Salivary gland And Role of saliva in maintaining oral health

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Darpan NenavaPG 1st year

CONTENTS INTRODUCTION ANATOMY OF SALIVARY GLANDS

PAROTID GLAND SUBMANDIBULAR GLAND SUB LINGUAL GLAND

EMBRYOLOGY HISTOLOGY PHYSIOLOGY SALIVA CONCLUSION REFERENCES

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Introduction Salivary glands are group of compound exocrine

glands secreting saliva.

Parenchymal elements consists of terminal secretory units leading into ducts.

Connective tissue forms a capsule around a gland, and extend into it dividing groups of secretory units & ducts into lobes & lobules.

Tubulo acinar units are merocrine

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Introduction Salivary Gland is any cell or

organ discharging a secretion into the oral cavity. Major and minor Salivary

Glands

Major (Paired) Parotid Submandibular Sublingual

Minor Those in the Tongue,

Palatine Tonsil, Palate, Lips and Cheeks 4

Anatomy of salivary glands

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Parotid Gland Largest

Average Wt - 25gm

Irregular lobulated mass lying mainly below the external acoustic meatus between mandible and sternomastoid.

On the surface of the masseter, small detached part lies b/w zygomatic arch and parotid duct-accessory parotid gland or ‘socia parotidis’ 6

Parotid Capsule

Derived from investing layer of deep cervical fascia.

Superficial lamina-thick, closely adherent-sends fibrous septa into the gland.

Deep lamina-thin- attached to styloid process,mandible and tympanic plate.

Stylomandibular ligament.

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External Features Resembles an inverted 3 sided

pyramid

Four surfaces Superior(Base of the Pyramid) Superficial Anteromedial Posteromedial

Separated by three borders Anterior Posterior Medial

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Relations Superior Surface

Concave Related to

Cartilaginous part of ext acoustic meatus

Post. Aspect of temperomandibular joint

Auriculotemporal Nerve Sup. Temporal vessels

Apex Overlaps posterior belly of

digastric and adjoining part of carotid triangle

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Superficial Surface Covered by

Skin Superficial fascia containing facial

branches of great auricular N Superficial parotid lymph nodes and

post fibers of platysma

Anteromedial SurfaceGrooved by posterior border of

ramus of mandible

Related to Masseter Lateral Surface of

temperomandibular joint Medial pterygoid muscles Emerging branches of Facial N

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Posteromedial Surface

Related to mastoid process with

sternomastoid and posterior belly of digastric.

Styloid process with structures attached to it.

External Carotid A. which enters the gland through the surface

Internal Carotid A. which lies deep to styloid process

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Borders

Anterior border

Separates superficial surface from anteromedial surface.

Structures which emerge at this border

Parotid DuctTerminal Branches of

facial nerveTransverse facial

vessels

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Posterior Border

Separates superficial surface from posteromedial surface

Overlaps sternomastoid

Medial Border

Separates anteromedial surface from posteromedial surface

Related to lateral wall of pharynx

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Structures within Parotid Gland

External carotid A Retromandibular

Vein Facial Nerve

Superficial temporal A

Maxillary A

P.Auricular A

Superficial temporal V

Maxillary V

Post auricular VExternal jugular Common Facial V

Facial Nerve

temporal

buccal

mandibular

cervical

zygomatic

Zygomaticotemporal

Cervicofacial

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Facial Nerve trunk lies approximately 1 cm inferior and 1 cm medial to tragal cartilage pointer of external acoustic meatus.

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Parotid Duct

Ductus parotideus; Stensen’s duct

5 cm in length

Appears in the anterior border of the gland

Runs anteriorly and downwards on the masseter b/w the upper and lower buccal branches of facial N.

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At the anterior border of masseter it pierces

Buccal pad of fat Buccopharyngeal fascia Buccinator Muscle

It opens into the vestibule of mouth opposite to the 2nd upper molar

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Surface anatomy of Parotid Duct

Corresponds to middle third of a line drawn from lower border of tragus to a point midway b/w nasal ala and upperlabial margin 18

Blood supply

Arterial Branches of Ext.

Carotid A

Venous Into Ext. Jugular

Vein

Lymphatic DrainageUpper Deep cervical nodes via Parotid nodes

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Nerve Supply Parasymapthetic N

Secretomotor via auriculotemporal N

Symapathetic N Vasomotor Delivered from

plexus around the external carotid artery

Sensory N Reach through the

Great auricular and auriculotemporal N

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1. A viral inflammation of the parotid gland (mumps) causes it to swell, resulting to pain on movement of the jaw.

2. Abcesses or cysts of the gland may result in pressure to the facial nerve

3. Stones or calculi in the duct can block it, causing painful swelling of the gland.

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Clinical Consideration

Submandibular Salivary Glands

It is a mixed serous and mucous secreting gland.

Irregular in shape

Large superficial and small deeper part continous with each other around the post. Border of mylohyoid

Superficial Part Situated in the digastric triangle Wedged b/w body of mandible and mylohyoid 3 surfaces

Inferior,Medial,Lateral

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Capsule

Derived from deep cervical fascia

Superficial Layer is attached to base of mandible

Deep layer attached to mylohyoid line of mandible

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Relations

Inferior- covered by Skin Supeficial fascia

containing platysma and cervical branches of facial N

Deep Fascia Facial Vein Submandibular Nodes

Lateral surface Related to

submandibluar fossa on the mandible

Madibular attachment of Medial pterygoid

Facial Artery 25

Medial surface

Anterior part is related to myelohyoid muscle,nerve and vessles

Middle part-Hyoglossus,styloglossus,lingual nerve, submandibular ganglion,hypoglossal nerve and deep lingual vein.

Posterior Part-Styloglossus,stylohyoid ligament,9th nerve and wall of pharynx

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Deep part Small in size

Lies deep to mylohyoid and superficial to hyoglossus and styloglossus

Posteriorly continuous with superficial part around the posterior border of mylohyoid

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Submandibluar duct

Whartons duct 5 cm long Emerges at the anterior end

of deep part of the gland Runs forwards on hyoglossus

b/w lingual and hypoglossal N At the ant. Border of

hyoglossus it is crossed by lingual nerve

Opens in the floor of mouth at the side of frenulum of tongue

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Blood Supply Arteries

Branches of facial and lingual arteries

Veins Drains to the

corresponding veins

Lymphatics Deep Cervical Nodes via

submandibular nodes

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Nerve Supply

Branches from submandibular ganglion, through which it receives

Parasymapthetic fibers from chorda tympani

Sensory fibers from lingual branch of mandibular nerve

Sympathetic fibers from plexus on facial A

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Sublingual Salivary Glands

smallest of the three glands

weighs nearly 3-4 gm

Lies beneath the oral mucosa in contact with the sublingual fossa on lingual aspect of mandible.

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Relations Above

Mucosa of oral floor, raised as sublingual fold

Below Myelohyoid Infront Anterior end of its

fellow

Behind Deep part of

Submandibular gland

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LateralMandible above

the anterior part of mylohyoid line

MedialGenioglossus

and separated from it by lingual nerve and submandibular duct 34

Duct Ducts of Rivinus 8-20 ducts Most of them open directly

into the floor of mouth Few of them join the

submandibular duct

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Blood supply Arterial from sublingual and submental arteries Venous drainage corresponds to the arteries

Nerve Supply Similar to that of submandibular glands( via

lingual nerve , chorda tympani and sympathetic fibers)

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Minor salivary glands are found throughout the mouth: – Lips– Buccal mucosa (cheeks)– Alveolar mucosa (palate)– Tongue dorsum and ventrum – Floor of the mouth

Together, they play a large role in salivary production.

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Minor salivary glands

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Embryology

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PRIMORDIA TIME OF DEVELOPMEN

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EMBRYONIC ORIGIN

REGION

Parotid gland primordia (anlage)

5th to 6th week Ectoderm Labiogingival sulcus

Submandibular gland primordia

6th week Endoderm Hyoid arch

Sublingual gland primordia

7th to 8th week Endoderm Linguogingival sulcus

Intraoral minor salivary glands

3rd month

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Development of Salivary Glands

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Histology42

Compound Tubuloalveolar glands

Structure Closely packed acini or alveoli with ducts

scattered in between Supported by connective tissue which divides

the gland into lobules

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Cells lining the alveoli

Serous or mucous Serous

Stain darkly (zymogen granules)

Wedge shaped with round nucleus, lying towards the base

Mucous

Lightly stained Appears empty Polyhedral Contain mucinogen granules Nucleus flattened ,close to the

basement membrane

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Parotid Serous type

Sublingual Mucous

Submandibular Mixed type –some

mucous alveoli capped by serous cresents –

‘Demilunes’

Parotid

Sublingual

Submandibular 45

DUCTS

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DUCTS

Intralobular

ExcretoryStriatedIntercalated

Intralobular

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DUCTS

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Myoepithelial cells

Present in relation to alveoli and intercalated ducts

Those on the alveoli are branched-’Basket Cells’

Those on the ducts are fusiform

Contractile cells helps to squeeze out secretions from alveoli

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Physiology

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Main function of Salivary Gland-secretion of saliva

Daily secretion -800 to 1500 ml

pH : 6-7

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Under neural control Mainly by parasympathetic signals from Sup & Inf salivatory nuclei

Control of Salivary Secretion

Sup Salivatory Nu

Inf Salivatroy Nu

Facial NOtic Ganglion

Chorda tympani N

Submandibular G

Parotid Gland

Parasympathetic stimulation- profuse secretion of

watery saliva

Sympathetic stimulation- scanty viscid secretion

Sympathetic supply comes from cervical sympathetic chain along the blood vessels

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Salivatory nuclei are excited by

Taste and tactile stimuli from tongue and other areas of mouth and pharynx

Stimuli from esophagus and stomach (due to stimulation of vagal afferent fibers)

(unconditioned reflex)

Stimuli arising from higher centers of brain due to sight, smell or thought of food

(conditioned reflex).Pavlov with his dog54

SALIVA

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Complex fluid found lubricating the mucosa and teeth of the oral cavity.

Salivary glands, their cells and ducts are greatly responsible for the modification and kind of saliva being secreted

It is of three types: Serous Saliva Mucous Saliva Mixed Saliva

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General characteristics:

Consistency - slightly cloudy due to presence of mucins and cells

Reaction - usually slightly acidic (pH 6.02-7.05).On standing or boiling, it loses CO2 and becomes alkaline.

Specific gravity - 1.002-1.012

Freezing point - 0.07-0.34° Celsius

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Percentage contribution of different salivary glands during unstimulated saliva:

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Unstimulated flow

Resting salivary flow―no external stimuluso Typically 0.2 mL – 0.3 mL per minuteo Less than 0.1 mL per minute means the

person has hyposalivation

Hyposalivation – not producing enough saliva

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Stimulated Flow

Response to a stimulus, usually taste, chewing, or medication eg, at mealtime

o Typically 1.5 mL – 2 mL per minute

o Less than 0.7 mL per minute is considered hyposalivation

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The average person produces approximately 0.5 L – 1.5 L per day

• Salivary flow peaks in the afternoon

• Salivary flow decreases at night.

• There is a difference in the quality between stimulated and unstimulated saliva

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Ions and salivary flow

As saliva passes through the salivary ducts, cations (sodium and chloride)are reabsorbed into the adjacentblood vessels.

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As saliva passes through the salivary ducts, cations (sodium and chloride) are reabsorbed into the adjacent blood vessels. In exchange, bicarbonates and potassium are transferred from the blood

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Stimulated Salivary Flow• Saliva passes through the salivary duct very rapidly o It impedes the exchange of sodium and chloride for

potassium and bicarbonate

Unstimulated Salivary Flow• Has a high content of potassium and bicarbonate o The quality of unstimulated saliva will change when

flow increases because of a stimulus (chewing gum, thinking about lemons, looking at a food you crave)

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Saliva Compositon

Water (99.5%) Solid (0.5%)

Organic Inorganic

PtyalinMucinLysozymeIgALactoferrin

Na+K+Ca+Cl-HCO3Mg

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Ionic Composition

Saliva in the acini-isotonic with plasma

Under resting condition ionic composition of saliva reaching the mouth

Na+ and Cl- 15 mEq/l (1/7 to 1/10 conc of Plasma) K+ 30 mEq/l (7 times that of Plasma) HCO3- 50-70 mEq/l (2-3 times that of plasma)

During maximal salivation Na+ and Cl- (1/2 to 2/3 conc of Plasma) K+ (4 times that of Plasma) HCO3- 50-70 mEq/l (2-3 times that of plasma)

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Functions of Saliva

Main function: maintaining the well-being of the mouth

Other important functions: Protection Buffering Action Digestion Facilitation of Taste Defensive Action against Microbes Ionic Exchange between Tooth Surface

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Functions of SalivaEffect Active

Constituent

Protection Lubrication, lavage, pellicle formation

GlycoproteinWater

Buffering Action Regulates pH Phosphate and Bicarbonate

Digestion Digests starchDigests lipidsBolus formation

AmylaseLingual Lipase

Facilitation of Taste Taste bud growth and maturation, dissolves substances to carry to taste buds

Gustin

Defensive Action Against Microbes

AntibodiesHostile Environment

LysozymeLactoferrinIgA

Ionic Exchange Between Tooth Surface

Posteruptive Maturation of EnamelRepair

CalciumPhosphate 68

Saliva and Dental Caries

Effect of desalivation and hyposalivation on dental caries

Salivary clearance from oral cavity Flouride concentration of saliva Salivary antibacterial substance Protein inhibiting hydroxyapatite Acquired salivary pellicle

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Effect of desalivation and hyposalivation on dental caries

Total or partial aplasia is rare and accompanied by high caries prevalence

Causes Tumor growth Radiation therapy

This condition is called as XEROSTOMIA Reduced salivary secretion is called as HYPOSALIVATION Causes

Drugs such as atropine and other anticholinergics Fever or prolonged diarrhea Diabetes Anemia Hypovitaminosis A or B Uremia Dehydrating disease of old age

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Patients with hyposalivation experience Difficulty in mastication Swallowing Wearing dentures Speaking

Sjogren’s syndrome is an autoimmune Acinar cells are destroyed Dry eyes as lacrimal gland cells are also destroyed And symptoms of rheumatoid arthritis

Role of bacteria and food debris removal from oral cavity

Bacteria Bacteria is passed into stomach by salivary flow Half life of any material in cavity is only few minutes

Despite continuous flow dental plaque can accumulate at rapid rate of 10-20mg/day

Rate of plaque accumulation is even more rapid in patients with hyposalivation and xerostomia

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Salivary clearance from oral cavity

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Food Debris When retained in mouth act as substrate

for metabolic activities of microbes Thus if clearance is retarded it will tend to

promote the development of caries Caramel and other toffees show prolonged

retention Some studies show cariogenecity is not

related to sugar concentration Sugar in non retentive forms as in soft drinks

Flouride concentration of saliva The level of flouride ions in ductal saliva is as low

as 0.01-0.03ppm. Flouride level in saliva are independent of salivary

flow rate and determined by the amount ingested Fluorapatite

Insoluble in saliva Therefore beneficial to have high proportion of

fluorapatite in surface enamel as possible Higher stable concentration of fluoride can accure slowly

from saliva But can be reached more rapidly by topical flourde

applications

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Flouride concentration of saliva

The importance of fluoride maintenance and augmentation of fluoride in enamel surface

As the fluoride concentration is reduced protection against caries is also decreased

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Salivary antibacterial substance A number of anti bacterial factors present in

saliva

Lysozymes Lactoperoxidase Lactoferrin Immunoglobulin A

It helps to prevent the establishment of more pathogenic transient invaders

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Lysozymes

Have property of cleaving cell walls of microbes causing there lysis

Antibacterial action of lysozyme does not completely depend on cell lysis (Streptococcus mutans lose there viability in the

presence of lysozyme and some detergent or NaCl without lysis of cell wall

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Lactoperoxidase

This factor exists in milk, saliva and tears and can inhibit the growth and acid formation of some bacteria.

It oxidises thiocyanate (SCN-) in presence of hydrogen peroxide

Formed by microbes in hypothiocyanate(OSCN-) To oxidize thiol group which leads to activation

of many bacterial enzymes

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Lactoferrin

Bacteriocidal effects due to its strong iron binding capacity

Removing iron from solution and making it unavailable as an essential bacterial nutrient

Lactoferrin has been shown to be antagonist to S.mutans

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Immunoglobulins

There are two principal immunological mechanism involved in protection against infectious diseases Antibodies production (humoral immunity)

Antibodies produced by plasma cells circulate in body (systemic immunity)

Involving cells (cell-mediated immunity) If produced by plasma cells with secretory tissues such as salivary gland

(local immunity)

Antibodies are IgG IgA IgD IgE IgM

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Immunoglobulins

In systemic circulation IgG dominates In saliva IgA dominates in S-IgA form Secretory

Immunoglobulin A

Concentration of IgA in stimulated parotid and submandibular saliva is 4mg/100ml

30mg/100ml in secretion from minor salivary glands

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Protein inhibiting hydroxyapatite Several salivary protein bind calcium and /or

inhibit formation of hydrooxyapatite these proteins are

Statherin

Proline-Rich Proteins

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Protein inhibiting hydroxyapatite Statherin

A polypeptide Concentration in saliva 2-6 µM Also prevents precipitation of calcium phosphate from

supersaturated solution by adsorbing onto early crystal nuclei

Causing demineralization of early carious lesion Inhibition is due to the ability of the statherin to block

crystal growth of calcium phosphate

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Protein inhibiting hydroxyapatite Proline-Rich Proteins

A polypeptide Concentration in saliva 2-6 µM Also prevents precipitation of calcium phosphate from

supersaturated solution by adsorbing onto early crystal nuclei

Causing demineralization of early carious lesion Inhibition is due to the ability of the statherin to block

crystal growth of calcium phosphate

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Acquired salivary pellicle

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Acquired salivary pellicle

Clinical relevance To prevent the contact of saliva prior to composite resin

placement Upon the etched enamel Salivary protein tend to fill up defects in newly etched

enamel Pellicle thickness

100nm after 2 hrs to about 400nm in 24-48 hrs Pellicle is three layered

Subsurface :- has dendritic appearance penetrate in pores and demineralized enamel

Centre :- uniformly forms a surface around tooth Suprastructure :- variable thickness

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Acquired salivary pellicle

This is predominantly bacteria free initially Becomes highly insoluble with time due to

protein denaturation Coating becomes rapidly populated by mixed

bacterial aggregrates Grow in number and coalesce to form bacterial

dental plaque

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Properties of salivary pellicle

Act as a lubricant prevent premature loss of enamel during mastication

Reduces rate of demineralization of tooth surface by acidic food and drinks

Act as a semi permeable membrane and reduces ion mobility but the movement of water is unaffected.

Reduces mobility of calcium and phosphate from enamel to fluid enviorment

Forms a surface for bacterial colonization leads to formation of microbial dental plaque

Prevents continuous enlargement of tooth surface by crystal growth of hydroxyapatite crystal

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SalivarySalivaryFunctionsFunctions

Anti-Anti-BacterialBacterial

BufferingBuffering

DigestionDigestion

Mineral-Mineral-izationization

Lubricat-Lubricat-ion &Visco-ion &Visco-elasticityelasticity

TissueTissueCoatingCoating

Anti-Anti-FungalFungal

Anti-Anti-ViralViral

Carbonic anhydrases,Carbonic anhydrases,HistatinsHistatins

Amylases,Amylases,Mucins, LipaseMucins, Lipase

Cystatins,Cystatins,Histatins, Proline-Histatins, Proline-rich proteins,rich proteins,StatherinsStatherins

Mucins, StatherinsMucins, Statherins

Amylases,Amylases,Cystatins, Mucins, Cystatins, Mucins, Proline-rich proteins, StatherinsProline-rich proteins, Statherins

HistatinsHistatins

Cystatins,Cystatins,MucinsMucins

Amylases, Cystatins,Amylases, Cystatins,Histatins, Mucins,Histatins, Mucins,PeroxidasesPeroxidases

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SALIVATION REFLEX ACTIVITY

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Reflex Activity

Resting flow: keeps the mouth and oropharynx moist

Food and the prospect of eating: are most saliva-inducing stimuli

Whole-mouth saliva contribution when stimulated:

Parotid gland: 50% Submandibular gland: 30% Sublingual and minor salivary glands: 20%

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Reflexes

Gustatory-salivary reflex Sour>salty>sweet>bitter

Masticatory-salivary reflex Saliva flow is directly proportional to

masticatory forces Olfactory-salivary reflex

No reflex response from the parotid gland Increase in salivary secretion from the

submandibular and sublingual glands

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Reflexes

Visual and psychic salivary reflex Stimuli: thought and sight of food

Esophageal-salivary reflex Waterbrush phenomenon: sudden filling of the

mouth with fluids

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AGE CHANGES

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Age Changes

the aging salivary glands are known to undergo structural changes

The lobule structure becomes less ordered The acini vary more in size and eventually

atrophy Interlobular ducts become more prominent

and the percentage of fibroadipose tissue increases

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Age Changes

Changes in the salivary glands (submandibular,parotid (less) and minor salivary glands)Shrinkage of cellsDilation of ductsOncocytic transformationIncreased adiposityFibrosisFocal microcalcifications with obstructionChronic inflammation

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CLINICAL CONSIDERATIONS

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Mucoceles

CAUSE: trauma to excretory ducts of the minor glands which allows the spillage of mucus into the surrounding connective tissue

PHYSIOLOGIC MANIFESTATION: formation of painless, smooth surfaced, bluish lesions

TREATMENT: self-limiting (acute) or surgery (chronic)

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Mucocele

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Ranulas Type of mucocele CAUSE: blocked sublingual gland ducts PHYSIOLOGIC MANIFESTATION:

Unilateral, soft-tissue lesions, often with a bluish appearance. Vary in size and may cross the midline of the

mouth and cause deviation of the tongue TREATMENT:

self-limiting (acute)surgery (chronic)

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Ranula

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Sialolithiasis

CAUSE: inactivity of the glands Metabolic conditions that promote salt precipitation

in the glands Predisposing factors: dehydration and poor oral

hygiene PHYSIOLOGIC MANIFESTATION: formation

of caliculi TREATMENT: massaged out by a specialist,

surgery, antibiotics

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Sialolithiasis

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Necrotizing Sialometaplasia UNKNOWN CAUSE

Possible etiologic agent: smoking, trauma, vascular disease

PHYSIOLOGIC MANIFESTATION: uncommon benign lesion and inflammatory condition that affects salivary glands, usually the minor salivary glands

TREATMENT: resolves spontaneously, self-limiting

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Necrotizing Sialometaplasia

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Mumps

Aka. epidemic parotitis (viral) Occurs usually during childhood CAUSE: paramyxovirus that infects the parotid

glands PHYSIOLOGIC MANIFESTATION:

inflammation of the parotid glands located on either side of the face

TREATMENT: warm compress,warm, salt water rinses, antibiotics,surgery, anti-inflammatory medications

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Mumps

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Salivary Gland Neoplasm

Aka. Salivary gland cancer CAUSE: rapid cell growth of the salivary gland PHYSIOLOGIC MANIFESTATION: present as

painless, slow-growing masses TREATMENT: radiation therapy, chemotherapy

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Salivary Gland Neoplasms

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Irradiation Reaction (Xerostomia) subjective complaint of dry mouth due to a lack

of saliva CAUSE: tumoricidal doses of ionizing radiation,

excessive clearance or breathing through the mouth, hyposalivation (decreased saliva production)

PHYSIOLOGIC MANIFESTATION: dry oral mucosa

TREATMENT: frequent sips of water and frequent mouth care

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Xerostomia

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thank you

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