anatomy and biology of the um

8/2/2019 Anatomy and Biology of the um

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ANATOMY AND BIOLOGY OF THE PERIODONTIUM.

Gingival and periodontal diseases are infectious diseases by nature. Their

effects can be best understood with a basic background in the unique anatomy

of the periodontium.

Periodontium can be defined simply as tissues that surround, support and are

attached to the teeth.

These include:Gingiva.

Periodontal ligament.

Cementum.

Alveolar bone.

Maintaining the health and function of the periodontium is the most significantfactor in the longevity of the dentition

GINGIVAIs the visible component of the periodontium inside the mouth

Its one of the soft tissues that lines the oral cavityDescribed as pink, pale pink, or coral pink

In some cases it has a normal variation and melanin pigmentation

It includes the:Oral epithelium

Sulcular epithelium

Junctional epithelium

Functions

Attaches oral mucous membrane and dental hard tissues

Protects perio tissues from invasion by bacteria

Macroscopic anatomy

Oral mucosa consists of:

Masticatory mucosa

Incl gingival and hard palate

Attached to underlying boneCovered with keratinised/ parakeratinized epithelium

(Contains keratin, a schleroprotein)


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Specialized mucosa

Covers dorsum of tongue

Lining mucosa

Loosely attached to underlying structuresNon-keratinised epithelium

Covers lips, cheeks, fl of mouth, ant/ventral surface of tongue, soft

palate, uvula and alveolar mucosaAlveolar mucosa starts at mucogingival junction

Brighter red in colourMucogingival junction variable, grossly indistinct

- Histologically distinct line

- Marks separation of gingival tissue from oral

mucosaThe gingiva can be divided into three parts:

1. Free (marginal) gingiva,

Surrounds the toothCreates a cuff or collar of gingival that extends 1.5 mm coronally

Distinguished from attached gingival by free marginal groove

FMG is a slight depression on the gingival that corresponds to the

depth of sulcus

2. Attached gingiva

Apical to free gingival

More firmly attached to bone by collagen fibres

Bound to bone in form of mucoperiosteum

MP is periosteum that has mucous surface

Attached gingival extends coronally from mucogingival line

Width of attached gingiva varies from individual to individual

Commonly stippled

3. Interdental gingiva(located between adjacent teeth)

Spaces between teeth in contact

Triangular in shape

Papillae are gingival that fills embrasures (spaces)

When papillae is broad (posterior teeth) youll find a col area

COL is a slight depression (concavity) of tissue between buccal andlingual interdental papillae

It indicates a fusion of two papillae to cover a wider space


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Shape of papillae is determined by:

Contact relationships between teeth

Width of approximal surfaces

Course of CEJ

When adjacent teeth do not contact each other, attached gingivalforms between teeth, then papillae and col are absent

Microscopic anatomy

Oral epithelium

The epithelium covering the free gingiva consists of

1.Oral epithelium. Also called outer gingival epithelium2.Oral sulcular epithelium. Forms covering of soft tissue wall of gingival

tissues/extension of oral epit. Into gingival sulcus3.Junctional epithelium. Place of coming together of different types of

tissues

OE is composed of attached gingival, papillae and outer surface of free gingivalFunction is protective


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Keratinisation when surface cells form scales of keratin and lose their

nuclei

Parakeratinisation when epithelium shows signs of being keratinised, but

cells of superficial layers retain their nuclei

The oral epithelium is a stratified squamous epithelium

Stratified disposed in layers

Squamous epithelium epithelium composed of flattened plate like cells

Composed of1.keratinocytes-epidermal cells, which synthesizes keratin

2. Non-keratinocytes.

It is divided into (Fig.4):

Basal cell (stratum basale). - Situated near a basePrickle cell (stratum spinosum).

Granular cell (stratum granulosum). -Presence of granules or grainsKeratinised layers (stratum corneum).

Also contains the following cell types:

Melanocytes.

Found in basal cell layer

Produces melanin

Found gingiva, lips, buccal mucosa, and soft palate.


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Pigmentation of mouth & kin not necessarily same

Langerhans cells.

Found in more superficial cells

Part of immune systemTraps antigens on long dendritic (branched like a tree

processes & presents them to lymphocytes

Non-specific cells

Junctional epithelium (JE)

It separates the periodontal ligament from the oral environment

Its function is protection for the attachment of the tooth to the surrounding

environmentAmelocemental junction where apical limit is foundVia hemidesmosomes it is attached to the tooth surface

Oral sulcular epithelium. Is distinguished from the JE under microscopeNeutrophils- are present in small numbers

Passes through gingival crevicePlays a role in host defence

Turnover of 4-11 days. JE has rapid turnoverReadily permeable- Is r/p to substances

Principal function- TO MAINTAIN ATTACHMENT OF JE TO TOOTHSURFACE

The basement membrane (BM)

Comprises / consists of:The lamina lucida - electron lucent zone

The lamina densa -electron dense zone

From electron dense zone

Anchoring fibres

Branch out in

Fan shape

Into

Connective tissue


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The cell membrane facing

Electron lucent zone

Harbour hemidesmososmes

Are involved in attachment of epithelium

To

Underlying basement membrane

Differentiation. - Process of acquiring completely individual characters

Cells divide ( basal layer)

Move

Through epithelium

To surface

Are shed

Shapes change at surface

Become flat

Dento - gingival epithelium (DGE)

Consists of epithelium facing tooth

Non keratinised

Stratified sqaumous epithelium

It is mechanically very strong


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DGE is

subdivided into 2 parts

1.Sulcular part (sulcular epithelium)

Found at level of free gingival

Forms gingival crevice

Healthy mouth 1-2 mm

2.Junctional epithelium (JE)

Adheres to tooth surface

Squeezed between enamel facing and connective tissue

facing

Its continuous with each other

Gingival connective tissue

Connective tissue beneath gingival called lamina propria

Lamina propria made up of 2 layers:

Papillary layer immediately beneath epithelium

Reticular layer extends to periosteum

60% - CF / 5% - F / 35% - V; N; M

Cell types! Fibroblasts; mast cells; macrophages; neutrophils; granulocytes;lymphocytes; plasmacells

Connective tissue fibres produced by fibroblasts

Can be divided into:

Collagen fibres.

Reticulin fibres.

Oxytalan fibres.

Elastic fibres.


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Collagen fibres are arranged ingroupsand together form a fibrous cuff around

the tooth (Fig.6):

Circular fibres (CF)

Encircles tooth coronal to the alveolar crest

They support free gingiva

Trans-septal fibres (TF)

Attached at most coronal portion of adjacent teeth

Ends are inserted into cementum of teeth

Probably helps maintain he relationships betweenteeth

Dento-gingival fibres (DGF)

Radiates from cementum into free & attached gingival

Probably supports the gingiva

Dento-periosteal fibres (DPF)

Goes from cementum across to the alveolar crest

May anchor tooth to bone and protect periodontalligament

Crestal fibres.

From the alveolar into attached gingival

Probably attaches gingiva to bone


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PERIODONTAL LIGAMENT (PDL)

PDL Provides sensory cushion between surface of tooth and bone

-Rich nerve supply

-Vascular (indicative of copious blood supply)

-Is a connective tissue complex primarily filled with fibre bundles and

cells?- Contains cells which give rise to cementum and alveolar bone- Specific functions of ligament includes:

1. Tooth anchorage

- Attaches tooth to bone

- Acts as a shock absorber- Transmits tension to alveolar bone when

occlusal forces are generated2. Fibrous tissue development and maintenance

3. Calcified tissue development and maintenance4. Nutritive and metabolite transport

- Blood supply carries nutrients to the area

5. Sensory functions, incl. Touch, pressure, pain, and

proprioception (displacement sensitivity)

- Proprioceptive receptors plays NB role in monitoring

mandibular function

Fibre bundles

Are made of collagen

Attach tooth to bone

Are also believed to: transmit occlusal forces to bone

Resist occusal forces (shock absorber effect)

Protect vessels and nerves from injury

Are five principle fibre bundles

Are attached to cementum with brush like fibres called Sharpeys fibres

SF goes from cementum across periodontal ligament and terminates in thealveolar bone as Sharpeys fibres


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Fibre bundles include:

Alveolar crest fibres (ACF)

Runs from cementum to ridge of ridge of alveolar bone

Are thought to oppose lateral forces

Also to retain tooth in boneHorizontal fibres (HF)

Runs horizontally between alveolar bone and cementumApical Fibres (APF)

Runs from apex of root into alveolar bone

Both apical and lateral to root apexDo not occur in partially erupted teeth

Oblique fibres

Run in an oblique direction across periodontal ligament spaceinto alveolar bone

Are largest groupAre believed to transform occusal stresses on to alveolar

boneInteradicular fibres

Only present in multirooted teeth

Spreads apically into bone, from the furcation

In addition there are also:

Collagen fibres- runs in all directions in periodontal ligament

Referred to as indifferent fibre plexus

Function is unknown


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Fig.7 Periodontal ligament fibres.

Oxytalan fibres found in PDL

Are elastic fibres, which are inserted into cementum

Function not really known

Seen in teeth that bears abnormal loads

May be associated with preservation of blood vessels

The principal cells found in the PDL include:

Undifferentiated mesenchymal cells. *

Fibroblasts. * * Involved in destruction of &

formation of PDL, Cementum, alveolar bone proper

tissues

Osteoblasts. *

Osteoclasts. *

Cementoblasts. *

Epithelial rests of Malassez.


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Epithelial rests of Malassez (remnants of Hertwig's root sheath)

Function unknown

Possibly maintains integrity of PDL

Prevents ankylosis (prevents fusion)

ROOT CEMENTUM

Is a calcified structure?

Covers entire root surface

Is avascular there are no vascular or nerve connections

So the cementum cannot transmit pain sensations

It anchors teeth

Maintains occlusal relationships

Firmly bound to the underlying dentineDoes not undergo physiological resorption and remodelling.

Acellular or primary cementum

It covers the entire root surface.

Characterized by dense layers of calcified collagen fibres

Runs II to long axis of tooth

Cellular or secondary cementum

forms after tooth eruption

responds to functional demands found near the apex of the tooth

Laid down on top of the primary cementum throughout the functional / final

period of the tooth.

ALVEOLAR BONE

Lines the sockets of teeth

Provides bony support for the sockets

## Alveolar process is the support system of teeth

It consists of cancellous (medullary) bone covered by a thin of layer of

compact (cortical bone).

The fibres of the PDL inserts into the alveolar bone.

It can re-model in response to functional demands.


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In fact is in constant state of remodelling

Remodelling accommodates the

- Physiologic tooth migration

- Bone apposition

-Resorption that are constantly occurring at aslow rate

Alveoli

Are tooth sockets

Accommodates the roots of teeth

Alveolar bone properor the cribriform plate,

Lines the alveoli

Have thousands of pores through which the tooth and PL aresupplied with nerves and blood vessels

Supporting alveolar bone.

Surrounds alveolar bone proper or cribriform plate

Interproximal boneor the interdental septum.

Bone found between roots of adjacent teeth

Interradicular bone.

Bone found between roots of multirooted teeth

Radicular bone.

Alveolar process found on facial or lingual surfaces of roots

There are 2 variations of normal bone structure that are non-pathogenic and

of importance to periodontal health. They are:

1. Dehiscence

2.Fenestration

These areas have no alveolar bone

So course of periodontal disease differs from other areas


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DEHISCENCE

A resorbed area of bone over facial surface of root

FENESTRATION

An isolated area (window or opening) in bone, which covers thefacial surface of a root

PDL, CEMENTUM & ALVEOLAR BONE ARE COMMONLY REFERRED TO AS

THE ATTACHMENT APPARATUS

Fig.8 Buccal view of the alveolar process.

BLOOD SUPPLY OF THE PERIODONTIUM

Supra-periosteal vessels SUPPLIES BLOOD TO GINGIVA

Are terminal branches of?

Sublingual,

Mental,

Buccal


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Facial,

Greater palatine

Posterior superior dental arteries.

LYMPHATIC SYSTEM OF THE PERIODONTIUMLymphatic supply parallels that of vascular

I.e. Supply to gingival and periosteal tissues

Major portion of lymph drainage goes to submandibular nodes

NERVES OF THE PERIODONTIUM

Innervation (distribution or supply) of gingiva is derived from:

1. Maxillary and mandibular branches of the trigeminal nerve.2. The buccal gingiva (maxillary posterior teeth) - supplied by the superior

alveolar nerve,

3. Facial gingiva (maxillary incisors / cuspids) - supplied by the labial branch

of the infra-orbital nerve.

4. The nasopalatine nerve supplies - palatal gingiva of the maxillary anterior

teeth

5. Anterior palatal nerve supplies - -maxillary posterior teeth.

6. The buccal gingiva (mandibular molars / premolars) - supplied by the long

buccal nerve,

7. Facial gingiva - supplied by the mental nerve.

8. The lingual gingiva (all the mandibular teeth)- supplied by the lingual

nerve.

anatomy and biology of the um

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