Alveolar bone

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ALVEOLAR BONE

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BONEPart I

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Bone TissueBone tissue

◦is a specialized form of connective tissue and is the main element of the skeletal tissues.

◦is composed of cells and an extracellular matrix in which fibers are embedded.

◦is unlike other connective tissues in that the extracellular matrix becomes calcified.

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Functions of BoneSkeletal function of support,

protection, locomotion and attachment of muscles

Bone constitutes an important reservoir of minerals

Bone is for hemopoiesis

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Composition of Bone65% Inorganic

(Hydroxyapatite)◦ Mostly Calcium and

inorganic orthophosphate deposited between collagen

35% Organic◦ 28% collagen◦ 5%

Osteocalcin Sialoprotein Phosphoprotein Osteonectin Bone specific protein

Composition of bonesInorganic Sub-stances

Organic Sub-stances

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Structural Elements of Bone

Bone Cells◦ Odontoblasts – forms bone◦ Osteocytes – maintains bone◦ Osteoclasts – resorbs bone

Bone Matrix◦ is the intercelluar substance of bone consisting of

collagenous fibers ground substances & inorganic salts

Sharpey’s Fibers◦ Are a matrix of connective tissue consisting of bundles of

collagenous fibers connecting periosteum to bone

Blood vessels, nerves, lymph vessels

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Histological Arrangement of Mature BoneCompact Bone

Spongy Bone

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Compact Boneare dense outer sheet that are

closely packed3 Distinct Layering:

◦Circumferential lamella◦Concentric lamella◦Interstitial lamella

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3 Distinct Layering of Compact Bone:Circumferential Lamellae - enclose

the entire adult bone, forming its outer perimeter

Concentric Lamellae - make up the bulk of compact bone and form the basic metabolic unit of bone, the osteon

Interstitial Lamellae - interspersed between adjacent concentric lamellae and fill the spaces between them

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Spongy BoneAlso called Cancellous boneflattened spicules surrounding

the spaces known as marrow spaces containing the bone marrow

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Osteon - basic metabolic unit of bone generally oriented in the long axis of bone

Haversian Canal - canal lined by a single layer of bone cells at the outer of an osteon; each cana; houses a capillary

Volkman’s Canal - channels that connect adjacent haversian canal; contains blood vessels

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Periosteum – osteogenic connective tissue membrane that surrounds every compact bone; consists of 2 layers

Inner layer – consists of bone cells; their precursors and a rich microvascular supply

Outer layer – more fibrous, gives rise to…

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Bone Formation (Ossification)Endochondral (Intracartilaginous)

Bone Ossification◦Has a precatilaginous stage

Intramembranous Bone Ossification◦Mandible and maxilla

Sutural Bone Growth

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ALVEOLAR SOCKETPart II:

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Alveolar Socket

Also called Dental alveolus

are sockets in the jaws in which the roots of teeth are held in the alveolar process with the periodontal ligament.

http://en.wikipedia.org/wiki/Dental_alveolus

Alveolar socket of the second premolar tooth in a bovine maxillary bone.

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ALVEOLAR PROCESSPart II:

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Alveolar process is the thickened ridge of

bone that contains the tooth sockets on bones that bear teeth.

The alveolar process contains a region of compact bone adjacent to the periodontal ligament called Lamina dura.

Maxilla and Mandible◦ Are the tooth-bearing

bones

http://en.wikipedia.org/wiki/Alveolar_process_of_maxilla

http://en.wikipedia.org/wiki/Lamina_dura

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Lamina Durais this part which is attached to

the cementum of the roots by the periodontal ligament.

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Functions of Alveolar bone

Acts as the anchoring of teeth within the alveoli

Absorption and distribution of occlusal pressures produced by intermittent tooth contacts during chewing, swallowing, speech and parafunctional activities such as grinding and chewing

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Structure of the Alveolar BoneCortical Plate – outermost part

◦Alveolar bone proper or laminaSpongiosa – spongy bone

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Cortical PlateOuter bony plate of varying thickness,

which is the outside wall of the maxilla and mandible, covered with periosteum

Continuous with the lamina cribriformis at the orifice of the alveoli – alveolar crest

Consists of haversian systems (osteons) and interstitial lamellae

Thicker in the mandible than maxillaGenerally greater on the lingual than on

the buccal/facial

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Alveolar Bone Proper or LaminaAn inner, heavily perforated bony

lamellae, forming the alveolar wall

In radiograph, appears as radioopaque line distinct from the adjacent spongiosa – Lamina Dura

Contains osteons like other cortical bone, but is distinguished by the presence of Bundle Bone

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Bundle BoneMultiple layers of bone parallel to

surface of alveolar wall which are penetrated by bundles of Sharpey’s Fibers embedded nearly right angle…

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SpongiosaAre spongy (or

cancellous/trabecullar) bone between the 2 bony plates and between the lamina cribriformis of adjacent teeth or roots

Consists of delicate trabeculae, between which are marrow spaces, filled mostly with fatty marrow

Regions of maxillary tuberosity and the angle of mandible, erythropoietic …

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VASCULAR SUPPLY OF ALVEOLAR PROCESSAlveolar process of the maxilla

◦Anterior and posterior alveolar arteries (branch from the maxilla and infraorbital arteries)

Alveolar process of the mandible◦Inferior alveolar arteries (internal)◦Periosteal branches of submental

and buccal arteries (external)