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A464-Test 3
lecture 18
49
Anatomy
Undergraduate 4
04/01/2011

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Term
teeth
Definition
very resistant calcified tissue that is attached to bone
Term
function of teeth
Definition
mechanical tools used to increase surface area of ingested foods
Term
tooth structure (oustide in)
Definition
crown, root, enamel, dentin, pulp, cementum, periodontal ligament, alveolar bone, gingiva
Term
crown
Definition
outer portion of tooth that extends above the gums
Term
root
Definition
portion of tooth below the gums
Term
neck
Definition
where crown and root meet
Term
enamel
Definition
very hard surface layer of teeth
Term
function of enamel
Definition
provides a resistant surface to prevent wear of tooth
Term
appearance of enamel
Definition
ground sections finely striated material; H&E decalcified very light staining striations
Term
matrix of enamel
Definition
-95% hydroxyapatite
-4.5% H20
-0.5% organic materials: amelogenins enamelins (not collagen)
Term
structure of enamel
Definition
made up of giant elongated rods of hydroxyapatite crystals bounded by interrod enamel matrix that extend the full thickness of layer
Term
ameloblasts
Definition
specialized epithelial cells that secrete enamel
-elongated columnar epithelial cells that line the upper portion of the enamel organ during tooth development
-cells destroyed by the tooth eruption process
-it is possible to wear down the enamel of the tooth
Term
dentin
Definition
calcified material that makes up the bulk of the tooth
Term
function of dentin
Definition
grind food
Term
appearance of dentin
Definition
ground sections darkly striated material; H&E decalcified light striated layer
Term
matrix of dentin
Definition
-70% hydroxyapatite
-25% type I collagen
-5% GAGs and glycoproteins
Term
odontoblasts
Definition
-cells that secrete dentin
-found in interior surface of dentin or outermost region of the pulp
-mesenchyme-derived cell with an elongated shape and has very fine long processes that traverse the dentin
-odontoblasts are present throughout life and continually add dentin to the tooth
Term
pulp
Definition
innermost connective tissue layer of teeth
Term
function of pulp
Definition
provides nutrition to odontoblasts
Term
appearance of pulp
Definition
H&E loose connective tissue
Term
cells of pulp
Definition
-odontoblasts line outermost layer
-fibroblasts synthesize the ECM found in pulp
-contains many capillaries
-nerve fibers responsible for tooth pain
Term
cementum
Definition
hard bone-like layer that covers the dentin of the root
Term
function of cementum
Definition
protect the dentin of the root, site of attatchment of periodontal ligament
Term
appearance of cementum
Definition
H&E decalcified and ground sections is similar to very dense bone
Term
matrix of cementum
Definition
similar to bone
Term
cementoblasts/cementocytes
Definition
specialized cells that secrete cementum. can be found on surface of cementum as well as in lacunae
Term
periodontal ligament
Definition
unique CT that is found between cementum and bone
Term
function of periodontal ligament
Definition
connects tooth to bone, also shock absorber for tooth
Term
appearance of periodontal ligament
Definition
H&E shows an active CT layer with many fibroblasts, small collagen bundles and abundant capillaries
Term
matrix of periodontal ligament
Definition
high turnover rate of Type I collagen, affected by diseases that influence collagen production, such as scurvy
Term
alveolar bone
Definition
bone that lines the tooth socket
-bone remodeling and resorption process is regulated here
-shock absorption by periodontal ligament prevents stresses of chewing food from producing a lot of osteoclast activity.
-ossteoclast activity can be induced in the orthodontic procedures by directing force on a tooth
-this results in movement to tooth through bone
Term
alveolar bone function
Definition
holds teeth and connects with rest of skeleton
Term
appearance of alveolar bone
Definition
bone with many osteocytes
Term
gingiva
Definition
gums, mucous membrane that surrounds teeth
Term
function of gingiva
Definition
covering of the bones of the jaw serves to protect the bone
Term
appearance of gingiva
Definition
stratified squamous epithelia and underlying loose connective tissue.
Term
epithelial attachment to teeth of gingiva
Definition
epithelia linked to enamel by hemidesmosomes. The epithelia is thick over bones but thin in region of the peridontal space
Term
tooth development (4 steps)
Definition
1. initiation
2. invagination stage
3. maturation stage
4. tooth eruption
Term
initiation
Definition
Tooth development begins from a specialized region of oral ectoderm called a placode

Ectomesencyme-resides underneath the placode

Tooth development is driven by a series of signals passed between epithelial structures and the underlying mesenchyme
Term
ectomesenchyme
Definition
resides underneath placode
Term
invagination stage
Definition
Enamel organ- main invagination of ectoderm has two surfaces outer and inner enamel epithelium

Dental papilla- condensation of ectomesenchyme along inner enamel epithelium

Bud of permanent tooth formed by out growth of invaginated epithelia
Term
maturation stage
Definition
initial production of the matrix that will become teeth

Ameleoblasts differentiate from the inner enamel epithelium and begin producing enamel. At this stage enamel is mostly organic matrix.

Ondontoblasts differentiate from dental papilla cells begin producing dentin.
Term
tooth eruption
Definition
The production of dentin pushes the tooth through the enamel organ destroying this tissue.

When permanent teeth erupt the enamel organ directs an ostoeclast-mediated resorption of the root of the overlaying deciduous tooth.

Humans have 20 deciduous teeth and 32 adult teeth. The adult molars are developed from cellular migrations from the terminal permanent tooth bud.
Term
gingivitis
Definition
The glycoprotein components of saliva are deposited on teeth and this provides nutrients for aerobic bacteria to grow. If undisturbed a lawn of bacteria will grow over the base of the tooth.

If plaque is not removed, it continues to accumulate and in the bottom layer produces conditions favorable to the growth of gram negative anaerobic bacteria.

As gram negative bacteria multiply they release lipid metabolites that trigger necrosis in the gingiva surrounding the base of the tooth surrounding cells and this triggers inflammation. The inflamed tissue is called gingivitis

If gingivitis is unchecked, it leads to degradation of the periodontal ligament beneath the gingiva and the opening of a pocket along the root of the tooth. Ultimately this produces conditions where there is bacterial growth in the region between the teeth. and the recruited lymphocytes produce growth factors that recruit and activate osteoclasts, which in turn degrade cementum and the bone of the tooth socket. Ultimately, the compromised periodontal ligament and eroded bone socket lead to tooth loss.
Term
what is plaque
Definition
a bacterial lawn
Term
what type of bacterium is responsible for gingivitis and periodontal disease?
Definition
anaerobic gram negative
Term
what are the functions of the gingiva and periodontal ligament
Definition
gingival: protect bone

periodontal ligament: connects tooth to bone, shock absorption
Term
in gum disease, what triggers inflammation of the gingiva and periodontal ligament?
Definition
lipids on the cell wall of the gram negative bacteria trigger necrosis of cells which leads to inflammation
Term
what can be done to prevent gingivitis?
Definition
brush and floss
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