Oral Biology I Midterm

Front 1

Alveolar Bone

Back 1

~67% Inorganic Mineral; Composed of Hydroxyapatite/ Hydroxylapatite [i.e., HAP]: the classic molecular formula is Ca10(PO4)6(OH)2
~33% Organic Matrix;
~85% Collagen Fiber Components (i.e., ~28% of total) Type I Collagen (~98%)
~15% Ground Substance Components (i.e., ~5% of total), ["noncollagenous" proteins] [i.e., GROUND SUBSTANCE]

Front 2

Circumferential Lamellae

Back 2

form the outer perimeter that encloses the bone (are relatively thin and avascular)

Front 3

Concentric Lamellae

Back 3

form the bulk of the lamellar bone; composed of Osteons, which are the basic metabolic unit of bone (are consequently relatively thick and vascular)

Front 4

Interstitial Lamellae

Back 4

fill in the spaces between adjacent concentric lamellae; actually are residual fragments of pre-existing concentric lamellae that have undergone dynamic remodeling (are consequently of many different shapes & sizes)

Front 5

Periosteum

Back 5

a 2-layered connective tissue membrane surrounding the external surface of compact bone

Front 6

Periosteum Inner Cellular Layer

Back 6

Bone Cells
Bone Cell Precursors
Rich Microvasculature

Front 7

Periosteum Outer Fibrous Layer

Back 7

includes "Sharpey's Fibers"

Front 8

Endosteum

Back 8

a 1-layered structure covering the internal surface of compact bone & all the trabecular bone.
Composed of:
Bone Cells
Bone Cell Precursors
Rich Microvasculature

Front 9

Important General Principles of Osteon

Back 9

Bone is a vascularized tissue.
Mineralization/Homeostasis of bone requires:
-Blood Supply [therefore, bone volume >> cementum volume]
-Bone-forming Cells
-Minerals
Therefore, a capillary is the central feature of each osteon.

Front 10

Structure of Osteon

Back 10

Single central vascular canal (non-mineralized area), oriented parallel to the long axis of the bone
-Called the Haversian Canal
-Lined by endosteum
-Surrounds one capillary

Multiple lateral vascular canals (non-mineralized areas), generally oriented perpendicular to the long axis of the bone
-Called the Volkmann Canals
-Lined by endosteum
-Each surrounds one capillary
-Interconnect adjacent Haversian Canals, resulting in a vascular 3-dimensional network

Multiple concentric bone cell spaces (non-mineralized areas), generally oriented circularly around the central capillary
-Called Lacunae
-Surrounds the bone cell body (i.e., cell soma)
-The bone cell that resides within the lacuna is called the Osteocyte

Multiple concentric bone cell canals (non-mineralized areas), also oriented circularly
-called Canaliculi
-Surround the cell processes of the osteocyte
-Functional Syncytium [Clinical Relevance: orthodontics]

Front 11

Haversian Canal

Back 11

.

Front 12

Volkmann Canal

Back 12

.

Front 13

Lacunae

Back 13

.

Front 14

Canaliculi

Back 14

.

Front 15

Neurovascular Elements of Alveolar Bone

Back 15

Arterial Supply
-Derived from the Superior and Inferior Alveolar Arteries
-Numerous "perforating" lateral arterial branches also pass through cribriform plate to supply the PDL

Nerve Supply
-derived from respective branches of Fifth Cranial Nerve

Front 16

Cementum

Back 16

-Cementum is a mineralized connective tissue (similar to bone)
-Cementum is avascular (dissimilar to bone): Nutritional/Vascular diffusion from PDL, not from any osteons

Front 17

Two primary functions of cementum

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-Attachment/Support [via Acellular Cementum plus the Hyaline Layer]
-Adaptation/Protection (during tooth movement and wearing) [via Cellular Cementum]

Front 18

Composition of Cementum

Back 18

~60% Inorganic Mineral (Composed of Hydroxyapatite/Hydroxylapatite)

~40% Organic Matrix
[~80-90% collagen fiber components (i.e.,~32-36% total);
Type I Collagen (~98%)]
[~10-20% Ground Substance Components (i.e,~4-8% total)]

Front 19

Lines of Retzius

Back 19

Incremental growth lines seen in enamel; are the result of enamel development.

Front 20

Lines of Owen

Back 20

Long-term incremental growth lines seen in dentin. Perhaps comparable to the Lines of Retzius of enamel.

Front 21

Lines of Von Ebner

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Dily incremental growth lines in dentin.

Front 22

Orthodentin

Back 22

Humans have orthodentin (there are many other kinds of dentin).

Front 23

Peritubular Dentin

Back 23

With age the dentinal tubules constrict as new dentin is deposited. The dentin at the periphery of tubules is peritubular dentin.
Peritubular dentin has different characteristics from Intertubular Dentin.
Calcium staining shows high mineral content of peritubular dentin.

Front 24

Secondary Dentin

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After a tooth comes into occlusion, dentin continues to be deposited, but at a slower rate. Dentin formed after occlusion is called Secondary Dentin.

Front 25

Tertiary Dentin

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Trauma results in localized formation of additional dentin within the pulp. This is Tertiary Dentin.
Tertiary dentin formed in response to a carious lesion.

Front 26

Sclerotic Dentin

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Dentin that has become translucent due to calcification of the dentinal tubules as a result of injury or normal aging. Also called transparent dentin.

Front 27

Dead Tracts

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When dentin is damaged, odontoblastic processes die or retract leaving empty dentinal tubules. Areas with empty dentinal tubules are called dead tracts and appear as dark areas in ground sections of tooth.

Front 28

Blind Tracts

Back 28

With time, these dead tracts can become completely filled in mineral. This region is called blind tracts and appears white in sections of ground tooth.

Front 29

von Korff’s Fibers

Back 29

The first collagen secreted is mantle dentin, characterized by very large collagen fibers call von Korff’s Fibers.

Front 30

Amelogenin

Back 30

A protein found in developing tooth enamel, and it belongs to a family of extracellular matrix (ECM) proteins. Developing enamel contains about 30% protein, and 90% of this is amelogenins.
The function of amelogenins is believed to be in organizing enamel rods during tooth development.

Front 31

Enamelin

Back 31

Enamelin, 3-5% of the matrix.
Highly glycosylated.
Is seen near the ameloblasts during secretion.
Also is enzymatically broken down to smaller units.
Function is not known.

Front 32

Ameloblastin

Back 32

Ameloblastin=sheathelin
5-10% of matrix proteins.
Mostly distributed in rod sheath.

Front 33

Enamelysin (MMP20)

Back 33

The protein encoded by this gene degrades amelogenin, the major protein component of dental enamel matrix.