Alveolar bone

Structure of bone • Bone is a specialized form of

connective tissue.• It consists of : Bone matrix

Cells

Periosteum

Endosteum

1. Bone matrix

Inorganic

OrganicWater

60% by weightIn the form of

apatite crystalsCalcium

PhosphorusMagnesiumPotasiumSodium

25% by weight

90% Type I collagen.Ground substance of

glycoproteins and proteoglycans with

small amount of proteins and lipids.

15% by weight

Bones Cells a) Ostoprogenator cells.b) Osteoblasts .c) Osteocytes .d) Osteoclasts .e) Bone lining cells.

Osteoblast • Bone forming cells• Extensive endoplasmic reticulum • Numerous mitochondria and vesicle• Active in collagen and ground substance formation • Produce intercellular substance called osteoid

tissue

Osteoclasts• Large multinucleated cells• Responsible for resorbtion of bone• Found in depressions in the bone called

Howship’s lacunae

Osteocytes• An osteocyte, a star shaped cells is the most

commonly found cell in mature bone •  Osteocytes have an average half life of 25

years, they do not divide• Occupy a space called lacuna• Few organelles• Play role in calcium homeostasis

Osteoprogenitor cells• Mesenchymal fibroblast like cells• Form stem cell population to generate

Osteoblast.

Bone lining cells• Undifferentiated flattened cells• Line the surface of bone when there is no

deposition or resorbtion

Periosteum and endosteum

• Layers of bone forming cells and connective tissue cover the external and internal surface

• Provide nutrition to bone tissue• supply new osteoblasts

Types of bone1. Mature (Lamellar) bone:

Collagen fibers within each lamella are parallel

Osteocytes are evenly distributeda) compact bone

b) Spongy (Cancellous) bone

2. Immature (woven) bone

3. Bundle bone

Compact bone • Denser than cancellous bone.• Thick and solid• Lamellae are organized in the form of concentric

cylinder surrounding a narrow canal • 5-20 lamellae surround each canal

(circumferential lamellae). • The central vascular canal called Haversian

canal• Haversian canals are connected by transversely

running Volkmann’s canals

Haversian system

Spongy bone • Sponge-like found in the

head of a long bone• Has large marrow spaces• Surrounded by thin

trabeculae.

Bone Trabeculae

Bone Marrow Spaces

Woven bone • Bony tissue characteristic

of the embryonic skeleton in which the collagen fibers of the matrix are arranged irregularly in the form of interlacing networks.

• Less ground substance and less calcified

• Healing sockets after teeth extraction

Bundle Bone • Collagen fibers of PDL

(Sharpey’s fibers) are embedded in it

• More calcified• Restricted to alveolar

bone proper

Alveolar boneThe alveolar bone ( process )

• The part of maxilla or mandible which

supports and protect teeth.

• Dependent on the presence of teeth .

Functions • Forms the bony socket to hold the root of tooth

and attach it through the PDL• It gives attachment to muscle• Framework for bone marrow• Reservoir for calcium

Jaw bones

Basal boneAlveolar process

Alveolar bone proper

Supporting alveolar

bone

Cortical plates buccal ,lingual

Spongy bone

Alveolar process

Alveolar process

Alveolar bone proper • Forms the socket inner wall• Gives attachment to periodontal ligament• Perforated by many openings that carry

branches of interalveolar nerves and blood vessels into PDL

• Consists of lamellated and bundle bone

Supporting alveolar bone • Compact bone• Thinner in the maxilla• Thickest in molar and premolar region

Consist of cortical plate lingual plate (inner plate) labial plate (outer plate) supporting spongy bone (Cancellous bone

between cortical plates and alveolar bone proper)