The Normal Periodontium
The alveolar process
Dr. Abdirahman Hussein Ibrahim
The alveolar process
It is the portion of maxillae and mandible that
forms and support the tooth socket.
It forms when the tooth erupt to provide the
osseous attachment to the forming PDL and it
disappears gradually when tooth is lost
Alveolar process consists of the following
1. External plates of cortical bone consists of
• Haversian bone and
• Compact bone
2. Inner socket wall which is thin compact bone that
appear in radiograph as lamina dura
Histologically it consist of series of opening.
(cribriform plate) through which the neurovascular
bundle link the PDL with the central component of
the alveolar bone
3. Cancellous trabeullae
• found between the two compact layer acts as
supporting alveolar bone.
Interdental septum consist of cancellus supporting
bone enclosed between the compact border.
In addition to alveolar process the jaw bone
consists of basal bone which is located apically
and is not related to tooth.
Facial and lingual portion of socket are formed by
compact bone only.
Cancellus bone surround lamina dura in apical,
apicolingual and inter-radicular area
Content :
Cells:
1. Osteoblast
Osteoblast is the cells that produce the organic
matrix of bone
Organic matrix produced by osteoblast is of
– 90% collagen and
– 10% non collagen protein
The non collagen protein are
• Bone morphogenic protein,
• Osteocalcin,
• Osteonectin,
• Sialoprotein and
• Phosphoprotein
Osteoblast decrease in number by age
2. Osteocytes:
– are cells enclosed in space called lacunae
– Osteocytes are responsible for production of
inorganic matrix
3.Osteoclasts:
– Are multi nucleated cells derived from hemopoietic
tissues
– Responsible for bone resorption
– Containing hydrolytic enzymes that digest the
organic portion of bone
Bone remodeling:
Is the major pathway of bone changes in shape,
resistance to forces, wound repair and calcium
phosphate homeostasis of body
Fundamental principles of bone remodeling is
formation and resorption by osteoblast and
osteoclast.
Regulation of bone remodeling is complex process
controlled by
• Local and
• Hormonal factor such as PTH
bone consist of 99% of calcium when calcium level
in blood decreases receptors on chief cells of
parathyroid gland are stimulated and lead to release
of PTH
Osteoid is the newly deposited bone, it is non
mineralized
Bone mineralization is from advanced means start
form below old osteoid mineralized first
The interdependency of osteoblast and osteoclast
in bone remodeling is called coupling process
Bone resorption is complex process
morphologically related to appearance of the
eroded bone surface (Howships lacunae) and the
large multinucleated osteoclast.
Other mechanism of bone resorption is by creation
of acidic environment which take place by
1. Proton pump
2. Local pressure
3. Bone tumor
This mechanism occur in four steps
1. Attachment of osteoclast to mineralized bone surface
2. Creation of acidic environment by proton pump which
demineralize bone and expose the organic matrix
3. Degradation of organic matrix of bone to its constituents
amino acids by acid phosphatase enzyme
4. Sequestration of mineral ions and amino acid within
osteoclast
Socket wall
• Consist of
Dense lamellar bone
Bundle bone which is the bone
– adjacent to PDL
– Contain great number of sharpey's fibers
– Localized within alveolar bone proper
– consist of thin lamellae parallel to root surface
The cancellous portion of the alveolar bone consists of
trabeculae that enclose irregularly shaped marrow spaces
lined with a layer of thin, flattened endosteal cells.
Cancellous bone is found predominantly in the
interradicular and interdental spaces and in limited
amounts facially or lingually, except in the palate.
More cancellous bone exists in the maxilla than in the
mandible.
Bone marrow
In new born it is red occupying all cavities of the
bone through out life
It under goes changes , it become fatty yellow
In adult bone of jaw it fatty yellow in all cavities
except in tubrosity of maxillary and mandibular
molar areas and ramus of the mandible it is red
marrow
Periosteum
It is tissue covering outer surface of bone
Consist of two layers
Inner layer is lined with osteoblast and osteogenic cell
which can differentiate into osteoblast
Outer layer is of nerve, blood vessels and collagen
fibers.
Endosteium
– Is tissue lining the internal cavities of bone
consisting of single layer of osteoblast in inner
surface while outer surface is fibrous
Interdental septum :
Consist of cancellus bone
Bordered by the socket wall cribriform plates
(lamina dura or alveolar bone proper) of
approximating teeth and the facial and lingual
cortical plates
Distance from the alveolar crest and CEJ
increase with age
It is of 1.8mm and may increase to 2.8 in old
ages
Abnormalities of alveolar bone includes
Fenestration:
– Denuded root surface from bone only covered by
periosteum with intact bone margin
Dehiscence:
– Denuded root surface from bone extend to margin
Dehiscence on the canine and fenestration of the first
premolar.
These abnormalities are more in anterior than
Posterior and on facial surface than lingual one
Causes:
Prominent root contour
Malaligned tooth in thin bony plate
