alveolar bone 2016

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3. Definition:
 Alveolar Bone is a Part Of The Jaw Bone (Mandible Or Maxilla) That Form The
Sockets And Support The Teeth In Their Position.
 All types of bone are composed of outer sheet of compact bone enclosing medullary
cavity.
Functions:
1. Support the root of the tooth.
2. Act as a media for the embedded fibers of periodontal ligament.
Physical Properties :
1. Bone is a Calcified Connective Tissue.
2. Bone is an Elastic Tissue.
3. Bone is a Highly Vascular Tissue.
4. Bone is a Highly Remodeling Tissue.
Chemical composition:
1- Inorganic component 67%.
2- Organic Component 33% → 28% Collagen Type I.
→ 5% Ground Substance.

5. 1- After breakdown of epithelial root sheath, cementoblast cells
differentiated on the newly formed root dentine and begin to
secrete cementum.
2- At the same time, alveolar bone begin to develop.
3- At the same time, fibroblast cells differentiated from
Ectomesenchymal cells of dental sac and begin to form collagen
fibers of PL.
4- one end of collagen fibers become embedded into the alveolar
bone and the other end embedded within the cementum.
5- the embedded part of collagen fibers within both cementum and
bone are termed:
Sharpy’s Fibers.

6. 1-Alveolar Bone Proper :
A- Bundle bone: facing socket.
B-Compact bone.
2- Supporting Alveolar Bone:
A- Cortical plate (compact bone):
a- Outer cortical plate: facing
lip and check.
b- Inner cortical plate: facing
tongue.
B-spongy bone.

7. Alveolar crest
1-Inter-dental septum:
Part of alveolar bone found
between two adjacent teeth.
2-Inter-radicular septum:
Part of alveolar bone found
between roots of tooth.
3-Alveolar crest:
It is the margin of alveolar
bone.
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8. Definition:
Alveolar bone proper is apart of alveolar bone that form the inner thin wall
of the socket facing the root.
Terminology:
● Alveolar bone proper is perforated by numerous opening that transmit
blood vessels and nerves to periodontal ligament.
● for this reason, the alveolar bone is termed Cribriform Plate.
● Crebriform Plate is an outer manifestation of canals run within the
alveolar bone termed:
Zuckerkandl & Hirschfeld canals
Structure:
● Bundle bone facing the periodontal ligament.
● Lamellar bone (compact) beside bundle bone.

9. Cribriform plate Zuckerkandl & Hirschfeld canals
DentinBone PL
Cementum

10. 1-Alveolar Bone Proper :
Composed of two parts of bone:
A- Bundle bone:
● Bundle bone is layer of bone facing the periodontal ligament.
● Composed of highly calcified bone.
● Sharpy’s fibers of PL are inserted within it.
● Contain two types of fibers: 1- Intrinsic fibers.
2- Extrinsic fibers ( from PL).
● Appear more radio-opaque line around the tooth in X-ray
so++++
Bundle bone is termed Lamina Dura .
● Loss of bundle bone leads to loss of tooth.
B-Compact bone (lamellar bone):
● Lamellar bone is a layer of compact bone adjacent to bundle bone.
● The main function is to support the bundle bone.

11. Lamina Dura CRIBRIFORM PLATE

13. Supporting Alveolar Bone
Outer Cortical Plate:
It is a bony plate forming the outer surface of
alveolar bone Facing lip and check.
Inner Cortical Plate:
It is a bony plate forming the inner surface of
alveolar bone Facing the tongue.
Alveolar
Crest
Alveolar Bone
Proper
Spongy Bone (Spongiosa):
It is a bone forming the main bulk of alveolar
bone between the cortical plate and alveolar
bone proper

14. A- Cortical Plate :
Both Outer and inner Cortical Plates are Composed Of Compact Bone.
Compact bone is composed of :
1. Haversian System: as concentric lamellae (8-20 lamella).
2- Interstitial lamellae lie among Haversian lamellae.
3- Outer and inner circumferential lamellae on the bone surface.
4- Periosteum adjacent to oral mucosa.
B- Spongiosa:
- Spongiosa form the main bulk of alveolar bone.
- Spongiosa is composed of bony trabeculae with more bone marrow spaces
and rich blood supply.
- Maxilla contain more spongiosa with rich blood supply than mandible, so
wound healing is better in maxilla.
- Thickness of Spongiosa varies according to the tooth type, Example,
mandibular incisors have no or little Spongiosa.

15. 1- Bundle bone
3- Spongiosa
2- Lamellar bone
Cementum
Periodontal
ligament
Dentine
Alveolar Bone Tooth

16. SPONGY BONE

18. Osteoblast cells
Definition:
Osteoblasts are connective tissue cells responsible for formation of bone.
Origin:
Osteoblast cells of alveolar bone are originates from Ectomesenchymal cells of dental
follicle.
Site:
Osteoblasts are found within the periodontal ligament covering the alveolar bone in a
layer termed periosteum.
Functions:
1. Formation and secretion of collagen fibers of bone.
2. Calcification.

19. LM.:
Shape: branched oval cells
Nucleus: Nucleus is rounded and centrally located.
 Active cells: have open-faced nuclei.
 Rested cells: have close-faced nuclei.
Cytoplasm: Basophilic cytoplasm.
Cytoplasmic processes:
Cytoplasmic processes of osteoblast are in contact with the adjacent
cell.
EM.:
1- Active cells:
RER., Mitochondria, GC, secretory vesicles.
Open faced nucleus.
Active cells more seen in younger tissue.
2- Less active cells:
Cell organelles is reduced.
Less active cells that enclosed within the bone are termed

21. Definition:
Osteoclast is a Multinucleated Gaint Cell That Resorb Bone.
Origin:
Fusion of Blood Monocyte.
Site:
On the Site of Bone Resorption in a Depression Termed Hawships
Lacuna.
Hawships Lacuna result from the Resorbing Action of Osteoclast cells
Osteoclast cells.

23. Functions:
Resorption of Bone Tissue For:
1- Remodeling (Bone Turnover).
2- Eruption of Teeth.
3- Removing Alveolar Bone After Tooth Extraction.
LM.:
• Shape: Large Cells.
• Nucleous: Multinucleated cells (8-20 nuclei).
• Cytoplasm: Acidophilic Cytoplasm ( red).
Osteoclast Cells Contain:
1- Acid Phosphatase Enzyme.
2- Collagenase Enzyme.
3- Protease enzyme.
Electron microscope:
1- little RER.
2- Golgi complex.
3- Numerous mitochondria and Lysosomes.
4- Ruffled border:
 Border Of The Cell Facing The Resorbing Bone Appeared Striated.
 Function of Ruffled border: Increase The Surface Area of the working side.
5- Clear zone: The region of cytoplasm adjacent to the ruffled border are not contain cell
organelles but contain actin and myosin for adhesion of the cell with Hawshyp’s lacuna.
Clear zone Ruffled border

24. A- Bone decalcification:
Removal Of Calcium By The Action Of :
Acid Phosphatase Enzyme (from osteoclast).
B- Organic matrix degradation:
Collagen Breakdown Into Protein Occurred By The Action Of:
Collagenase Enzyme(from osteoclast).
Protein Breakdown Into amino acids by the action of :
Protease Enzyme(from Osteoclast).
C- Clearance:
Clearance of the west products Into Blood Stream By The Action Of:
Blood Monocyte.

25. Area of pressure:
Bone Resorption.
Area of Tension:
Bone Deposition.

26. 1- Resorption occurs to the bundle bone of alveolar bone
proper facing the periodontal ligament.
2- Resorption occurs to the compact bone and become
replaced by new layer of bundle bone.
3- Resorption occurs to the spongiosa facing alveolar bone
proper and become replaced by new layer of compact
bone.
NB: Both Bundle Bone And Lamellar Bone Of Alveolar
Bone Proper Must Be Of Normal Thickness.
NB: Loss Of Bundle Bone Means Loss Of Tooth.

27. 1- Bone Formation Occurs To The Bundle Bone Facing The
Periodontal Ligament Leading To Increased Thickness.
2-Resorption occurs to the bundle bone of alveolar bone
proper facing the lamellar bone and replaced by compact
one.
3- Resorption occurs to the compact bone facing the
spongiosa and replaced by spongy bone.
NB: Both Bundle Bone And Lamellar Bone Of Alveolar Bone
Proper Must Be Of Normal Thickness.
NB: Loss Of Bundle Bone Means Loss Of Tooth.

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