Tooth Development and Eruption Flashcards

enamel
Terms Definitions
What are the stages of odontogenesis?
Initiation stage
Bud stage
Cap stage
Bell stage
Apposition stage
Maturation stage
When, in development, is the initiation stage?
6th-7th weeks
When, in development, is the bud stage?
8th week
When, in development, is the cap stage?
9-10th week
When, in development, is the bell stage?
11th-12th week
Initial teeth for both primary and permanent dentitions develop in which region of the mouth?
anterior mandibular followed by anterior maxillary
When do the primary and permanent dentitions form (fetal, embryonic, neonatal, etc.)?
primary--embryonic and fetal
permanent--fetal
Name the stage: ectoderm lining stomodeum gives rise to oral epithelium and then to dental lamina, adjacent to deeper mesenchyme and NCC and separated by a basement membrane
Initiation stage
Growth of dental lamina that penetrates growing mesenchyme
bud stage
Enamel organ forms and surrounds mass of dental papilla from the mesenchyme and is surrounded by a mass of mesenchyme called the dental sac. Formation of the tooth germ
cap stage
differentiation of enamel organ with four cell types and the dental papilla into two cell types
bell stage
dental tissues secreted as matrix in successive layers
apposition stage
dental tissues fully mineralize to their mature levels
maturation stage
T/F: The teeth have the longest developmental period of any set of organs in the body
true
T/F: Mesenchymal tissues must influence the ectodermal tissues in order for initiation of odontogenesis to occur
True
at the beginning of odontogenesis, the outer portion of the ectoderm gives rise to what?
oral epithelium
separates oral epithelium and the underlying mesenchyme
basement membrane
main processes involved in initiation stage
induction
main processes involved in bud stage
proliferation
main processes involved in cap stage
proliferation, differentiation, morphogenesis
main processes involved in bell stage
proliferation, differentiation, morphogenesis
main processes involved in apposition stage
induction and proliferation
main processes involved in maturation stage
maturation
Embryological background of enamel
enamel organ (ectoderm)
Embryological background of dentin
dental papilla (NCC)
Embryological background of cementum
dental papilla (NCC)
Embryological background of alveolar bone
mesoderm
type of tissue: enamel
epithelial
type of tissue: dentin
CT
type of tissue: cementum
CT
type of tissue: alveolar bone
CT
Formative cells of enamel
ameloblasts
Formative cells of dentin
odontoblasts
Formative cells of cementum
cementoblasts
Formative cells of alveolar bone
osteoblasts
incremental lines: enamel
Lines of Retzius
incremental lines: dentin
Imbrication lines of Ebner
incremental lines: cementum
Arrest and reversal lines
incremental lines: alveolar bone
Arrest and reversal lines
Mature cells: enamel
none--lost with eruption
Mature cells: dentin
only dentinal tubules with processes
Mature cells: cementum
cementocytes
Mature cells: alveolar bone
osteocysts
resorptive cells: enamel
odontoclasts
resorptive cells: dentin
odontoclasts
resorptive cells: cementum
odontoclasts
resorptive cells: alveolar bone
osteoclasts
mineral (inorganic) level: enamel
96%
mineral (inorganic) level: dentin
70%
mineral (inorganic) level: cementum
65%
mineral (inorganic) level: alveolar bone
60%
Organic and water levels: enamel
Organic: 1%
Water: 3%
Organic and water levels: dentin
Organic: 20%
Water: 10%
Organic and water levels: cementum
Organic: 23%
Water: 12%
Organic and water levels: alveolar bone
Organic: 25%
Water: 15%
Tissue formation possible, for enamel, after eruption?
no
Tissue formation possible, for dentin, after eruption?
yes
Tissue formation possible, for cementum, after eruption?
yes
Tissue formation possible, for alveolar bone, after eruption?
yes
vascularity: enamel
no
vascularity: dentin
no
vascularity: cementum
no
vascularity: alveolar bone
yes
innervation: enamel
no
innervation: dentin
yes
innervation: cementum
no
innervation: alveolar bone
yes
Disturbances in initiation stage?
Anodontia
Supernumarary teeth
Disturbances in bud stage?
macrodontia/microdontia
Disturbances in cap stage?
dens in dente
fusion
gemination
tubercle (extra cusp)
Disturbances in appostition and maturation stages?
enamel pearl
enamel dysplasia
dentinal dysplasia
concresence
odontogenesis stage when anodontia disturbance occurs?
initiation stage
odontogenesis stage when supernumerary teeth disturbance occurs?
initiation stage
odontogenesis stage when macrodontia/microdontia disturbance occurs?
bud stage
odontogenesis stage when dens in dente disturbance occurs?
cap stage
odontogenesis stage when fusion disturbance occurs?
cap stage
odontogenesis stage when gemination disturbance occurs?
cap stage
odontogenesis stage when tubercle disturbance occurs?
cap stage
odontogenesis stage when enamel pearl disturbance occurs?
apposition/maturation stage
odontogenesis stage when enamel dysplasia disturbance occurs?
apposition/maturation stage
odontogenesis stage when dentinal dysplasia disturbance occurs?
apposition and maturation stages
odontogenesis stage when concresence disturbance occurs?
apposition and maturation stages
Heredity can play a role in all tooth development disturbances except which?
fusion (pressure)
tubercle (trauma, pressure, or metabolic disease)
enamel pearl (displaced ameloblasts to root surface
concrescence (trauma or tooth crowding)
supernumerary teeth usually occurs where?
between maxillary central incisors (mesiodens)
4th molars
premolar region (perimolar)
macrodontia/microdontia usually involves which teeth?
permanent maxillary lateral incisors and third molars
tooth most commonly affected by dens in dente?
permanent maxillary lateral incisor
tubercle usually present where?
permanent molars or cingulum of anterior teeth
concrecense more commonly occurs here:
permanent maxillary molars
Stage where cellular differentiation begins in odontogenesis
cap stage
predominant physiological process occurring during cap stage
morphogenesis
define dental papilla
inner mass of condensed mesenchyme under enamel organ in cap stage
In odontogenesis, the basement membrane is the future site of what?
DEJ
dental sac (dental follicle) becomes what mature structures?
periodontium:
cementum, PDL, and alveolar bone
dental papilla becomes what mature structures?
dentin and pulp
initiation of permanent dentition occurs during which stage of odontogenesis of primary teeth (what week)?
cap stage: week 10
Four cells found in enamel organ--(what stage)?
bell stage:
inner enamel epithelium-->ameloblasts
outer enamel epithelium-->protective barrier
stellate reticulum
stratum intermedium
during bell stage, dental papilla differentiates into these layers:
outer cells--> odontoblasts
inner cells-->primordium of pulp
Describe formation of preameloblasts and why this is important
-IEE cells become more columnar
-repolarization--nuclei move as far as possible from basement membrane
-preameloblasts induce outer layer dental papilla cells differentiation into odontoblasts and they themselves turn into ameloblasts
Which matrix begins formation first? enamel matrix or dentin matrix?
dentin matrix--this is why it is usually slightly thicker than enamel
Describe formation of odontoblasts
-signals from preameloblasts
-repolarization--nuclei migrate as far from BM as possible
-secrete predentin (dentin matrix) by BM
Describe formation of ameloblasts, DEJ and enamel matrix
-when in contact with predentin, BM disintegrates
-when preameloblasts contact predentin, they mature to ameloblasts
-Tome's process of ameloblasts start to secrete enamel matrix--DEJ forms
-matrix formation on both sides of DEJ is rythmic
-odontoblasts learve an odonotblastic process contained in a dentinal tubule
Enamel dysplasia
-occurs during appositional and/or maturation stages
-can be systemic or local
-local from trauma or local infection
-systemic from traumatic birth, systemic infcetion, nutritional deficienceis, or dental fluorosis
enamel hypoplasia
reduction of quantity of enamel matrix--pitted and grooves in enamel surface

examples: Hutchinson's incisors and mulberry molars
congenital syphilis causes
hutchinson's incisors and mulberry molars
enamel hypocalcification
reduction in quality of enamel maturation--opaque, yellow/brown teeth
dental fluorosis can cause what?
both enamel hypoplasia and enamel hypocalcification
a certain type of enamel dysplasia with hereditary etiology--very little or no enamel
amelogenesis imperfecta
a certain type of dentin dysplasia with hereditary etiology--poorly formed dentin
dentinogenesis imperfecta
structure responsible for root development
cervical loop
what is the cervical loop
cervical portion of enamel organ--bilayer rim of only IEE and OEE.
When does root development begin?
after crown is completely shaped and tooth starts to erupt
How is Hertwig's root sheath made?
cervical loop grows deeper into surrounding mesenchyme of the dental sac--encloses more of the dental papilla tissue
cervical loop grows deeper into surrounding mesenchyme of the dental sac--encloses more of the dental papilla tissue. What is this structure called?
Hertwig's root sheath
Function of Hertwig's root sheath?
shape root
induce dentin formation in root area
Why does Hertiwig's root sheath include odontoblastic differentiation in the root area but fail to differentiate into enamel-forming ameloblasts?
Because there aren't stellate reticulum and stratum intermedium in this area.
What happens in root formation
-IEE of Hertwig's root sheath induce outer layer of dental lamina to form odontoblasts
-predentin is laid down
-BM and Hertwig's root sheath disintegrate.
What are epithelial rests of Malassez?
epithelial cell remnants from the disintegrate of Hertwig's root sheath--can become cystic
What causes enamel pearls
misplaced ameloblasts that migrate to the root area
Describe the formation of the deninocemental junction (DCJ)
-disintegration of Hertwig's root sheath allows cells of dental sac to contact dentin
-this contact induces these cells to become immature cementoblasts
-cementoblasts undergo cementogenesis--lay down cementum matrix (cementoid)
-cementoblasts become trapped in cementoid--become mature cementocytes
-as cementoid calcifies, it is called cementum
Which cells form the dental pulp?
central cells of the dental papilla
Name the major component of the PDL
collagen fibers
What causes 2 or 3 roots to be formed as opposed to one?
differential growth of Hertwig's root sheath
What causes dilaceration?
distortion of Hertwig's root sheath due to injury or pressure
Where is dilaceration most common?
permanent maxillary lateral incisors and canines, as well as molars
Accessory roots (supernumerary roots) occur mainly where?
mainly iwht permanent third molars
What is passive eruption
occurs with age--gingiva recedes; no actual tooth movement takes place
Describe tooth eruption
-after enamel appostition ceases, ameloblasts place a dental cuticle on the enamel surface
-layers of enamel organ compress into the reduced enamel epithelium (REE)
-REE fuses with oral epithelium
-REE secretes enzymes that create a tunnel in the fused tissue
Describe primary tooth shedding
-osteoclasts absorb bone between primary and permanent tooth
-odontoclasts cause resorption in the primary tooth's root
residue that is formed on newly erupted teeth of both dentitions
Nasmyth's membrane--fused tissue of REE and dental cuticle on enamel surface...picks up stains, but can be removed by polishing
Generally, what is the relationship between erupting permanent teeth and primary teeth? What is the exception?
permanent teeth erupt into oral cavity lingual to roots of primary tooth. exception is permanent maxillary incisors which are more facial
odontogenic cyst that forms from the REE after the crown has formed and matured is called what?
dentigerous cyst or follicular cyst
dentigerous (follicular) cyst most common in what teeth?
third molars
What do you do when a dentigerous (follicular) cyst forms around the crown of a nonerupted impacted tooth?
Remove it
What do you do when a dentigerous (follicular) cyst forms around a developing tooth? "an eruption cyst"
appears as fluctuant, blue, vesicle-like gingival lesion or partially erupted tooth and will disintegrate during eruption
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