PERIODONTIUM

DR RITESH SHIWAKOTI

PERIDONTIUM

• THE PERIDONTIUM IS DEFINED AS THOSE TISSUES SUPPORTING AND INVESTING THE TOOTH THAT CONSISTS OF

1. CEMENTUM2. PERIODONTAL LIGAMENT3. BONE LINING THE

ALVEOLUS 4. PART OF THE GINGIVA

FACING THE TOOTH

PERIODONTAL LIGAMENT

• THE PDL IS THAT SOFT SPECIALIZED CONNECTIVE TISSUE SITUATED BETWEEN THE CEMENTUM COVERING THE ROOT OF THE TOOTH AND THE BONE FORMING THE SOCKET WALL

FUNCTIONS OF PDL.

• SUPPORT: PDL supports teeth in their socket. It prevents loosening of teeth.

• MASTICATORY LOAD: PDL permits teeth to withstand the considerable forces of mastication.

• SENSORY: PDL is supplied by abundant receptors and nerves that sense the movement when teeth are in function. Helps in the proper positioning of the jaws during normal function.

• NUTRITIVE: Blood vessels of ligament provide essential nutrients for the ligament’s vitality and hard tissue of cementum and alveolar bone.

• Fibroblasts, osteoblasts, cementoblasts, and even resorptive osteoclasts and macrophages require nutrition.

• CLINICAL CORRELATION: Bone, PDL, and the cementum together form a functional unit of special importance when the orthodontic tooth movement is undertaken. Orthodontic forces causes compression and constriction of blood vessels, soft tissue changes occur.

• Hence loss of alveolar bone occurs, now blood flow occurs in the spaces. And the mesenchymal cells of PDL repair the tissues.

•

• MAINTAINENCE: Tissues are maintained under the influence of heavy masticatory forces.

• ADAPTIVE ROLE

• SHOCK ABSORBER : It absorbs the shock of chewing.

PDL FORMATION

PDL is formed within the developing dental follicle.Ligament space consists of unorganized connective tissue with short fiber bundles extending into it from bone and cemental surfaces.Ligament mesenchymal cells begin to secrete collagen (mainly collagen type I).

The developing periodontal ligament fiber bundles extend into the unorganized ligament space from both the cementum surface and the surface of the alveolar bone.

PERIODONTAL FIBERS

• The predominant collagens of PDL are types I, III and XII.

• They are arranged in distinct and definite fiber bundles.

• They are able to adapt to the continual stresses placed on them.

PRINCIPAL FIBER BUNDLES OF PDL

1. THE ALVEOLAR CREST GROUPThese are attached to the cementum just below the cementoenamel junction and running downward and outward to insert into the rim of the alveolus.

2.THE HORIZONTAL GROUP2.THE HORIZONTAL GROUP

• These are just apical to These are just apical to the alveolar crest fibers the alveolar crest fibers and running at right and running at right angles to the long axis of angles to the long axis of the tooth from the the tooth from the cementum to the bone cementum to the bone below the alveolar crest.below the alveolar crest.

3. THE OBLIQUE GROUP3. THE OBLIQUE GROUP

• They are the most numerous in the PDL and running from the cementum in an oblique direction to insert into the bone coronally

4.THE APICAL GROUP:

• These are radiating from the cementum around the apex of the root to the bone forming the base of the socket.

5.THE INTERADICULAR GROUP

• Found only in the multi-rooted teeth and running from the cementum into the bone forming the crest of the Interradicular septum.

SHARPEY’S FIBERS• At each end all the

principal fibers of the PDL are embedded in the cementum or the bone and this embedded portion is referred to as the SHARPEY’S FIBERS therefore providing anchorage.

CEMENTUM

• DEFINITION:

• CEMENTUM IS A HARD, AVASCULAR CONNECTIVE TISSUE THAT COVERS THE ROOTS OF THE TEETH.

CEMENTUM• CEMENTUM is excreted by

cells called CEMENTOBLASTS within the root of the tooth.

• CEMENTOBLASTS are the formative cells of cementum.

• It is thickest at the root apex.

DEVELOPMENT OF CEMENTUM

• The development of cementum has been subdivided into

• PREFUNCTIONAL STAGE, which occurs through out root formation.

• FUNCTIONAL STAGE, which starts when the tooth is in occlusion and continues through out life.

TYPES OF CEMENTUM• CEMENTUM is classified

according to the presence or absence of cells within its matrix.

• CELLULAR CEMENTUM, which has an adaptive role in response to tooth wear and movement and is associated with repair of periodontal disease.

• ACELLULAR CEMENTUM, which provides attachment for the tooth.

A- CELLULAR CEMENTUMB-ACELLULAR CEMENTUM

PHYSICAL CHARACTERSTICS AND COMPOSITION

• COLOR: YELLOW.• HARDNESS: LESS THAN DENTIN.• COMPOSITION: ORGANIC MATRIX (50%) AND

INORGANIC ELEMENT (45-50%)• ORGANIC MATRIX: COLLAGENOUS AND NON-

COLLAGENOUS PROTEINS.

TYPES OF COLLAGEN:

• Type I Collagen is predominant in cementum, constitutes 90% of organic component of cellular cementum.

• Type III, Type XII, are also present.• Type XII is found in high concentration in PDL.• Traces of Type V, VI and XIV are also found in

cementum.

NON-COLLAGENOUS PROTEINS IN CEMENTUM

• These proteins are also associated with bone:• ALKALINE PHOSPHATASE.• BONE SIALOPROTEIN.• DENTIN SIALOPROTEIN.• OSTEOCALCIN• OSTEOPONTIN.• OSTEONECTIN.• FIBRONECTIN.• DENTIN MATRIX PROTEIN.• PROTEOGLYCANS. ETC.

ENAMEL PEARLS

• If some HERS cells remain attached to forming root surface they can produce focal deposits of enamel like structures called ENAMEL PEARLS.

• I have presented till here and skipped the rest

ORIGIN OF PDL CELLS AND DIFFERENTIATION OF CEMENTOBLASTS.

• PRECURSOR CELLS FOR CEMENTOBLASTS AND PDL: DENTAL FOLLICLE.

• REGENERATION OF PDL TISSUE: STEM CELLS & LOCAL PROGENITOR CELLS.

• CEMENTOBLASTS FORMATION: EPITHELIAL CELLS FROM HERS MAY UNDERGO EPITHELIAL-MESENCHYMAL TRANSFORMATION INTO CEMENTOBLASTS.

MOLECULAR FACTORS REGULATING CEMENTOGENESIS

• These molecules and factors:• CONTROL DEVELOPMENT.

(CEMENTOGENESIS).• MAINTAIN PDL.• REGENERATE PDL.

MATRIX PROTEINS

• BONE SIALOPROTEIN & OSTEOPONTIN.• FUNCTIONS: • CEMENTOGENESIS.• REPAIR & REGENERATION OF PDL.• OSTEOPONTIN: Regulate Mineral Growth.• BONE SIALOPROTEIN: Promotes mineral

formation on root surface.

COLLAGEN

• TYPE I COLLAGEN: Abundant in cementum as well as in PDL.

• TYPE III: Abundant during early stages of Cementogenesis. And during development and Repair.

• TYPE XII: Abundant in PDL and lower levels in Cementum.

OTHER FACTORS:

• TRANSCRIPTION FACTORS• ALKALINE PHOSPHATASE. (promote

cementogenesis).• GROWTH FACTORS. ( Insulin-like growth

factor, platelet-derived growth factor).• METALLOPROTEINASE.• PROTEOGLYCANS.( Accumulate at DCJ).

CEMENTOENAMEL JUNCTION• Relation of Cementum to Enamel

at the Cementoenamel Junction (CEJ)

• "OMG rule"• In 60% of the teeth cementum

OVERLAPS enamel.• In 30% of the teeth cementum just

MEETS enamelforming a butt joint.

• In 10% of the teeth there is a small GAP between cementum and enamel.

ALVEOLAR PROCESS.

• Alveolar process is that bone of jaws containing the sockets (alveoli) for the teeth.

• The alveolar process consists of OUTER (BUCCAL & LINGUAL) CORTICAL PLATE.

• Central bone is SPONGIOSA.

• Bone lining the alveolus is called ALVEOLAR BONE.

• Cortical plates and alveolar bone meets at the alveolar crest (1.5 -2m.m.) below the level of CEJ.

• Alveolar bone is perforated by foramina because it is vascular,.

• Nerves and vessels pass through it.

• Sometimes referred to as cribriform plate.

• Alveolar bone is referred as LAMINA DURA, radiographically, because of its increased RADIOPACITY.

• The bone directly lining the socket i.e. the inner aspect of alveolar bone is known as BUNDLE BONE.

GINGIVAL GROUP. Other groups of collagen

fibers found in the lamina propria of the gingiva collectively form the gingival ligament.

1. CIRCULAR GROUP:• These fibers form a

band around the neck of the tooth and help to bind the free gingiva to the tooth.

2. DENTOGINGIVAL GROUP:• These are the most

numerous fibers extending from the cervical cementum to the lamina propria of the free and attached gingiva.

3.DENTOPERIOSTEAL GROUP:

• Running apically from the cementum over the periosteum of the alveolar bone , these fibers insert into the alveolar process or the vestibular muscle and floor of the mouth.

4. ALVEOLOGINGIVAL GROUP

• These fibers radiate from the bone of the alveolar crest and insert into the free and attached gingiva.

5.TRANSEPTAL FIBER SYSTEM

• These fibers run interdentally from the cementum just apical to the base of the junctional epithelium of one tooth over the alveolar crest and insert into the cementum of the adjacent tooth.

• Thus they form a interdental ligament connecting all the teeth in the arch.

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