Presented by:

Dr.Ayesha Taha

JR I

Department of Pedodontics

and Preventive Dentistry

SPPGIDMS, Lucknow

CONTENT

•Introduction

•Bone-

•Classification

•Bone Histology

•Composition

•Definition of Alveolar bone

•Development of Alveolar bone

•Parts of Alveolar bone

•Interdental Septa

•Alveolar crest

•Thickness of Alveolar bone

•Periosteum

•Endosteum

•Functions of Alveolar bone

•Remodeling and Repair

•Blood supply

•Nerve supply

•Age Changes

•Clinical Considerations

•Conclusion

•References

INTRODUCTION

BONE is a specialized connective tissue that is mainly

characterized by its mineralized organic matrix.

The alveolar process is the portion of maxilla and

mandible that forms and support the tooth socket.

It forms when tooth erupts to provide the osseous

attachment to the forming periodontal ligament; it

disappears gradually after the tooth is lost.

These are tooth dependent bony structures therefore

the size, shape, location and function of the teeth

determines their morphology.

CLASSIFICATION OF BONE

BASED ON DEVELOPMENT

•Endochondral bone

•Intramembranous bone

•Sutural bone

BASED ON THEIR MICROSCOPIC STRUCTURE

IMMATURE BONE OR WOVEN BONE

&

MATURE BONE

•Compact (cortical) bone

•Cancellous (spongy) bone

Bone formation is preceded by

formation of cartilage which is

later replaced by bone

(Horton,1990).

Occurs in extremities of all

long bones, in vertebrae, in ribs,

in articular extremities of the

mandible and the base of skull.

Endochondral bone

•Bone develops directly within the soft connective tissue.

•Occurs in Maxilla and Body of mandible, cranial vault and midshaft of long bones.

INTRA MEMBRANOUS / DIRECT BONE FORMATION

•Bone forms along suture margins

•Not seen in relation to alveolar bone.

•Occurs in skull, fibrous joints.

•Helps skull and face to accommodate growing organs like brain.

SUTURAL BONE GROWTH

Immature bone /Fibrous bone :• These have more cells & fibers in them. • These are first formed bone. • In humans they are found only in fetus or in sockets

of alveolar bone, during fracture repair and sutures of the skull.

• Also Known as Woven Bones.

Mature bone /Lamellar bone: The type of bone which are composed of thin plates (lamellae) of bony tissue.

•Compact (cortical) bone

•Cancellous (spongy) bone

COMPACT (CORTICAL) BONE

• Composed of dense and concentrically arranged bony trabeculae or lamella.

• More solid with fewer cavities.

• Found external to spongy bone

• Presence of haversian system.

CANCELLOUS (SPONGY) BONE

•Composed of bone trabeculae or spicules.

•Has a simple and less organized architecture.

•Has a lattice-work pattern with numerous small cavities.

•Found internal to compact bone.

•Has no haversian system.

Bone

Outer compact bone Central medullary cavity (Trabacular / Spongy /

Cancellous bone)

BONE HISTOLOGY

• Bone whether Compact or Trabecular are deposited in layers, or lamellae, each lamella being about 5µm thick.

Three distinct types of layering are recognised :

Circumferential lamellae encloses the entire adult bone, forming its outer and inner perimeters.

Concentric lamellae forms the bulk of compact bone & forms the basic metabolic unit of bone – The Osteon.Interstitial lamellae interspersed between adj. concentric lamellae and fills the spaces between them.

COMPOSITION OF BONE

BONE

Inorganic (67%)

(Hydroxyapatite )

Organic (33%)

Collagen (28%)

Non collagenous

Proteins (5%)

Cells

1.Ostoblasts

2.Osteoclasts

3.Osteocytes

4.Bone lining cells

•Collagen -Type I collagen

•Noncollgenous proteins- sialoproteins,osteocalcin, osteonectin, osteopontin,proteoglycans, growth factors & serum proteins.

Alveolar process is that portion of the maxilla and mandible that forms and supports the tooth sockets

(alveoli).

DEFINITION

Joseph P Fiorellini, David M Kim, Satashi O Ishikawa. The

Tooth Supporting Structures. In: Fermin A. Carranza, editor.

Clinical Periodontology, 10th edition, Noida: Elsevier; 2009.

p.68–92.

DEVELOPMENT OF ALVEOLAR BONE

Near the end of 2nd month of fetal life, mandible and maxilla form a groove that is opened toward the surface of the oral cavity.

As tooth germ starts to develop, bony septa form gradually.

The alveolar process starts developing strictly during tooth eruption.

PARTS OF ALVEOLAR BONE

Inner socket wall of thin

compact bone called alveolar bone proper.

Cancelloustrabaculae between these two compact

layers.

An external plate of

cortical bone

Alveolar process consists of :

The parts of the alveolar bone

1. Alveolar bone proper

2. Supporting alveolar bone

o Cortical plates

o Spongy bone

ALVEOLAR BONE PROPER

•Cribriform plate (anatomic term)•Lamina dura (radiographic term)•Bundle bone (histologic term, coined by Stein and Weinmann, 1925)

•It is that bone in which the principal fibers of the periodontal ligament are anchored. (Sharpey’s fibers).

•This type of bone contains several layers of bone deposited in orientation parallel to the tooth socket wall.

It is characterized by the scarcity of the fibrils in

the intercellular substance.

It contains fewer fibrils than lamellated bone.

Since bundle bone contains more calcium salts per unit

area than other type of bone tissues, they appear as

dense radioopacities in roentgenograms.

SUPPORTING ALVEOLAR BONE

Surrounds the alveolar bone proper and gives

additional support.

It consists of

o Cortical plates

o Spongiosa/ Cancellous

•It consists of compact bone and forms the outer and

inner plates of alveolar processes.

•It is found in mandible & maxilla although cortical bone

is more prominent in mandible.

•It makes upto 80% of the body of the mandible.

CORTICAL BONE

•It is formed by haversian bone and

compacted lamellae.

•Spongy bone (anatomic term)

•Trabecular bone (radiographic term)

•Cancellous bone (histologic term)

Presence of trabeculae enclosing irregular marrow

spaces lined with a layer of thin, flattened endosteal

cells.

Variation in trabeculae pattern depending upon occlusal

forces and genetically.

CANCELLOUS BONE

Matrix consists of irregularly arranged lamellae

separated by incremental and resorption line.

It makes upto 20% of the body of the mandible.

Cancellous bone is metabolically more active, thus

skeletal metabolism is equal between both cortical &

cancellous bone.

INTERDENTAL SEPTA

•The interdental septa are bony partitions that separate

adjacent alveoli.

•Coronally, the inner & outer cortical plates fuse 1mm apical to

the Cemento-enamel junction.

•The mesiodistal angulation of crest of the interdental septum

usually parallels a line drawn between the CEJ of the

approximating teeth.

The mesiodistal and faciolingual dimensions and shape

of the interdental septum are governed by the size and

convexity of the crowns of the two approximating teeth,

as well as by the position of the teeth in the jaw and

their degree of eruption.

ALVEOLAR CREST

•The alveolar crest is normally rounded or beaded.

•However on the buccal aspect of incisor & canine, the

bone margins ends in a fine sharp edge.

•The contour of crestal margin varies with the shape of

root.

•When root surface is flat, the contour is straight or flat.

•When convex, the contour is scalloped.

•When concave, the bone margin arch coronally.

•Scalloping is accenuated when bone is thin & reduced when

thick.

THICKNESS OF ALVEOLAR BONE-MAXILLA

•The alveolar bone is thicker on the palatal aspect than on the buccal.

•The bone plate is thicker on the posterior region than on the anterior region.

THICKNESS OF ALVEOLAR PROCESS IN MANDIBLE

•In the incisor & premolar region, bone plate is thinner on the buccal aspect than on the lingual.

•In the molar region, Alveolar Process is thicker on the buccal than on the lingual.

PERIOSTEUM & ENDOSTEUM

The outer aspect of cortical bone is surrounded by a connective tissue membrane which has two layers.

1. The outer fibrous layer – Periosteum2. The inner cellular layer - Endosteum

PERIOSTEUM

•It consists of dense irregular connective tissue.

•It serves as a reservoir of osteoblasts.

•The periosteum is important during growth, fracture repair and healing around implants.

•Usually at the periosteal surface, bone formation exceeds bone resorption, creating a net increase in outer diameter of bone with age.

PERIOSTEUM

Its functions are :o Medium through which muscles, tendons and ligaments are attached to bone.

o Nutritive function to the bone

o Osteoprogenitor cells – Important role during development and repair after fracture

o Fibrous layer- acts as limiting membrane (exostoses in cases of periosteal tear)

o Formation of tubercles at site of attachment of tendons.

• Rich in blood vessels, nerves.

• Contains collagen fibresand fibroblasts.

Outer layer(fibrous)

• Composed of osteoblastsand osteoprogenitor cells

• Cellular periosteum

Inner layer (osteogenic)

ENDOSTEUM

•The tissue lining the internal bone cavities is called Endosteum.•It is composed of a single layer of osteoblasts and a small amount of connective tissue.

•It consists of:An inner layer which is osteogenic layer

An outer layer which is fibrous layer.

•It consists of loose connective tissue containingosteogenic cells, that physically seperates the bonesurface from marrow within.

FUNCTIONS OF ALVEOLAR BONE

1.Houses -root of teeth.

2. Anchors - root of teeth to Alveoli.

3. Helps to move teeth for better occlusion.

4.Helps to absorb and distribute occlusal forces generated during tooth contact.

5. Supplies vessels to Periodontal ligament.

6. Houses and protects developing permanent teeth, while supporting primary teeth.

7. Organizes eruption of permanent and primary teeth.

8. Acts as a reservoir for ions.

9. Provide attachment to muscles.

REMODELLING & REPAIR OF ALVEOLAR BONE

BONE TURNOVER(REMODELING)

Modelling -The process by which the overall size and shape of bones is established.

Remodeling –•The process by which there is constant resorption of bone occuring on a particular bony surface, followed by a phase of bone formation.

•It is the replacement of old bone by new bone.

•Bone turnover does not stop when adulthood is reached, although its rate slows.

•It usually takes place at the periosteal & endostealsurfaces leading to changes in shape of growing bone.

BONE REMODELLING

During remodeling, termination of boneresorption by osteoclasts and the initiation ofbone formation by osteoblasts occurs through acoupling mechanism.

The coupling process ensures that the amount ofbone removed is similar to the bone laid downduring the subsequent bone formation phase.

In certain diseases and with age, the resorptionexceeds formation.

SEQUENCE OF EVENTS IN BONEREMODELLING

First, the Osteoclasts tunnel into the surface of bonewhich lasts for 3 weeks

In Haversian canals, closest to the surface, osteoclaststravel along a vessel, resorb the haversian lamellae and apart of circumferential lamellae, and form a resorptiontunnel or CUTTING CONE.

After sometime the resorption ceases and osteoclastsare replaced by osteoblasts.

These osteoblasts lay down a new set of haversianlamellae , encircling a vessel upon a reversal line.

The entire area of osteon where active formationoccurs is termed as FILLING CONE.

BLOOD SUPPLY

It receive blood supply from inferior and superior alveolar arteries for mandible and maxilla , respectively and reaches Periodontal ligaments from three sources; apical vessels, penetrating vessels from the alveolar bone and anastomosing vessels from gingiva.

Nerve Supply

Labial aspect of maxillary incisors, canines & premolarsis innervated - superior labial branches from theinfraorbital nerve.

Buccal aspect of maxillary molar regions innervated -branches from the posterior superior alveolar nerve.

Palatal aspect by greater palatine nerve, except forincisor which is innervated by long sphenopalatine nerve.

• Lingual aspect in mandible -lingual nerve

• Labial aspect of mandibular incisors & canines - mental nerve.

• Buccal aspect of the molars -buccal nerve.

• The nerve enters the periodontal ligament through Volkmann's canal of alveolar bone.

AGE CHANGES

• Similar to those occurring in remainder of skeletal system

• Osteoporosis with ageing

• Decreased vascularity

• Reduction in metabolic rate and healing capacity

• Bone resorption may increase or decrease

• More irregular periodontal surface

• Thinning of cortical plates

• Rarification of bone

• Reduction in no. of trabeculae

• Lacunar resorption more prominent

• Susceptibility to fracture

• Thickening of collagen fibers

• Decrease in water content

CLINICAL CONSIDERATIONS

• FENESTRATION

Isolated areas in which the root is denuded of bone and root surface is covered only by periosteum and overlying gingiva is termed as fenestration.

• DEHISCENCE

When denuded areas extend through the marginal

bone , defect is called dehiscence.

FENESTRATION

DEHISCENCE

MANAGEMENT OF FENESTRATION AND DEHISCENCE

Several treatment modalities includes:

• Root planning along with chlorhexidene mouth rinsing,

• Full thickness mucogingival flap with primary closure,

• Pedicle flap surgery,

• Free gingival grafting,

• Guided tissue regeneration and

• Combination of bone grafting and free mucosal graft.

Buttressing bone- adaptive mechanism against occlusal force (thickened cervical portion of alveolar plate)

Buttressing bone

Management: Osteoplasty followed by gingivoplasty.

The bone l o s s i n per i odonta l d i sease occu r s atl o ca l s i te s , bu t i t i s regu l a ted by bothsystem i c and l o ca l fac to r s .

Bone reso rpt i o n i s p robab ly the most c r i t i ca lfac to r i n per i odonta l a t tachment l o s s l ead i ngto eventua l t oo th l o s s .

Safe guard i ng the i n tegr i ty of the per i odonta ll i g ament and the a l veo l a r bone i s one of themost impor tant cha l l e nge fo r the c l i n i c i a n .

CONCLUSION

Joseph P Fiorellini, David M Kim, Satashi O Ishikawa. The Tooth

Supporting Structures. In: Fermin A. Carranza, editor. Clinical

Periodontology, 10th edition, Noida: Elsevier; 2009. p.68–92.

FerminA.Carranza,Newmann,Takei;clinicalperiodontology;10th

edition;68–92.

R.Tencate,AntonioNanci;oralhistology,development,structure&f

unction;6thedition;111–143

Hagel-Bradway S, Dziak R: Regulation of bone cells

metabolism, J Oral Pathol Med 18:344,1989

Junqueria LC, Carneiro J, Kelley RO: Basic Histology, ed6,

Norwalk, Conn, 1989, Appleton & Lange.

REFRENCES