1. Periodontium (cont.) Bone and alveolar bone Dr Jamal Naim
PhD in Orthodontics
Bone and alveolar bone

3. Functions of bone Support and protect the skeletal functions.
Bone stores minerals, especially calcium and phosphorous, which are mobilized according to the body needs.
Bone protects the internal organs.
Bone marrow manufactures the blood elements.
Bone remodeling is responsible for the development, growth, movements, fracture and repair.

4. Structural Constituents

5. Osteoprogenitor cell
Location: Present in the deepest layer of periosteum and lining the vascular canals of compact bone. Origin: It is mesenchymal in origin. Function: According to the function needed they divide by mitosis to give any type of bone cells Morphology: It resembles mesenchymal cell with pale stained nucleus and little esinophilic cytoplasm.

6. Osteoprogenitor cell

7. Bone cells
All types of bone cells are from the same type, the alters there appearance according to there function: this is what is called cell modulation.

8. Intercellular substance

9. Types of bone
Compact bone
Spongy bone

10. Lamellar bone Compact bone (ivory bone):
It forms the main part of the shafts of the long bone and covers the cancellous bone e.g. ribs and flat bones of the skull.
Its lamellae are arranged in 3 patterns:
Circumferential lamellae
Havarsian lamellae
Interstitial lamellae

11. Compact bone

12. Lamellar bone Circumferential lamellae:
outer circumferential lamellae beneath the periosteum.
inner circumferential lamellae adjacent to the endostium

13. Lamellar bone Havarsian lamellae:
It is the unite structure of the compact bone and is called the Haversian system or osteon.
The Haversian system if formed of Haversian canal which is surrounded by (4-20) concentrically arranged lamellae.
The Haversian canal contains B.Vs., nerves, C.T. and lined by osteoprogenitor cells.

14. Lamellar bone
Osteocytes are arranged concentrically in the osteons (they anastomose with each others by their process).
Haversian canals connected to each others or to the outer surface or to the bone marrow spaces with Volkmann's canal.

15. Lamellar bone Interstitial lamellae:
The Haversian systems are separated from each others by the interstitial lamellae.
They represent the remnants of an old resorbed and remodeled bone.

16. Compact bone

17. Haversian system

18. Bone Trabeculae
Bone Marrow Spaces

19. Spongy bone It is present in the central part of the flat bone.
It is formed of connected bone trabeculae in the form of network to give maximum rigidity.
In between the bone trabeculae, there are bone marrow spaces
The bone trabeculae have osteocytes.

21. Woven bone This type of bone is characterized by:
Irregular arrangement of the collagen fibers.
Great number, large size and irregular arrangement of the osteocytes.
Increase in the organic substance and decrease in the inorganic contents so; it appears radiolucent in X-ray.
This type of bone is resorbed completely and is replaced by lamellar bone.

22. 3. Bundle Bone
It is referred to the bundles of principal fibers of either the periosteum or PDL continue into the bone as sharpeys fibers.

23. Bundle bone
It is found adjacent to the periosteum and periodontal ligament (areas of tension).
It is characterized by the presence of the Sharpey's fibers.
It has less number of cells than Woven bone; but more calcium salts than lamellar bone. So it appears more radio-opaque and called lamina dura.
Its fibers are arranged parallel to the socket wall.

24. Alveolar bone
In X-ray the cribriform plate is referred to lamina dura.

25. Alveolar bone
The alveolar process is that bone containing the alveoli.
It consists of:
an outer (lingual and buccal) cortical plate (compact bone)
A central spongiosa (spongous bone) and
Alveolar bone (bone lining the alveolus), (bundle bone)
The alveolar bone and the cortical plate meet at the alveolar crest (1.5 to 2 mm below the level of CEJ).

26. Alveolar bone

27. Alveolar bone

28. Alveolar bone divided into the: alveolar bone proper
lining of the tooth socket or alveolus
bone is also called the cribriform plate because of the many holes through which Volkmann’s canals pass (from the alveolar bone into the PDL)

29. Alveolar bone
also called bundle bone because Sharpey’s fibers insert into this bone (Sharpey’s fibers = portion of the fibers of the PDL)
these fibers are inserted at a 90 angle into the ABP – but are fewer in number than those found at the cemental surface
consists of plates of compact bone that surround the tooth

30. Alveolar bone varies in thickness from 0.1 to 0.5mm
can see a portion of the ABP on radiographs lamina dura
most cervical rim = alveolar crest – slightly apical to the CEJ in healthy patients

31. Alveolar bone b. supporting alveolar bone
has the same components as ABP
but is considered to be cortical and trabecular bone – different arrangement of bony plates
cortical bone is made up of cortical plates of compact bone found on the facial and lingual surfaces
plates are usually 1.5 to 3mm thick over the posterior teeth and can vary over the anterior teeth

32. Alveolar bone
trabecular bone is located between the ABP and the plates of the cortical bone (cross section of mandible)

33. Alveolar bone alveolar bone can be resorbed with age (edentulous)
the underlying basal bone is less affected with age – because it does not need the presence of teeth to remain viable
loss of teeth + alveolar bone can results in loss in the vertical dimension of the face – “Popeye” facial appearance

34. Alveolar bone
after tooth extraction the clot is replaced with immature bone
later remodelled as mature secondary bone, very similar process to fracture repair in skeletal bone

36. alveolar crest
Cortical plate
alveolar bone

38. Alveolar bone
The alveolar bone is perforated by many foramina to allow blood and nerve supply to the teeth, so it is referred to cribriform plate
Hirschfeld
canal

39. Alveolar bone
Collagen fibers

40. Alveolar bone
Outer compact bone
Spongiosa
Collagen fibers

41. Alveolar bone
Cementum
Spongiosa
Dentin
PDL