Periodontium

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Definition:

Periodontiumrefers to the specialized

tissues that both surround and support the

teeth, maintaining them in the maxillaryand

mandibularbones.

The word comes from the Greek

terms peri-, meaning "around" and -odons,

meaning "tooth”.Itprovides the support

necessary to maintain the teeth in function.

Components of Periodontium

It consists of four

principal

components namely:

.Gingiva

.Periodontal ligament(PDL)

.Cementum

.Alveolar bone

Gingiva

The gingiva covers the

alveolar bone and the

tooth root to a level

just coronal to the CEJ

TYPES :

.Marginal gingiva

.Interdental gingiva

.Attached gingiva

Mucogingival junction:

A clearly defined mucogingivalline that

demarcates the attached gingiva from the

adjacent alveolar mucosa.

Clinically the alveolar mucosa is

red,smoothand shiny unlike the gingiva

which is pink and stippled in appearance.

Histologically, the epithelium is

thinner,nonkeratinized and contains no

rete pegs.

Gingival Epithelium :

1. Oral (outer) epithelium

2. Junctionalepithelium

3. Sulcular epithelium

1) ORAL EPITHELIUM:

Covers the crest & outer surface of marginal

gingiva & the surface of attached gingiva.Averagethickness is ‘0.2-0.3mm’

2) SULCULAR EPITHELIUM:

Lines the gingival sulcus & is thin,non-

keratinized stratified.sqepi. extends from coronal limit of

JE to crest of gingival margin.

3) JUNCTIONAL EPITHELIUM:

Consists of a collarlikeband of stratified.sqepi.Lengthof JE ranges from `0.25-1.35mm’

Biological Width

The dimension of space that the healthy gingival

tissues occupy above the alveolar bone is

identified as the biological width.

clinically biologic width violation is done when the restoration margin

is placed 2mm or less from the alveolar bone ,esp.whenthe gingival

tissues are inflamed.

Periodontal ligament

Definition:

The periodontal ligament is the soft

specialized connective tissue situated

between the cementumcovering the root

of the tooth and the bone forming the socket wall.

Functions of Periodontal ligament :

.It provides a soft tissue casing to protect

the vessels and nerves from injury by

mechanical forces

.Attachment of teeth to the bone

.Maintenance of gingival tissues in their

proper relationship to the tooth

.Resistance to impact of occlusalforces

Components of the Periodontal

ligament

.The PDL consists

- CELLS

osteoblasts,osteoclasts,fibroblasts,restcells of

malassez,macrophages,undifferentiatedmesenchymalcells and cementoblasts

- AN EXTRACELLULAR COMPARTMENT

Consists of well defined collagenous fibres embedded in a non collagenous extra cellular

matrix of glycoproteins and glycolipids.

- PERIODONTAL FIBRES:

.The predominant collagens of PDL are types

1.

.They are arranged in distinct and definite fiber

bundles and are able to adapt to the continual

stresses placed on them

.The principal fibresconsists of

-alveolar crest group

-the horizontal group

-the oblique group

-the apical group

-the interradiculargroup

.All these principal fibresare embedded as

sharpeysfibresin the cementumor bone.

Principal Fibres

.The Alveolar crest fibres extend obliquely from the cementum to the alveolar crest

.The Horizontal fibres extend at right angles to the long axis of the tooth from the cementum to the alveolar bone

.The Oblique fibres extend from the cementum in a coronal direction obliquely to the bone

.The Apical fibres radiate at the apical region of the socket from the cementum to the bone

.The Interradicular Fibers Fan out from the cementum to the tooth in the furcation areas of multi

rooted teeth

Cementum:

Definition:

Cementumis a calcified

avascular tissue that

forms the outer

covering of the

anatomic tooth.

Types of cementum

-Primary (acellular)

cementum

-Secondary (cellular)

cementum

Composition of cementum:

INORGANIC:

-45 to 50% hydroxyapatite crystals

ORGANIC:

-50% organic(collagens and non collagenous

proteins)

90% is type 1& 5% type 3 collagen.

Classification of cementum

.Acellularafribrillarcementum(AAC):

-Mineralized ground substance

-No cells nor intrinsic or extrinsic collagen

-Present as coronal cementum

.Acellularextrinsic fiber cementum(AEFC):

-densely packed sharpeysfibres

-lacks cells

-found in cervical 3rdof the roots

.Cellular mixed stratified cementum(CMSC):

-contains cells,extrinsicand intrinsic fibers.

-found in the furcation area and in apical 3rdof roots

.Cellular intrinsic fiber cementum(CIFC):

-contains cells but no extrinsic fibres

-fills the resorptionlacunae

.Intermediate cementum:

-a poorly defined zone near the CEJ of teeth.

Cementoenameljunction:

Three types of joints may

exist:

-60-65%Cementum

overlaps enamel

-30% edge-edge butt

joint exists.

-5-10% where

enamel and dentin fail to

meet, leaving dentin

exposed.

Alveolar Process

Alveolar process is the portion of

maxilla and mandible that forms

and supports the tooth sockets.

It consists of,

-External buccaland lingual

cortical plate.

-Inner socket wall of compact

bone called Alveolar bone

proper,seenas lamina durain

radiographs.

-Cancelloustrabeculaebetween these two layers,whichact as a supporting alveolar

bone.