GOOD MORNING…GOOD MORNING…

ALVEOLAR BONE

Presented by

DR NAVEEN PARVATHAREDDYI MDS, NARAYANA DENTAL COLLEGE

contents•Bone – introduction, classification, composition, functions , histology & bone cells

• Introduction of AB•Development of AB•Structure of AB•Blood supply & nerve supply of AB•Functions of AB•Age changes of AB•Clinical considerations of AB•Therapeutic considerations of AB•Summary•References

Introduction

BONE – It is a living specialized connective tissue with calcified inter cellular substance, which makes up the body skeleton and is one of the hardest structures of human body.

Based on location

CLASSIFICATION OF BONES

Axial skeleton Appendicular skeleton

80 126+

206

Based on shape

Based on developmental origin Intra-membranous Intracartilagenous / Endochondral

Based on cross section Compact bone

Spongy bone

Based on Matrix arrangement Lamellar bone Woven bone

Woven bone

•Immature(Woven) Bone •Mature (Lamellar )Bone•Collagen fibers oriented in many directions

•Fibers are orderly arranged

•Interfibrillar space is more

•Interfibrillar space is less

•H&E- Matrix shows blue •H&E- Matrix shows Acidophilic

•Deposition & Mineralization rates are fast.

•Deposition & Mineralization rates are slow.

• Bone sialoprotein present

•Osteocalcin present

Based on Maturity

Immature(Woven) Bone Mature (Lamellar )BoneMineral density is lower &water content higher

Low water content

Entirely removed by osteo clasts.

Portion of lamellar matrix resorbed at one time

Matrix vesicles participate in mineralization

Collagen mediated mechanism is involved in calcification

Composition

Non collagenous proteins

osteocalcin

sialoprotein

phosphoprotein

osteonectin

bone specific protein

bone morphogenic protein

functions•Supportive•Anchorage•Protective•Hematopoietic•Storage•Locomotive

Bone histologyPeriosteum: thin ,tough fibrous membrane

Endosteum: thin , delicate connective tissue membrane

Lamellae of bone:• circumferential lamellae: these lamellae are arranged in parallel layers surrounding bone.

• concentric lamellae: these lamellae are arranged in concentric layers.

• Interstitial lamellae: these are present in between osteons.

• TRABECULAE- spongy bone consists of large slender spicules

Osteon/ haversian system: haversian canal and concentric lamellae are together called as osteon.

Haversian canal: the vascular canal present at the centre of concentric lamellae.

Volkmann’s canals: adjacent haversian systems are connected by volkmann’s canals.Contain vascular network

Lacunae:

Osteocytes: osteocytes are present in the lacunae at the junctions of lamellae.

Canaliculi:

Resting lines: this line has more regular appearence which denotes period of rest during formation of bone. Deliniates haversion system

Reversal lines: irregular lines which indicate previous area of bone resorption.

Hemopoietic tissue• Red marrow – young bone Spongy bone of long and flat bones Contain stem cells of fibroblasts and blood cells• Yellow marrow – old bone Seen in epiphysis of long bones Loss of hemopoietic potential Increased accumulation of fat cells

Bone cells Osteogenic cells: 1. Osteoprogenitor cells. 2. Osteoblasts. 3. bone lining cells 4. Osteocytes. Osteoclasts

Osteoprogenitor cellsStructure : these

are angular shaped cells with centrally placed nuclei.

Function: these cells differentiate in to osteoblasts which form bone.

osteoblasts•Derivation•Reservoir •Morphology•functions

Bone lining cells•The osteoblasts that have completed their function and lie on bony surface as bone lining cells

•These cells contain few cell organelles

osteocytes•As the osteoblasts form bone matrix , they get entrapped within the matrix they secrete are called osteocytes

•Number of osteoblasts that become osteocytes , depends on rapidity of bone formation

•Woven bone, repair bone shows more osteocytes

•Osteocytes are 1o times more than osteoblasts

•Half life •Lacunae , canaliculi

osteoclasts• It is a type of bone cell that removes bone tissue by removing mineralized matrix of bone

•Osteoclasts lie in resorption bays

•Multinucleated•Exhibits 2 zones•Acid phosphatase

Alveolar boneAlveolar Bone (Process) is the part of maxilla & mandible that forms & supports the sockets (alveoli) of the teeth•Also known as Processes Alveolaris

•Pars Alveolaris

Development of AB•At the end of 2nd month of iu life, maxilla and mandible forms a groove

•As tooth germs start to develop , bony septa form gradually

•As root develop, alveolar process increases in height

•During rapid growth period, chondroid bone is formed

alv. Process forms with development and eruption of teeth Morphology of Alv. Bone depends on

Size Shape position of teeth

alv bone attains max thickness Alv. bone undergoes atrophy If teeth congenitally missing – Alv. Bone not developed

BoundariesNo distinct boundary

Certain areas Alveolar bone fused with basal bone

Anterior maxillary region

Posterior Mandibular region.

Structure of ABALVEOLAR BONE

ALVEOLAR BONE PROPER

LAMELLATED BONE

BUNDLE BONE

SUPPORTING ALVEOLAR BONE

CORTICAL PLATE

SPONGY BONE

Structure of ABTwo Parts:

Alveolar Bone proper:

Thin lamellated bone that surrounds the root of the tooth

Gives attachment to the PDL Fibres

Supporting alveolar Bone:

Surrounds the alveolar bone Proper

Gives support to the socket

Alveolar bone proper That lines the socket or alveolusForms the inner wallConsists of two parts0.1 – 0.4 mm thickOtherwise called as cribriform plate

Cribriform plate

Anatomical name

Resembles a fine holed sieve

Perforated by – foramina

Transmit nerves &Vessels

Interdental septum

Inter –radicular septum

Lamellated boneLamellar bone consists of osteons

Concentric lamellae along with central blood vessel forms an osteon

Continuous with supporting alveolar bone

Mature bone

Bundle boneTerm bundle - Sharpey’s fibreThese fibers are inserted at 90

deg angle into ABPConsists of fibrils in the

intercellular substance and are arranged at right angles to sharpey’s fibers

These fibrils are less in number compared to lamellated bone and therefore it appears dark in H&E

Silver stain

Lamina dura Radiologic name

appears as radiopaque line

Is lost

Alveolar Crest alveolus

distance b/n CEJ and free border of ABP

ABP meets cortical plates

Most cervical rim = alveolar crest

It is slightly apical to CEJ in healthy patients

If neighburing teeth is inclined

Alveolus

Rim

Floor

Alv. crest

Fundus

Supporting alveolar bone

Two Parts

Cortical Bone

Spongiosa

Supporting alveolar bone

Cortical BoneCompact bone

Forms inner &outer plates of the alveolar process

Variations:

Maxilla –thinner

Mandible -Thicker

Premolar, Molar region –Thicker

Anterior region -Thin

Buccal cortical plate – Thick

Lingual Cortical plate -Thinner

Relation to Local anaesthesia maxilla

perforated by many openingsInfiltration is sufficient

Mandible Dense cortical plateNerve Blocks required

SpSpongiosaongiosa Fills space b/n ABP and Cortical

bone

Variations;

Maxilla –More

Mandible -Less

In ant region –both jaws :

Spongiosa is absent

Cortical plate is fused with ABP

Spongy boneSpongy bone

Two types –R/AType I

Trabeculae –

Regular

Horizontal

Thick

Ladderlike

Mandible

Trajectorial pattern

Along lines of stress

Type II

Irregular

Fine/Delicate

Maxila

No trajectory pattern , More marrow space

Nutrient Canals Zuckerkandl & Hirschfeld

Interdental &Inter-radicular septum

Contain –BV, lymph vessels and nerves

Appear as radioluscent lines or shadows

Parallel to long axis of tooth

Surface structures

Ju'ga alveolaria mandibulae

Ju'ga alveolaria maxillae

Blood supply

Nerve supply

Lymphatic drainage

Bony defects• Fenestration•Dehiscence•Central buttressing•Peripheral buttressing•Osseous craters

Functions of AB•Houses the roots of teeth•Anchorage•Helps to move teeth•Helps to absorb and distribute occlusal forces•Supplies vessels to pdl•Protects developing permanent teeth•Organizes eruption of

Age changes•Alveolar sockets appear jagged and uneven

•Marrow spaces have fatty infiltration

• In Edentulous jaws•Loss of maxillary bone • Internal trabecular arrangement is more open,

•Distance b/n alveolar crest and CEJ

•Brittleness •Osteoporosis •Alveolar crest slope distally due to mesial tilting of teeth

•With loss of teeth ,resorption of alveolar ridge

Pattern of bone resorption•Maxilla •Mandible•Alv crest

Clinical considerationsMaxillary teeth Fractured tooth Abscessloss of lamina duraAB lossOrthodontic TreatmentEffect of hormones

•Proximity of AB to sinus cavities or major nerves

•Dental implants•Surgical procedures•Periodontal disease

Therapeutic considerations•Bone grafting – used to bone deposition in periodontal surgery

•Autografts, allografts , xenografts•Guided tissue regeneration – collagen is used to support natural bone formation

•Enamel matrix proteins – used as an adjunct to periodontal surgery

summary

References ORBAN'S ORAL HISTOLOGY : S.N. BHASKAR.TENCATE’S ORAL HISTOLOGYHISTOLOGY (A TEXT AND ATLAS), MICHEAL H. ROSS, WOJCIEH PAWLINAHAM’S GENERAL HISTOLOGYGLICKMANN'S CLINICAL PERIODONTOLOGY : CARRANZA.BASIC HISTOLOGY TEXT AND ATLAS- LUIZ CARLOS JUNQUEIRA, JOSE CARNEIRO

ORAL STRUCTURAL BIOLOGY : H.E.SCHROEDER. . TEXT BOOK OF HISTOLOGY : ROSS & REITH.INTERNET ACCESS

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