ALVEOLAR BONE IN HEALTH AND DISEASE YOU KNOW ABOUT DISESE SPREAD

1. GOOD MORNING

2. ALVEOLAR BONE IN HEALTH AND
DISEASE

3. CONTENTS
► Introduction
► Classification
► Composition
► Development of the alveolar bone
► Structure of the alveolar bone
► Radiogrphic features
► Cell types in bone
► Matrix components
► Bone formation
► Bone resorption
► Osseous topography
► Bone resorption and formation-coupling
► Implant-bone interface

4. INTRODUCTION
► Bone is a mineralized connective tissue. It is unique in body in that
it exists both as a tissue and as an organ. An example for Organ is
maxilla and mandible. Each of the bony organs that are collectively
called Skeleton, which is primarily composed of a tissue i.e called
bone. Therefore the bony skeleton is constructed from the same
basic building material which is called bone mass.
► The structural organization and composition of bone reflects the
activity of the cells involved in the formation of the organic matrix.

5. ALVEOLAR BONE:
► The part of the maxilla or mandible that supports and protects the teeth is
known as alveolar bone.
► Functions - mineralised supporting tissue
- gives attachment to muscles
- provide a framework for bone marrow
- act as a reservoir for ions (especially calcium).
- most important biological properties of bone is its "plasticity', allows
it to remodel according to the functional demands placed upon it

6. CLASSIFICATION:
► DEVELOPMENTALLY,
 Endochondral bone – where the bone is preceded by a cartilaginous model
which is eventually replaced by bone.
 Intramembranous bone – where the bone forms directly within a vascular
fibrous membrane.
► HISTOLOGICALLY, according to its density, mature bone can be divided
into;
 Compact (cortical) bone
 Cancellous (spongy) bone

7. COMPOSITION:
Inorganic (65%) Organic (35%)
Hydroxyappatite
Collagen (88-89%) Noncollagenous (11-12%)
BONE
Glycoproteins (6.5-10%)
Proteoglycans (0.8%)
Sialoproteins (0.35%)
Lipids (0.4%)

8. DEVELOPMENT
► Alveolar bone is dependent on the presence of teeth for its development
and maintenance.
► At the late bell stage, bony septa and bony bridge start to form, and
separate the individual tooth germs from another, keeping individual tooth
germs in clearly outlined bony compartment.
► At this stage, the dental follicle surrounds each tooth germ, which is
located between a tooth germ and its bony compartment. Even prior to
root formation, the tooth germs within bony compartments show
continued bodily movement in various directions to adjust to the growing
jaws. This movement causes minor remodeling of bony compartment
through bone resorption and deposition of new bone.

9. ► The major changes in the alveolar processes begin to occur with the
development of the roots of teeth and tooth eruption. As the roots of teeth
develop, the alveolar processes increase in height.
► At the same time, some cells in the dental follicle also differentiate into
osteoblasts and form the alveolar bone proper. The formation of the alveolar
bone proper is closely related to the formation of the periodontal ligament
and cementum during root formation and tooth eruption.
► Thus, the size and shape of the individual developing tooth roots determine
the overall structure of the alveolar bone proper. On the other hand, the rest
of bony structures in the alveolar process are achieved by periosteal bone
formation.

10. FIG. 9-5 A developing root shown by a divergent
apex around the dental papilla (arrow), which is
enclosed by an opaque bony crypt.

11. STRUCTURE OF ALVEOLAR BONE
► The maxilla and mandible of the adult human can be subdivided into two
portions:
(a) The alveolar process that involves in housing the roots of erupted teeth
(b) The basal body that does not involve in housing the roots.
► As a result of its functional adaptation, two parts of the alveolar process can
be distinguished.
 Alveolar bone proper
 Supporting alveolar bone
- cortical plate, which consists of compact bone and forms outer and inner
plates of alveolar processes.
- spongy bone, which fills area between these plates and alveolar bone
proper, also known as cancellous bone.

12. Fig. 13.1 Ground longitudinal through the mandible showing the alveolar bone. A =
Inner layer of compact alveolar bone lining the tooth socket wall; B - outer alveolar
plate of compact bone (note the spongy bone lying between the two plates of alveolar
bone); C = arbitrary boundary between the alveolar bone and the body of the jaw.

13. CORTICAL PLATES:
► Thinner in maxilla…
► Thickest in premolar & molar regions of lower jaw especially on buccal
side. In mandidle- dense..
► In maxilla-perforated-blood & lymph vessels pass. Anterior region-
supporting bone is thin, no cancellous bone. Cortical bone is fused with
alveolar bone proper.
SPONGY BONE:
► Type 1: The interdental and interradicular trabeculae are regular and
horizontal in a ladder like arrangement.
► Type 2: Shows irregularly arranged numerous delicate interdental and
interradicular trabeculae

14. Cancellous Bone
Compact Bone

15. CORTICAL BONE SPONGY BONE
About 85% of bone About 15% of bone
Lesser turnover than spongy Higher turnover
Remodel about 3% of its mass each
year
remodel about 25% of its mass each
year
Mechanical/protective role More metabolic function

16. INTERDENTAL SEPTA:
► consists of cancellous bone bordered by the socket wall cribriform plates of
approx. teeth and facial and lingual cortical plates.
► The mesiodistal angulation of the crest of the interdental septum usually
parallels a line drawn between CEJ of the approximating teeth.
► Distance between crest of the alveolar bone and CEJ in young adults is 0.75-
1.49mm (avg.1.08mm). This distance increases with age to an average of
2.81mm.
► The interdental and interradicular septa contain the perforating canals of
Zuckerkandl and Hirschfeld which house interdental or interradicular arteries,
veins, lymph vessels and nerves.

17. Generally the form of the alveolar bone can be predicted on
the basis of 3 general principles:
1) The position, state of eruption, size and shape of the teeth determine
to a great extent the form of the alveolar bone.
2) When subjected to forces within normal physiologic limits bone
undergoes remodeling to form a structure that best resolves the forces
applied.
3)There is a finite thickness below which bone will not survive but will
be resorbed.

18. Fig. 13.2 Mandible with teeth removed to demonstrate
the components of alveolar bone. A = Outer alveolar
plate; B = inner alveolar plate; C = cribriform plate lining
the socket wall; D = interdental septum; E - interradicular
septum.

19. BUNDLE BONE (LAMINA DURA) AND CRIBRIFORM
PLATE:
► Bundle bone is the part of alveolar bone, into which the fiber bundles of the
PDL insert. The ABP appears as an opaque line called LAMINA DURA.
► Embedded within this bone are the extrinsic collagen fiber bundles of PDL.
► Lining of alveolar bone is fairly smooth in youngsters but with age, the socket
lining become rougher.
► It is referred to as cribriform plate because of perforation through which the
blood vessels, lymphatics and nerves of PDL pass.

20. HAVERSIAN SYSTEM
► Bone is deposited in layers, or lamellae, each lamella being about 5ųm thick.
► 4 and 20 concentric lamellae within each Haversian system.
► The longitudinally running Haversian canals are connected by a series of
horizontal ones (interconnecting canals).
► Three distinct types of layering are recognized:
1) Circumferential lamellae enclose the entire adult bone, forming its outer
perimeter.
2) Concentric lamellae make up the bulk of compact bone and form the basic
metabolic unit of bone, the osteon.
3) Interstitial lamellae are interspersed between adjacent concentric
lamellae and fill the spaces between them.

23. Bone Marrow:
In the embryo and newborn, the cavities of all bones are
occupied by red hematopoietic marrow. The red marrow
gradually undergoes a physiologic change to the fatty or
yellow inactive type of marrow.
In the adult, the marrow of the jaw is normally of the latter
type, and red marrow is found only in the ribs, sternum,
vertebrae, skull, and humerus.

24. Periosteum:
The tissue covering the outer surface of bone is termed
periosteum.
The periosteum consists of:
► An inner layer composed of osteoblasts surrounded by
osteoprogenitor cells, which have the potential to
differentiate into osteoblasts,
► An outer layer rich in blood vessels and nerves and
composed of collagen fibers and fibroblasts.

25. Endosteum:
The tissue lining the internal bone cavities is called endosteum.
The endosteum consists of:
► An inner layer is the osteogenic layer and
► An outer is the fibrous layer.

26. RADIOLOGIC FEATURES
Lamina dura:
► Tooth sockets are bounded by a thin radiopaque layer of dense bone called,
lamina dura ("hard layer").
► It is caused by the fact that the x-ray beam passes tangentially through many
times the thickness of the thin bony wall, which results in its observed
attenuation.
Alveolar crest:
► The gingival margin of the alveolar process that extends between the teeth is
apparent on radiographs as a radiopaque line, the alveolar crest.
► The level of this bony crest not more than 1.5 mm from the CEJ of the
adjacent teeth is considered normal.

27. FIG. 9-6 The lamina dura (arrows) appears as a thin opaque layer of
bone around teeth, A, and around a recent extraction socket, B.

28. ► Radiographs can demonstrate only the
position of the crest; determining the
significance of its level is primarily a
clinical problem.
Cancellous bone:
► The cancellous bone (also called trabe.cular
bone, or spon-giosa) lies between the
cortical plates in both jaws.
► It is composed of thin radiopaque plates and
rods (trabec-ulae) surrounding many small
radiolucent pockets of marrow.
FIG. 9-14 The trabecular pattern in the
posterior mandible is quite variable,
generally showing large marrow spaces and
sparse trabeculation, especially interiorly
arrows,).

29. CELL TYPES IN BONE:

30. Osteoblasts
► These are specialized fibroblast -like cells of mesenchymal origin.
► Cuboidal or slightly elongated , uninucleated cells.
► Contain a cytoplasm rich in synthetic and secretory organelles as rough
ER, Golgi apparatus, secretory granules and microtubules
► Secretes- Osteoid
►unmineralized bone matrix
►thickness –5-10  before reaching a level of maturity conducive to
mineralisation.
►consists of type 1 collagen fibres, more or less parellel to bone.
►There is a lag phase of about 10 days before the deeper layer of
osteoid has matured sufficiently to undergo mineralisation

31. Functions of osteoblasts
► Secretion of osteoid and control of mineralization
of bone
► Production of paracrine and autocrine factors
► Production of proteases, which are involved in
matrix degradation

32. Osteoblasts control the process of mineralization at
three levels:
► primary calcification, by production of an extracellular
organelle called the matrix vesicle
► secondary calcification, by modifying the matrix
through the release of different enzymes
► by regulating the amount of ions available for mineral
deposition in the matrix

33. Osteocytes
- ‘Entrapped' osteoblasts’.
- Decreased quantity of secretory organelles
- Smaller size with large nucleus
- Formative and resorptive activity of these cells
may vary under certain metabolic
requirements-”OSTEOCYTIC OSTEOLYSIS”
- Numerous cell processes from the osteocytes run
in the canaliculi in all directions.
- About 25000 osteocytes per cubic millimetre of
bone
- Detect stress induced in bone-regarded as the
mechanoreceptors of bone.

34. Bone lining cells
 cover most but not all quiescent bone surfaces
 decreased protein secretion
 relative paucity of organelles
Quiescent surfaces are known to be a primary site of
mineral ion exchange between blood and adult bone.

35. Fig. 13.8 Horizontal section of bone demonstrating a layer of
osteoblasts (A) lining a surface where active bone formation is
occurring (as indicated by the presence of a pale staining layer of
osteoid), some large multinucleated osteoclasts (B) lying against
Howships lacunae in a region of bone undergoing resorption, and large
numbers of osteocytes (C) lying embedded within the bone matrix itself.
D - Bone-lining cells; E - pale-staining osteoid layer

36. OSTEOPROGENITOR CELLS:
► The cells that eventually give rise to osteoblasts are termed
osteoprogenitor cells.
► Reside in the layer of cells beneath the osteoblast layer in the periosteal
region, in the periodontal ligament, or in the marrow spaces.
► fibroblast-like cells, with an elongated nucleus and few organelles
► life cycle-up to about eight cell divisions

37. Friedenstein (1973) divided osteoprogenitor cells into;
► Determined osteogenic precursor cells are present in bone
marrow, in the endosteum and in the periosteum thet cover the
surfaces of the bone. These cells possess an intrinsic capacity to
proliferate and differentiate into osteoblasts.
► Inducible osteogenic precursor cells represent mesenchymal
cells present in the other organs and tissues (eg; muscles) that may
become bone forming cells when exposed to specific stimuli.

38. Osteoclasts
► They are derived from haemopoietic cells of the monocyte/
macrophage lineage by fusion of mononuclear precursors, giving
rise to multinucleated cells.
► Osteoclasts are the cells responsible for bone resorption
► Howship’s lacunae : bony concavities
► Osteoclasts may be up to 100 um in diameter and have on average
10-20 nuclei.
► The lifespan of osteoclasts is thought to be about 10-14 days.

39. Fig. 13.35 Alveolar bone showing scalloped outline of a reversal line

40. MATRIX COMPONENTS
► The bone matrix is formed from a scaffold of interwoven collagen fibers
within and between which small, uniform, plate-like crystals of
carbonated hydroxyapatite (Ca10[PO4]6[OH]2) are deposited.
► Other proteins, including proteoglycans, acidic glycosylated and non-
glycosylated proteins associate with and regulate the formation of
collagen fibrils and mineral crystals, or provide continuity between
matrix components and between the matrix and cellular components.
► Small amounts of carbohydrate and lipid contribute to the organic
matrix-comprises 1/3 rd of matrix.
► Calcium and phosphate in the form of poorly crystalline, carbonated
apatite, also described as dahllite, predominates the inorganic phase.

41. COLLAGEN
Collagen comprises the major ~80–90% organic component.
► Type I collagen (>95%) is the principal collagen
► Type V (<5%) collagen
► In addition,type I, III ,V and XII collagens are also present.
► The collagen fibrils in bone are stabilized by intermolecular cross-linking
involving lysines and modified lysines that form pyridinium ring
structures (pyridinolines) - high tensile strength
► In rapidly forming (woven) bone that is produced during early
development and in repair sites, the fibers are extensively interwoven,
leaving a substantial volume of inter-fibrillar space that is largely
occupied by mineral crystals and associated acidic proteins.

42. NONCOLLAGENOUS PROTEINS
► Using dissociative extraction procedures, most of the major noncollagenous
proteins from mineralized bone have been isolated and characterized.
► Some of these proteins, typically osteocalcin and bone sialoprotein, are essentially
unique to mineralized tissues, whereas others, such as osteonectin/ SPARC and
osteopontin have a more general distribution.
► These proteins are released from bone by demineralization, reflecting the
predominant association with the mineral phase. Other proteins are present in bone
in specifically modified forms.
► Certain proteins derived from blood and tissue fluids are concentrated in bone
include albumin, α2HS-glycoprotein, immunoglobulins and matrix gla protein.

43. Some Noncollagenous proteins in bone matrix
PROTEIN KNOWN FUNCTION REGULATION OF
PRODUCTION
Osteocalcin Inhibits mineralization, recruit bone cell
precursors.
1,25-(oH)2 D3, PTH,
Glucocorticoids
Osteonectin Facilitate type 1 collagen mineralization,
supress rate of hydroxyapatite crystal growth,
modulate cell attachment and detatchment
Glucocorticoids,
TGF-β, IGF-1
Osteopontin Cell binding activity, osteoclast anchoring &
mineral binding activity.
1,25-(oH)2 D3, PTH,
Glucocorticoids, TGF-β,
retinoic acid
Bone sialoprotein Cell binding activity 1,25-(oH)2 D3,
Glucocorticoids
Bone proteoglycan
(biglycan)
Function unclear Not well charecterized
Bone proteoglycan-2
(decorin)
Bind to collagen fibers, regulate fiber growth,
bind/present growth factors in matrix.
Not well charecterized
Thrombospondin Bind and organize matrix, cell attachment TGF-β
Matrix gla - protein Prevent growth plate mineralization 1,25-(oH)2 D3, retinoic
acid

44. PHYSIOLOGIC REMODELLING OF ALVEOLAR BONE:
► Complete remodeling of the alveolar bone occurs when the primary dentition is
replaced by succedaneous teeth. The alveolar bone associated with the primary
tooth is completely resorbed together with the roots of the tooth while new
alveolar bone is formed to support the newly erupted tooth.
► The ability of the alveolar bone to remodel rapidly also facilitates positional
adaptation of teeth in response to functional forces and in the physiological
drift of teeth that occurs with the development of jaw bones.
► Formation of alveolar bone is a prerequisite for the regeneration of tissues lost
through periodontal disease and for osseointegration of implants used in
restorative dentistry. Bone remodeling involves the co-ordination of activities
of cells from two distinct lineages, the osteoblasts and the osteoclasts, which
form and resorb the mineralized connective tissues of bone, respectively

45. Fig 15-4 Bone remodelling cycle. Pre-osteoclasts are recruited to sites of resorption, induced to differentiate
into active osteoclasts, and form resorption pits. After their period of active resorption, they are replaced by
transient mononuclear cells. Through the process of coupling, pre-osteoblasts are recruited, differentiated
into active matrix secreting cells, and form bone. Some of osteoblasts become entrapped in the matrix and
become osteocytes.

46. CALCIUM HOMEOSTASIS
► Decreased
blood Ca++ PTH Osteoblasts
IL-1, IL-6
LIF
Monocytes migrates
to bone area
Bone resorption
Inhibits PTH Normal blood Ca++ Ca++ ions released

47. BONE FORMATION
► Formation of bone, which appears to be linked with bone resorption to maintain
bone mass, involves the proliferation and differentiation of stromal stem cells
along an osteogenic pathway that leads to the formation of osteoblasts.
► The formation of a collagen substratum appears to trigger the differentiation of
pre-osteoblastic cells into osteoblasts through interactions with the α2β1
receptor.
► Expression of developmentally regulated genes and transcription factors appear
to be the most useful for defining the early stages of osteodifferentiation.
► Many of the developmental genes, including homeobox genes such as hoxa-2,
hoxd-13 and hoxa-13, dlx5, msx-1 and msx-2, are common to various forms of
organogenesis.

49. BONE RESORPTION:
► Resorption of mineralized tissues requires the recruitment of a specialized
cell, the osteoclast, which is produced by the monocyte/macrophage
lineage of hematopoietic cells that are derived from bone marrow.
► Tencate, described the sequence of events in the resorptive
process is as follows:
- Attacment of osteoclats to the mineralized surface of bone.
- Creation of a sealed acidic environment through the action of the
proton pump, which demineralizes bone and exposes the organic
matrix.
- Degradation of exposed organic matrix to its constituent amino acids by
the action of released enzymes, such as acid phosphatase and cathepsin B.
- Sequestering of mineral ions and amino acids within the
osteoclast.

51. BLOOD SUPPLY
► It receives from inferior and superior alveolar arteries
for mandible and maxilla, respectively and reaches PDL
from three sources; apical vessels, penetrating vessels
from the alveolar bone and anastomosing vessels from
gingiva.

52. INTERNAL RECONSTRUCTION OF BONE:
► During the growth of maxilla and the mandible, bone deposited on the outer
surfaces of the cortical plates.
► In the mandible, with its thick, compact cortical plates, bone is deposited in the
shape of basic or circumferential lamellae. When the lamellae reach certain
thickness, they are replaced from inside by haversian bone. This reconstruction is
correlated to the functional and nutritional demands of the bone.
► In the haversian canals, closest to the surface osteoclasts differentiate and resorb the
haversian lamellae and the part of circumferential lamellae.
► The resorbed bone is replaced by proliferating loose connective tissue. This area of
resorption is sometimes called the cutting cone or the resorption tunnel

53. ► After a time the resorption ceases and the new bone is opposed onto the old. The
scalloped outline of houship’s lacunae thet turn their convexity toward the old bone
remains visible as a darkly stained cementing line, a reversal line.
► This is in contrast to those cementing lines that correspond to a rest period in an
otherwise continous process of bone apposition. They are called resting lines.
► Resting and reversal lines are found between layers of bone of varying age.
► During these changes, compact bone may be replaced by spongy bone or spongy bone
may change into compact bone. This type of internal reconstruction of bone can be
observed in physiologic mesial drift or in orthodontic mesial or distal movement of
teeth.

54. Fig. 13.19 Portion of bone showing the scalloped outline
of a reversal line staining positively (red) for acid
phosphatase (arrows)

55. BONE RESORPTION-FORMATION; COUPLING:
► Many of the factors that result in bone resorption are known to have no direct effect on
osteoclasts, but act indirectly through osteoblasts.
► Most of the receptors to bioactive molecules that cause bone resorption are present on
osteoblasts [e.g. receptors to PTH and PTHrP). Indeed, the main receptor found in
osteoclasts is related to calcitonin.
► Reversal lines mark the position where bone activity changes from resorption to
deposition. Such lines are darkly stained and irregular in outline, being composed of a
series of concavities that were once the sites of the resorptive Howship's lacunae.
They may be seen to contain the enzyme acid phosphatase.
► On account of collagen degradation occurring during bone resorption, analysis of its
special cross links retained in urine (pyridinoline fragments) is used clinically as a
marker to indicate rates of bone remodelling.

56. ► There are several mechanisms whereby osteoblasts might
promote bone resorption:
1) By the local release of substances such as cytokines and growth factors (e.g.
macrophage colony-stimulating factor, osteoprotegerin and interleukins),
osteoblasts could stimulate the production of osteoclasts
2) By releasing enzymes (such as MMPs) to degrade the unmineralised osteoid
layer covering forming bone, osteoblasts could help expose mineralised matrix on
which osteoclasts could attach and commence resorption.
3) By bioactive molecules present within bone (e.g. cytokines, BMPs. TC.F-|3) that
could be activated as a result of osteoclastic bone resorption and subsequently
have an effect on remodelling.

57. Osseous Topography
► The bone contour normally conforms to the prominence of
the roots, with intervening vertical depressions that taper
towards the margin.
► The height and thickness of facial and lingual bony plates
are affected by the alignment of the teeth, by the
angulation of the root to bone, and by occlusal forces.

58. THE IMPLANT - BONE INTERFACE
► The relationship between endosseous implants and bone consistas of one of the
two mechanism:
1) Osseointegration: when the bone is in intimate but not not ultrastructural
cntact with implant or,
2) Fibrosseous integration, in which soft tissues such as fibers and/or cells, are
interposed between the two surfaces.
► Osseointegration concept proposed by Branemark et al
► called functional ankylosis by Schroeder states that there is an absence of
connective tissue or any non-bony tissue in the interface between the implant and
the bone

60. ► After implant insertion; First, woven
bone is quickly formed in the gap
between the implant and bone.
► Second, after several months, this is
progressively replaced by lamellar
bone under the load stimulation.
► Third, a steady state is reached after
about 1 ½ years. Often for oral
implants, occlusal load is allowed as
soon as 2-3 months, while mostly
woven bone is present.

61. ► Bone has a limited elasticity, with an
elasticity modulus of about;
- 10 GPa/m2 for the cortex and
- 1-5 GPa/m2 for cancellous bone.
► If an implant that is 4mm diameter and
10mm long, the minimal width of the jaw
bone needs to be 6-7mm, and the minimal
height should be 10mm (12mm for posterior
mandible- for safety of mandibular nerve)
► This dimension is desired to maintain at
least 1.0 to 1.5mm of bone around all
surfaces of the implant after preparation and
placement.

62. CONCLUSION
► Alveolar bone, which has interdependence with the dentition, has a
specialized function in the support of the teeth. While there are
architectural specifications for alveolar bone that relate to its
functional role, the basic cellular and matrix components are
consistent with oyher bone tissues. Similarly the cellular activities
involved in the formation and remodelling of the alveolar bone and
the factors that infulencethese cellular processes are common to bone
tissues generally. However, specific features, such as the rate of
remodelling, may be unique to alveolar bone and may be important
for its adaptability.

63. REFERENCES:
1) Clinical periodontology; Newman, Takei, Carranza; 9th edn
2) Clinical periodontology; Newman, Takei, Klokkevold, Carranza; 10th
edn
3) Oral anatomy, histology and embryology; Berkovitz, Holland,
Moxham; 3rd edn
4) Tencate’s Oral histology- development, structure and function; Antonio
Nanci; 6th edn
5) Orban’s Oral histology and embryology; S.N.Bhaskar; 10th edn
6) Clinical periodontology and implant dentistry; Jan Lindhe; 4th edn
7) Oral radiology-principles and interpretation; Stuart C. White; 5th edn
8) Periodontics; Grant; 6th edn
9) Jaro sodek&marc D.mckee; Molecular and cellular biology of alveolar
bone; Periodontology 2000, Vol. 24, 2000, 99–126
10) Moon-il cho & Philias r. garant; Development and general structure of
the periodontium; Periodontology 2000, Vol. 24, 2000, 9–27.

64. Thank you…