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48 Cards in this Set

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1st-6th Weeks of Pregnancy
initial development of teeth
3 Phases of Tooth Development
Initiation - Initiates sites for teeth, already have oral cavity (stomodeum)
Morphogenesis - growing of teeth
Histogenesis - add enamel/dentin
@6th Week of Pregnancy
12 mm CRL
Oral Cavity is lined with low columnar cells
Low Columnar Cells
2-3 layers on mesoderm where teeth will develop
1 layer everywhere else
@6th Week of Pregnancy: 1st Primordia
1st recognizable hist. significant differenti. of an organ
1. Primary Epithelial Band
2. Proliferation of these cells across the midline
3. PEB starts to sink into mesodermal tissue
7th-8th Week of Pregnancy
-PEB becomes vestibular band and dental lamina
-tongue & lip are larger
-PEB is buccally situated in maxilla
-Maxillary PEB is wider
Buccal Band of PEB
Becomes Vestibular Band
(lip furrow band)
Marks separation of cheek and gums, thicker process
Lingual Band of PEB
Becomes Dental Lamina
Gives rise to teeth
Grows to be larger than vestibular band
folds into mesoderm
Dental Lamina
@7/8 Weeks - distinguished
small ovoid swellings that involve whole thickness of lamina, ectodermal, are enamel organs of deciduous teeth (dental organs)
Enamel Organs
7th-8th Week, 4 enamel organs in each quadrant, dM2 & M1 grow off distal edge of dM1, 6 dental organs in each quadrant
10th - 11th Week of Development/Pregnancy
40 mm CRL
dM2 Appears
15th-16th Week of development/pregnancy
100mm CRL
M1 Appears
Enamel organs of other permanent teeth appear _____.
AFTER birth
Production of Dental Papilla
Mesoderm massing occurs
Makes up primitive dentin, cementum, pulp chamber, dental follicle
Ectoderm gives rise to
enamel and dental organ
Mesoderm gives rise to
dental papilla (dentin region, pulp, cementum), dental follicle (vascular cocoon that everything is in)
______ triggers the enamel organ.
Dentin
Bud Stage: DentinEnamel Junction
is the fossilized basil membrane /papillary region btw enamel and dentin (where the two were together during formation)
Bell Stage
continuity of meso & ecto @ base
continuity is in the very tip (gubernacular core)
upper region is a guid to the oral cavity, tip will use it as a guide to know where to go
Bell Stage: Dental Lamina
dental lamina grows into the jaws, creates a ledge w/swllings (den organs), @ Bell stage ledge dissolves except for region at tip (guide for emergence), creates isolated tooth germs
Distal side of dM1 has a remant of the gubernacular cord
it is a deteriorated remnant of the dental lamina
Permanent teeth form...
on the lingual side of deciduous developing tooth germ, occurs in 4th Fetal month, 100mm CRL
Enamel Organ has 4 cell types
Innerenamel epitheliam (along inside on DEJ), In that are the Stellate reticulum and stratum intermedium (layer in betw innerenamel cells and stellate), Outerenamel epithelium (outside of DEJ)
Cervical Loop
where all growth takes place in tooth formation, inner and outer epith. cells come together, determining the shape of the tooth
Innerenamel epithelial cells during bell stage
convert into ameloblasts and deposit enamel, when enamel is secreted maybe half the crown is mapped out at the cervical loop, nutrients are taken out of the mesoderm
Enamel & dentin formation begin after
enamel organ takes on cellular differentiation
Fibroblasts
are maintenance cells, main structures in dental follicle to form periodontal ligament
Mesodermal tissue during Bell Stage
dental papilla - capillary appearance and collagen fibers appear, this is in the region where entin will arise
2 Purposes of Dental Follicle
keep tooth in contact w/oral cavity, nurish what is on the inside
Dental follicle is the byproduct of
mesoderm
Dental follicle is the
fibrovascular cocoon hanging from the gubernaculum
the Dental Follicle houses the
tooth germ
5 Key Components
Enamel Organ, inner epith, out epith, stratum/stellate, dental pathway
Inner Enamel Epithelium Functions
-determined the form of the crown
-evokes cells in dental pap to become odontoblasts (then odontoblasts lay dentin, then IEE becomes ameloblasts which cover dentin w/enamel)
-maps the root in conjunction with the outer enamel epithelium
Dentin & Enamel form in Crown
4-6 months in deciduous teeth, mineralization of tooth, continue 8-11 months after birth
Lag btw completion of crown & root growth because
root growth CAUSES emergence
Eruption/emergence
1st movement of completed crown
entails remodeling of surrounding tissue
hole for grubunacular
emergence is not complete until
it meets the antagonists
4 Mechanisms w/tooth Emergence
1. Pulpal Growth
2. Root Formation
3. Periodontal Ligament Formation
4. Bone deposition & resorption
5 Theories for Eruption
1. Root Growth
2. Bone Growth
3. Growth of Pulp
4. Increase in Blood Pressure
5. Periodontal Ligament Form.
Clinical Practice includes
tooth measurements (x-rays)
Histology
#/frequency of cells in mitosis in pulpal region
Experiments with rats and rabbits because
they have continuously growing incisors
When the Sheath of Hertwig breaks down
the exposed dentin triggers a response from dental follicle (undifferentiated mesodermal cells become cementecytes and secrete cementum)
Hertwig has
2 layers and grows the root (coninuation of dentin)
After cementum -->
-pulls in collagen fibers through follicle
-other end of fibers are attached to alveolar bone
-follicle becomes part of the alveolar bone
The crown NEVER
touches the mesoderm because it emerges through ectodermally lined pathway (no bleeding)
3 Things for functional occlusion
1. early tooth development (initiation and morphogenesis) (crown and root development)
2. formation of hard tissues (histogenesis)
3. root formation