac (follicle) become?

Back 121

cementum, PDL, connective tissue of the gingiva, alveolus

Front 122

cells of the IEE differentiate into _____________ which mature into _________________

Back 122

preameloblasts, ameloblasts (enamel)

Front 123

all tooth structures are derived from cells of neural crest origin except _________.

Back 123

enamel

Front 124

in the absence of epithelial cells, does dentin develop?

Back 124

NO

Front 125

preodontoblasts and preameloblasts are separated by a membrane called?

Back 125

membrana performative

Front 126

how much enamel is deposited a day?

Back 126

~4 microns

Front 127

what kind of distal junctions do ruffle-ended ameloblasts have?

Back 127

tight distal junctions

Front 128

what do ruffle ended ameloblasts do?

Back 128

transport calcium, phosphate, and bicarbonate ions into the enamel matrix

Front 129

what do smooth ended ameloblasts do?

Back 129

remove enamel matrix proteins and water from enamel matrix

Front 130

what four things make up the REE?

Back 130

postameloblasts, OEE, SI, SR

Front 131

what does the cervical part of the REE form during tooth eruption?

Back 131

junctional epithelium

Front 132

what do preameloblasts secrete to protect the newly formed enamel?

Back 132

acellular noncalcified primary enamel cuticle

Front 133

what do nonamelogenins do?

Back 133

promote and guide the formation of enamel

Front 134

which non-amelogenin protein is the most abundant and what do they do?

Back 134

ameloblastin - controlling the elongation of enamel crystals

Front 135

what does enamelin affect?

Back 135

formation and growth of crytstallities in developing enamel

Front 136

what is tuftelin?

Back 136

a nucleator for hydroxyapatite crystal formation

Front 137

what are adjacent odontoblasts connected via?

Back 137

gap and tight junctions and desmosomes