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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.