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1. Alveolar bone:
Anatomy, Biology &
Histology
DR. LB KAMAIT
DEPARTMENT OF PERIODONTOLOGY AND
ORAL IMPLANTOLOGY

2. Contents
 Introduction
 Histology of bone
 Components of bone
 Bone resorption
 Bone remodelling
 Factors responsible for bone resorption
 Factors responsible for bone formation
 Development of alveolar bone & Alveolar process
 Clinical implication

3. Introduction
 Alveolar process is defined as the
parts of the maxilla and mandible that
form and support the tooth sockets
 Forms with eruption of tooth to
provide osseous attachment to
forming pdl
 Disappears with loss of tooth

4.  Because the alveolar processes
develop and undergo remodeling
with tooth formation and
eruption,
 they are tooth-dependent bony
structures

5. Gross histology of bone
 Characteristics of all bone
are dense outer sheet of
compact bone and central
medullary cavity
 Medullary cavity filled with
red or yellow bone marrow
 Trabecular/spongy bone
present in extremities of
long bone

7.  PeriosteumThe tissue that
covers the outer surface
of bone
 2layers
I. outer (fibrous) layer rich
in blood vessels and
nerves
o composed of collagen
fibers and fibroblasts
II. inner layer composed of
osteoblasts surrounded by
osteoprogenitor cells

8.  Endosteum: tissue that lines
the internal bone cavities
 The endosteum is
composed of a single layer
of osteoblasts and
sometimes a small amount
of connective tissue

9. Components of bone
Cellular
osteoblast
osteocyte
bone linng cell
osteoclast
Matrix components
Inorganic
components
Organic
components
Collagenous
protein
Non-collagenous
protein

10. Matrix of Bone
Organic 33%
Collagen
type I(90%)
Non-collagenous
bone sialoprotein, osteocalcin
osteonectin, osteopontin,
proteoglycans, growth factors
serum protein
Inorganic
67%
-Calcium and
phosphate, along
with hydroxyl,
carbonate, Citrate
-mineral salts are
in the form of
hydroxyapatite
crystals

11. Cellular components
Osteoblast:
 Plump, cuboidal,
mononuclear cell that
synthesize collagenous
and non collagenous
bone matrix proteins
Origin: Differentiated
from pluripotent follicle
cells

12.  Osteoblast contains high level of alkaline
phosphatase on the outer surface of their
plasma membrane
 Cytoplasm is intensely basophilic
 Abundant and well developed protein synthetic
organelles such as rough endoplasmic reticulum

13.  Osteoblasts also secret number of cytokines, Growth
factors (RANKL, osteoprotegerin (OPG), latent
proteases and growth factors including bone
morphogenetic protein)

14. Regulation of osteoblast activity
 PTH: PTH receptor present in osteoblast only not in
osteoclast
 stimulate bone resorption and maintain Ca+ balance
 PTHrP(PTH related peptite) are produced by osteoblast in
very early stage of their differentiation and decreases with
maturation
 Persistent increased level of PTHrP increase osteoclast
formation by RANKL formation
 PTH and Vitamin D3 enhance bone resorption at
pharmacological ph and support bone formation at low
(physiological) concentration

15. Growth hormone and insulin stimulates bone matrix and mineralization
by stimulation of IGF-1 from liver
BMP migration, proliferation and aggregation of mesenchymal cells &
differentiation in to osteogenic cells
TGF –β, IGF I,II stimulates matrix production by osteoblast (by - - of
matrix metalloproteinase expression and + + of tissue inhibitors of
matrix metalloproteinases)
FGF, PDGF, promote osteogenesis
Glucocorticoids :prolonged usedepletion of osteoprogenic precursor
cells ++ PTH

16. Osteocytes
 As osteoblast form bone, some become entrapped
within the matrix they secrete, these cell become
osteocytes.
 The more rapid the bone formation, the more
osteocytes are present per unit volume
 Embryonic ( woven ) and repair bonemore
osteocyte compared to lamellar bone.

17.  Osteocytic lacunae
 Canaliculi
 Osteocyte maintain contact with
adjacent osteocyte and osteoblast or
bone lining cell with osteocytic
processes

18.  Canaliculi penetrate bone matrix and permit
diffusion of nutrients, gases, waste products
between osteocytes and blood vessels.
 Sense the change in the environment and
send signals that affect the other cells
involved in remodeling
 Failure of this interconnecting system
between osteoblast and osteocytes leads to
sclerosis and death of bone

19.  Osteocytes posses an
ellipsoid cell body with long
axis parallel to surrounding
bone lamellae
 Oval nucleus with narrow
rim of faintly basophilic
cytoplasm
 Few organelles but
sufficient RER & golgi
aparatus

20. Osteoclast
 Lie in Howship’s lacunae
 Large cell ( 40-100 um)
 15 to 20 closely packed nuclei
 More the nuclei the more resorbing capacity
 Shape variable due to motility
 Acid phosphatase containing vesicles & vacuole
 Mitochondria and golgi complex extensive
 RER sparse

21. Formation of osteoclast
 Derived from hematopoitic cells of monocyte- macrophage lineage
 Their proliferation and differentiation requires cell - cell interaction
with osteoblast and stromal cells

22. Regulation of osteoclast activity
Osteoprotegerin: RANKL antogonist
Estarogen: suppresses the production ofbone resorbing cytokines (IL -1, IL-
6)
production of TGF-β by osteoblast apoptosis of osteoclast
Vitamin D3, PTH: stimulate bone resorption by osteoclast
Calcitonin: inhibit osteoclastic activity
Cytokines ( IL-1,6,11) enhances osteoclastogenesis
(IL-4,10,12,13,18) limit osteoclast formation

23. TNF-β differentiation of osteoclast
OCIL( osteoclast inhibitory lectin)
TGF- β, interferon –γ (inhibits proliferation and
differentiation of committed precursors into mature
osteoclasts
Bisphosphonate ( carbon substituted pyrophosphate
compounds) with high affinity for hydroxy apatite and
ability to inhibit osteoclast bone resorption
PGE2: powerful mediator of bone resorption.

24. Osteogenesis/ ossification
 The process of bone formation is
called osteogenesis
 Two type of bone formation
1. Intramembranous ossification
2. Endochondral bone formation

25. Sequence of event in bone resorption (Ten Cate)
Attachment of osteoclast to mineralized surface
Creation of sealed acidic environment through action of
proton pump which dimenarilizes bone and exposes the
organic matrix
Degradation of exposed organic matrix to its constituent
amino acids by action of enzymes such as acid phosphatase
and cathepsin
Sequestering the mineral ions & amino acid with in
osteoclast

26. Factors regulating bone resorption
1. IL-1: powerful and potent bone-resorbing cytokine Mechanism:
o by stimulating the production and release of PGE2
o Direct action of IL-1 , through an 80 kDa receptor
2. IL-6: resorption formation of cells with an osteoclastic phenotype
3. TNF: resorption mediated by IL-1, IL-6 inhibits differentiation of
osteoblast phenoptype

27. 4. Colony-stimulating factors stimulate differentiation
of osteoclast precursors into mature osteoclasts
indirectly through IL-1 & PGE2
5. Prostaglandins and other arachidonic acid
metabolites:
slow-acting, but powerful, mediators of bone
resorption
and affect both active mature osteoclasts as well as
differentiated osteoclast precursors.
6. Androgen & sex steroids: inbibits IL-1

28. Factors regulating bone formation
1. Platelet derived growth factors: platelets, oseoblast, serum,
o stimulates DNA synthesis & cell replication in osteoblasts
o increases collagen synthesis & bone matrix apposition
2 Heparin-binding growth factors:
o members of family of 7 related heparin binding proteins
o well known acidic & basic FGF
Both factors: mitogenic for bone cells and to enhance
collagen and noncollagen protein synthesis

29. 3. Insulin-like growth factors: IGF I & IGF II
liver
o increases preosteoblastic cell replication & have a
stimulatory effect on osteoblastic collagen synthesis
and bone matrix apposition
o also decrease the degradation of collagen.
4. tranforming growth factor β :
o stimulate pre-osteoblastic cell replication,
osteoblastic collagen synthesis bone matrix
apposition and alkaline phosphatase activity

30. 5. Bone morphogenetic proteins:
o induces chondrocyte differentiation & matrix mineralization
o activates osteoblast precursor cells mature osteoblasts
o stimulate collagen production by mature osteoblasts

31. Development of alveolar process
 At the end of 2nd month of fetal life ,the
maxilla as well as mandible forms a
groove that open to surface of oral
cavity
 tooth germs contained in these groove
(alveolar vessels & nerve)
 Gradually bone septa develops between
this germs

32.  Later primitive mandibular
canal is separated from
dental crypts by horizontal
plate of bone
 Alveolar process in strict
sense , develops only
during eruption of the
teeth and diminishes in
height after the loss of
teeth

33. Functions of alveolar bone
 Houses the roots of teeth
 Anchors the roots of teeth to the alveoli, which is
achieved by the insertion of Sharpey’s fibers into the
alveolar bone proper
 Helps to move the teeth for better occlusion
 Absorbs and distribute occlusal forces (tooth contact)
 Supplies vessels to pdl
 Houses & protect developing permanent teeth while
supporting primary teeth
 Organizes eruption of primary and permanent teeth

34. The alveolar process consists
of the following:
 1. An external plate of
cortical bone is formed by
haversian bone and
compacted bone lamellae.

35.  2. The inner socket wall of
thin, compact bone called
the alveolar bone proper
 It is seen as the lamina
dura in radiographs
 Histologically, it contains
a series of openings (i.e.,
the cribriform plate)

36.  3. Cancellous trabeculae
between these two
compact layers act as
supporting alveolar bone
 The interdental septum
consists of cancellous
supporting bone enclosed
within a compact border

37.  Bundle characterized by
thin lamellae arranged
in layers parallel to root
with intervening
apposition line.
 Some area Sharpy’s
fiber ; completely
mineralized
 most area , it contains
uncalcified core within
calcified outer layer

38. Supporting alveolar bone
It is that bone which surrounds
the alveolar bone proper and
support the alveolus.
consists of
1.Cortical plates
2. Spongy bone

39. a. Cortical plate
Buccal and lingual cortex
Compact bone
thinner in in maxilla
Thicker mand. premolar & molar
Buccal thinner
In ant. Region of both jaw , labial cortical
plate and alveolar bone proper fuses—
so no spongy bone in between

40. b. Spongy bone
Fills the space between cortical
plate and alveolar bone proper
consists heavy traveculae and
bone marrow space
types:
type 1: the interdental and interradicular tra
horizontal (ladder like) . Present in Manbibl
beculae are regular &
e
type 2: the interdental and inter radicular trabeculae are numerous &
irregular present in maxilla
Zuckerkandl and hirschfeld (nutrient canals)

41. Bone marrow
 In embryo and new born , the bone carry red
hematopoietic marrow
 Gradually replaced by fatty or yellow inactive marrow
 Red marrow in adult :
o Ribs, Sternum, vertebra and skull
o Maxillary tuberosity, maxillary and mandibular premolar
and molar area, mandibular symphysis, ramus angle

42. Interdental Septum
 The interdental septum
consists of cancellous
bone that is bordered by
o the socket wall cribriform
plates of approximating
teeth
o the facial and lingual
cortical plates (Figure 1-
56).
 If the interdental space is
narrow, the septum may
consist of only the
cribriform plate

43. Shape of alveolar crest
 Alveolar bone proper and
cortical plate meet each
other at 1.5 to 2mm below
the CEJ
 Constant in health
 If neighbouring teeth are
inclined oblique
 Most common: between
premolar & molar

44. Osseous Topography
 The bone contour
normally conforms to the
prominence of the roots,
with intervening vertical
depressions that taper
toward the margin

45.  The height and thickness of
the facial and lingual bony
plates are ffected by the
i. alignment of the teeth
ii. angulation of the root to
the bone
iii. occlusal forces

46. Fenestration and
Dehiscence
 Isolated areas in which the root
is denuded of bone and the root
surface is covered only by
periosteum and overlying
gingiva are termed
fenestrations
 Marginal bone intact
 When the denuded areas extend
through the marginal bone, the
defect is called a dehiscence

47. Clinical implications
Physiologic mesial migration
By age 40, loss of 0.5cm by physiologic
mesial migration
with time & wear, proximal contact flattened
Mesial migration
Loss of arch length

48. Effect of non functioning
tooth
 Loss of bone volume between cortical
plate
 the bone trabeculae are less numerous
and thin
 Alveolus shows pronounedrarefaction

49. Effect of orthodontic forces
Bone resorbs at the site of pressure and apposed on the
side of tension
At the site of tension, osteoblast are activated & deposit
osteoid
At pressure site, increase
cAMP
Proliferation of osteoclast

50. Effect of tooth loss
Labial aspect of alveolar crest is principal site of
resorption
In maxilla , Residual alv. Ridge upward & inward
In mandible, downward and outward
Reasons of bone loss after is
disuse atrophy
decreased blood supply
unfavorable prosthesis pressure

51. Thank you