Teeth Dental Histo Flashcards
What is the portion of the tooth embedded in bone called?
tooth root
What is the tooth grossly divided into ?
the root and crown
What is the part of the tooth that is in part of the jaw?
alveolar ridge
What is another word for the tooth socket?
alveolus
What is the portion of the tooth that projects into the oral cavity?
crown
What is the composition of enamel?
1% organic material
96-98% hydroxyapatite
What secretes enamel?
tall, columnar ameloblasts of the enamel organ
When do the ameloblasts degenerate?
when tooth erupts
At what point can enamel no longer be replaced by new synthesis?
when the tooth erupts
What is a tome’s process?
apical, secretory end of ameloblast that is a large, single process
What does enamel mineratlization look like?
results in highly calcified enamel rods or prisms
what do enamel rods look like ?
roughly hexagonal, 4-8 um in diameter
What are the enamel rods/prisms separated by?
interprismatic material (less mineralized)
Where do enamel rods extend to and from?
from ameloblasts to the enamel surface to dentino-enamel junction
What is the bulk of the tooth composed of?
dentine
What secretes dentine
odontoblasts of dental papilla
How is dentine secreted?
as non-mineralized pre-dentine
What is the composition of dentine?
70-80% hydroxyapatite
Type I collagen
GAGs
What do the matrix vaculoes in dentine carry and what is their function?
Calcium and PO4-
- plays a key roles in mineralization of dentine matrix
How is dentine arranged?
dentine tubules (hollow parallel tubes radiating from pulp cavity)
What does the central pulp cavity contain?
-sensory nerves and blood vessels
What innervated dentine?
myelinated nerves
What embryonic layer is dental pulp from?
mesoderm
What does the tooth root contain?
- stellate fibroblasts
- reticular fibers
- collagen
- ground substance
What is the tooth root covered by?
thin layer of cementum
What is cementum composed of?
45-50% hydroxyapatite
What makes cementum?
cementoblasts that mature to cementocytes
How do cementocytes makes more cementum?
one that lie against the surface of the periodontal ligament make via appositional growth
What is the region of tooth between the root and crown?
neck
What protects the neck of the tooth?
gingiva
What does attached gingiva cover?
upper alveolar bone
What does free gingiva cover?
forms cuff around neck of the tooth
What is the space between the free gingiva and the crown called?
gingival sulcus
What is crevicular epithelium?
lines the gingival sulcus with the thin layer (2-3 cells thick)
What is the name of the tissues that surround and support the tooth?
periodontium
What are the parts of the periodontium?
epithelium, cementum, periodontal ligament & alveolar bone
What anchors the bone of alveolus to the cementum layer?
periodontal ligament
- dense collageous fibers called Sharpey’s fibers
What allows for the slight movement of teeth during mastication?
periodontal ligament
What are the clusters of epithelial cells within periodontal ligament?
vestigial epithelial rests (of Malassez)
What in the tooth is from ectodermal origin?
enamel
What cell layers are teeth made from?
-ameloblasts from enamel organ
-odontoblasts of dental papilla
What in the tooth is from mesodermal origin?
dentine, cementum, pulp, periodontal ligament
When is there first some sign of tooth development?
6 weeks i.u.
-a horseshoe shaped epithelial ridge from the oral epithelium
What is the early bell stage of tooth development?
- create an enamel organ
- loosely arranged stellate cells and peripheral layer of cuboidal/columnar epithelium
- formation of internal enamel epithelium (ameloblasts)
- form dental papillae with odontoblasts
What does the internal enamel epithelium differentiate into?
a layer of ameloblasts and 2-3 layers of stratum intermedium
What does the mesenchyme condense to form during the early bell stage?
dental papillae
What is the layer of cells lining the outer convex surface of the enamel organ of tooth?
external enamel epithelium
What is the layer of cells lining the concave surface on the outside of the enamel organ?
internal enamel epithelium (ameloblasts)
What is amelogenesis?
enamel formation
What is the layer deep to developing enamel?
dental papilla (odontoblasts)
What do cells lining the convex surface of the dental papillae during odontogenesis?
odontoblasts
What is dentinogenesis?
form dentine
Development of ameloblasts induces what?
differntiation of odontoblasts
What do odontobalst proccesses make?
dentine tubules
Calcification of dentine induces what?
depositon of enamel
What is tooth formation initiated by?
deposition of organic pre-dentine by odontoblasts
Calcification of dentine matrx secondarily induces what?
enamel production by ameloblasts
When does the enamel organ and ameloblasts degenerate?
tooth eruption
When dental papilla shrinks what does it become?
dental pulp
What is denta?
papillae enclosed by dentine to become to pulp cavity
What does the Hertwig’s root sheath do?
initiates the formation of dentine in the root
What is a proliferation of epithelial cells located at the cervical loop of the enamel organ?
hertwig’s root sheath
After tooth formation is complete, small amounts of ________ continue to be produced.
2’ dentine
What can 2’ dentine do?
may eventually obliterate the pulp cavity
What does the surrounding mesenchym form around the hertwig sheath?
dental follicle (turns into periodontal ligament)
What determines the cross sectional outline of the tooth?
sheath of Hertwig
What does the surrounding mesenchyme form (enamel organ)?
dental follicle-> periodontal ligament
When does tooth development start?
6th week of fetal development
How many roots do incisor and canines have?
usually one
How many primary teeth?
20
When do permanent teeth replace primary?
6-12 years old
When do teeth erupt (primary)?
6-30 months
What does tetracycline cause in teeth?
yellow discoloration of teeth
What is the human dental formula?
I 2/2, C 1/1, P 2/2, M 3/3
What are some examples of dental disorders?
abnormal tooth eruption
orthodontia
dental caries
periodontal disease
gingivitis
periodontitis
What causes periodontal disease?
accumulation of calcified food & bacterial debris (plaque) in gingival sulcus
- results in widening of gingival sulcus, possible inflammation & destruction of periodontal ligament
Why do dental caries happen?
—results when weak acids in food & drink erode calcified enamel, augmented by bacterial action
What helps to harden the enamel and kill bacteria?
fluoride
What treatment happens when caries extend into dentine/pulp cavity and cause an abscess or death of tooth?
root canal
What causes periodontal disease?
accumulation of calcified food and bacterial debris (plaque) in gingival sulcus
What does periodontal disease cause?
widening of gingival sulcus, possible inflammation and destruction of periodontal ligament
What is the inflammation of gums?
gingivitis
What is the periodontitis?
inflammation of periodontal ligament
How does tooth numbering work?
start on upper R wisdom tooth (1) -> upper L wisdom tooth (16)
lower L wisdom tooth (17) -> lower R wisdom tooth (32)
