ALVEOLAR BONE

BONE COMPOSITION OF BONE CLASSIFICATION OF BONE ALVEOLAR PROCESS DEVELOPMENT STRUCTURE INTERNAL RECONSTRUCTION FUNCTIONS AGE CHANGES

CONTENTS

Bone is a living tissue, which makes up the body skeleton and is one of the hardest structures of the animal body.

It provides shape and support for the body. Bone serves as a storage site for minerals and

provides the medium, the marrow for the development and storage of blood cells

Bone

Composition of bone

Inorganic- hydrox-yapatite crystals

67%

Collagen fibers28%

5%Oteonectin, osteo-calcin, phosphopro-tien, sialoprotien,

BSP

BONE

The bones can be classified on many basis, but their histological classification is of more relevance to us

Classification of bone

bone

mature

Compact or cortical

Cancellous or spongy

immature

Woven bone

Compact bone (cortical bone) consists of tightly packed osteons or

haversian systems forming a solid mass. since the bone mass is arranged in layers, it

is called lamellar bone Cancellous bone (spongy bone) it has a honeycomb appearance, with large

marrow cavities and sheets of trabeculae of bone in the form of bars and plates

Mature bone

Compact bone

1. Haversian

system

(osteon)

2. Haversian

canal

3.Interstitial

lamella

4. osteocytes

Cancellous bone

Woven or immature bone is the first formed bone with irregularly oriented collagen fibers of varying diameters.

usually not seen after birth However, it is seen in alveolar bone and

during healing of fractures.

Immature bone

Woven bone

1.Intercellular

bone matrix

2.Osteocytes

3.Periosteum

4.Osteoclast

mandible

maxilla

Alveolar process

alveolar process is defined as that part of mandible and maxilla that forms and supports the sockets of the teeth

They develop during the eruption of tooth and disappear after the tooth is extracted or lost

Introduction

Development The alveolar bone develops from the dental

follicle. From the 2nd month of fetal life, the maxilla and

mandible form a groove that open towards the surface of oral cavity.

The ectomesenchymal cells of dental follicle differentiate into osteoblasts lay down a matrix called osteoid.

As tooth germs start to develop, bony septa form gradually.

The alveolar process start deveoping strictly during tooth eruption

Bud Stage

dental papilla enamel organ

dental follicle

Developing alveolar process

Developing alveolar process

developing tooth

Meckel’s cartilage

bone of mandible

Structure

Alveolar

bone proper

•Bundle •Lamellar boneSuppor

ting alveolar bone

•Cortical plates•Spongy bone

The alveolar bone consists partly of lamellar bone and partly bundle bone and is about 0.1-0.4 mm thick

bundle bone

cementum

lamellated bone

dentin

haversian system

Bundles of PDL

Alveolar bone proper

The alveolar bone proper which forms the inner wall of socket is perforated and is known as cribriform plate.

interdental septum

Bone between the teeth is called interdental septum and interradicular septum.

interradicular

septum

interdental

septum

The interdental and interradicular canal contain the perforating canals of zuckerkandl and hirschfeld

Interradicular septum

The alveolar bone proper surrounds the root of tooth and gives attachment to principle fibers of PDL

The lamellar bone has many osteons each of which has a blood vessel in a haversian canal.

Bundle bone Bundle bone is that bone in which the principle

fibers of periodontal ligament are anchored. Radiographically it is referred to as lamina dura.

Lamellar bone

lamellated bone

dentin sharpey’s fibers

cementum bundle bone

PDL lamina dura

reversal line

bundle bone

Supporting alveolar bone The supporting alveolar bone consists of two

parts :- cortical plates spongy bone

cortical plates

spongy bone

Alveolar bone proper

PDL

tooth

Cortical plates consist of compact bone and form the outer and inner plates of the alveolar processes.

The cortical plates are thin in maxilla than in mandible.

They are thickest in premolar and molar region of lower jaw

cortical plates

Cortical plates

Spongy bone fills the area between the cortical plates and alveolar bone proper.

spongy bone

It is of 2 main types type 1:- the interdental and inter radicular

trabeculae are regular and horizontal type 2:- shows irregularly arranged,

numerous, delicate interdental and interradicular trabeculae.

Spongy bone

Bone re-modeling is an unique and important process that takes place in the bones.

It involves the bone resorption by the osteoclasts on one hand and the matrix deposition by osteoblasts on the other hand.

Periods of resorption alternate with periods of rest and repair.

Islands of bundle bone are separated from the lamellated bone by reversal lines

Internal reconstruction

Bone remodeling

Houses the roots of teeth

Anchors the roots of teeth to the alveoli

Helps to move the teeth for better occlusion

Helps to absorb and distribute occlusal forces generated during tooth contact

Supplies vessels to PDL

Houses and protects developing permanent teeth while supporting primary teeth

Organizes eruption of primary and permanent teeth

functions

Alveolar bones appear jagged and uneven

The marrow spaces have fatty infiltration

The alveolar process in edentulous jaws decreases in size

Loss of maxillary bone is accompanied by increase in size of maxillary sinus

Internal trabecular arrangement is more open, which indicates bone loss.

The distance between the crest of alveolar bone and CEJ increases with age (2.81 mm approx)

Age changes

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