Salivary glands and saliva

SALIVARY GLANDS AND SALIVA
INTRODUCTION :
Saliva is a most valuable oral fluid that often is taken for granted. It is
critical in the preservation and maintenance of oral health. Saliva has also
become useful as a noninvasive systemic sampling measure for medical
diagnosis and research. Consequently, it is necessary for clinicians to have a
good knowledge base, concerning the norm of salivary flow and function.
SALIVARY GLANDS
DEVELOPMENT OF SALIVARY GLANDS
The 3 major sets of salivary glands-the parotid, the submandibular
and the sublingual-originate in a uniform manner by oral ectodermal
epithelial buds invading the underlying mesenchyme.
The parotid glands are the first to appear at the 6th
week of
intrauterine life and the inner cheek near the angles of the mouth and grow
back towards the ear. In the para-otid, or ear region, the epithelial cord of
cell branches and canalize to provide the acini and ducts of the gland. The
duct and acinar system is embedded in a mesenchymal stroma that is
organized into lobules and become encapsulated.
The submandibular salivary gland buds also appear in the 6th
week as
a grouped series forming epithelial ridges on either side of the midline in the
floor of the mouth. The epithelial cord proliferates back into the
mesenchyme beneath the developing mandible, to branch and canalize,
forming the acini and ducts of the submandibular gland. The mesenchymal
stroma separates off the paranchymal lobules and provides the capsule of
the gland.

The sublingual glands arise in the 8th
week of intrauterine, as a series
of about ten epithelial buds just lateral to the submandibular anagen. These
branch and canalize to provide a number of ducts opening independently
beneath the tongue.
A great number of smaller salivary glands arise from the oral
ectodermal and endodermal epithelium, and remain as discrete acini and
ducts scattered throughout the mouth.
SALIVARY GLANDS - GROSS MORPHOLOGY
PAROTID GLANDS
Parotid glands provide 60-65% of total salivary volume. Each parotid
gland is pyramidal in shape. The base of the pyramid being rhomboidal and
lying immediately beneath the skin. Each gland weighs 25g. A dense
fibrous capsule separates the gland from other structures.
The superficial surface of the parotid gland (The base of the pyramid)
is defined by the zygomatic arch, the external antitory meatus, and just
behind and below the angle of the mandible. The gland extends into the
groove between the mandibular ramus and sternocleidomastoid muscle to
reach the styloid process and associated muscles which separate the gland
from the internal carotid artery and jugular vein.
The external carotid artery enters the glands and divides into its
terminal branches. The facial nerve also passes through the gland, dividing
close to the anterior border. The main parotid duct (Stensen’s duct) leaves
the mesial angle of the gland to traverse over the masseter muscle and turn
abruptly to enter the buccinator muscle prior to opening into the oral cavity
in a small papilla close to the buccal surface of the maxillary first molar
tooth.

SUBMANDIBULAR GLAND :
The submandibular gland produces about 20-30% of the total salivary
volume. The glands are irregular, walnut in shape, with the superficial
inferior portion in contact with the skin and platysma muscle. Laterally, the
gland is in contact with the mandibular body and medially with the extrinsic
tongue and mylohyoid muscles. There may be a small, deeper portion of the
gland between the mylohyoid, hyoglossus and styloglossus, muscles. This
part of the gland extends forwards and inwards above the posterior edge of
the sublingual gland. After leaving the superficial part of the gland, the duct
(Wharton’s duct) passes beneath the deep part, between the mylohyoid and
hyoglossus muscles and between the sublingual gland and genioglossus
muscle to end at the summit of the sublingual papilla at the side of the
lingual frenulum. The tortuous duct is approximately 5 cm long.
SUBLINGUAL GLAND :
The sublingual glands are the smallest of the major salivary glands;
the produce 2-5% of the total salivary volume. Each is of the size and shape
of an almond and weighs 3-4 gms. The glands lie immediately beneath the
oral mucosal lining of the mouth floor, raising a small fold on either side of
the tongue.
The glands rest on the mylohyoid muscle, with the mandible lateral
and genioglossus muscle medial. This gland has a series of small ducts
(Bartholins ducts) that open on the surface of the sublingual folds on either
side of the tongue.

MINOR GLANDS (Accessory glands)
Anterior Lingual Glands
These two irregular glandular groups lie on either side of the
frenulum on the under-surface of the tongue, with several ducts piercing the
overlying mucosa.
Serons glands of von Ebner
These are small glands whose ducts open into the sulci of the
circumvallate papillae.
Lingual, buccal, labial and palatal glands :
Small glands with short ducts, producing a secretion rich in
mucoproteins are found scattered over the surface of the tongue, the inside
of the lips and cheeks, and in the mucosa covering the hard and the soft
palate.
Blood supply :
The blood supply to the parotid is derived from the facial and external
carotid arteries, with a richer vascular supply to the ductal than the acinar
system. In fact the blood flow is parallel, but in opposite direction to the
salivary flow.
The facial and lingual arteries supply the submandibular gland,
whereas the submental and sublingual arteries supply the sublingual gland.
Venous drainage of all the glands is mainly through the external
jungular vein.
Nerve supply :
The parasympathetic nerve-supply, carrying the secretomotor fibers
to the parolid gland travels in a branch of the glossopharyngeal nerve to
which synapses in the otic ganglion and passes from three with the
auriculotemporal nerve to the gland.

Both the submandibular and sublingual glands are served by
parasympathetic secretomotor fibers originating in the facial nerve, lining in
the middle ear and passing as the chordaympani to join the lingual nerve.
These fibers synapse in the submandibular ganglion and the postganglionic
fibers pass to the glands.
Symathetic fibers pass from the superior cervical ganglion with the
blood vessels to all the glands.
SALIVARY GLANDS – MICROSTRUCTURE
The structure of the salivary glands is similar to other exocrine
glands, comprising a series of secretory units (acinar cells) clustered around
a central lumen. These acini comprise the terminal or secretory end-piece of
the gland, situated fasthest from the oral cavity. They are supported by the
myoepithelial cells and a basement membrane. From each acinus the
secretions pass to a series of interconnected ducts before passing out
through the major salivary duct into the oral cavity.
Each acinus consists comprises a series of polygonal cells on a
basement membrane central around a central ductal lumen. The acinar cells
are classified histologically into two types – serous cells and mucous cells
according to their appearance after staining with eosin and heamatoxylin i.e
this in a histochemical term rather than a functional description.
Serous Cells
They stain blue these cells make up most of the acini of the parotid
gland and of von ebner. They are large and polygonal in shape. They are
characterized by a nucleus lying towards the basement membrane. The cells
contain extensive endoplasmic reticulum and many mitochondria in the
luminal portion of the cells are granules and vacuoles which fill up during
resting periods but discharge by exocytosis on stimulation some of these can
be shown to contain amylase.

The cells produce a secretion much less viscous or more serous than
the secretion of the other glands. Hence the term serous cells.
Mucous cells
Predominantly pink – staining cells. Since their staining properties
resemble those of other cells elsewhere which produce mucoid substances,
and since the secretions of these cells are viscous and rich in protein –
carbohydrate complex, they have been referred to as mucous cells.
The acinar cells of the submandibular and sublingual glands are said
to comprise mucous cells. The general form and appearance of mucous cells
is not dissimilar to that of serous cells.
Mucous cells show more areas of smooth parallel cisternae and have
larger secretory vacuoles.
DUCTS
Intercalated duct cells
The secretions pass from the acinus to a short intercalated duct: the
duct cells tend to by cuboidal, they have large central nucleus and many
mitochondria and little endoplasmic reticulum. The duct lining cells are
closely interdigitated. The contain zymogen granules, which may contribute
to stable changes in salivary composition.
Striated duct cells
The intercalated duct then pass abrupt into another short but wide,
striated duct, the striated duct are lined by cells which are much more
columnar than the cells of the intercalated duct. The cells have marked
cellular membrane interdigitations projecting towards the lumen. the striated
ducts actively resorb sodium ions from the primary acinar secretion, with
the associated capillaries then transporting the ions away from the glands
into systemic circulation.

These striated ducts then pass abruptly into two epithelial cell layered
excretory ducts and finally to the stratified squamous epithelial cell lined
terminal duct.
Although these latter excretory ducts resorb electrolytes from the
primary secretion, they are probably less efficient than the stratified duct
lining cells.
Myoepithelial cells
These cells constrict the acini and ducts to falicitate salivary secretory
flow. In myoepithelial cells the nucleus lies in a broader part of the cell and
is surrounded by mitochondria and strands of endoplasmic reticulum. The
remainder of the cells consists of longitudinally arranged myofibrils.
MECHANISM OF SALIVARY SECRETION
Stimulation of secretomotor nerves results in the release of
neurotransmitter substances i.e., acetylcoline from the parasympathetic
nerves and noradrenalinc from the sympathetic nerves. These
neurotransmitters act on membrane receptor sites on the acinar cells to
stimulate secretion.
Formation of the acinar fluid
The acinar fluid consists of water, ions, small molecules, synthesized
by the cells. This fluid arises from the interstitial fluid, which in turn arises
from the blood in the capillaries. The capillaries behave in a similar manner
as capillaries else were : hydrostatic pressure causes an outflow of water,
and small ions and molecules diffuse from the plasma.
The acinar cells behave as if freely permeable to lipid-soluble
substances and water, but much less permeable to other molecules. Entry of
glucose and amino–acids probably occurs by active transport, their
concentration in acinar fluid is low.

The ions of the acinar fluid are broadly similar to those of interstitial
fluid. Sodium and chloride concentration are similar to those of plasma and
it is probably that active transport of these two ions at the luminal
membrane is the major factor producing an osmotic forces to speed water
movement through the acinar cells. Potassium is lost from the acinar cells to
the acinar fluid on stimulation and high acinar potassium level may arise
from a cell membrane permeability when exposed to acetyle coline.
Synthesis of salivary proteins occurs at the ribosomes and the proteins
pass into the cisternae of the endoplasmic reticulum ; to be secreted from the
cell surface by exocytosis.
MODIFICATIONS OF THE ACINAR FLUID
Modification in the intercalated duct :
Physiological evidence from the animal studies suggests that the
intercalated ducts are also involved in the initial secretion which is added to
the acinar fluid ; through histologically they do not resemble cells normally
considered to show secretory activity. It is possible that the loss of
potassium from the gland which occurs on stimulation may take place here
as well as in the acinar cells.
Modification in the striated duct :
The duct system, from the beginning of the striated ducts, plays an
active part in the modification of saliva, in this area, the acinar fluid is
transformed from an isotonic, or slightly, hypertonic fluid, with ionic
concentration similar to plasma, to a hypotonic fluid, with low sodium and
chloride concentration. The sodium pump mechanism of the membrane
operate in a polarized fashion, since the massive infolding of the baeal wall
of the cells increases the pump capacity in the side. As a result, sodium is
actively transported across the cell and the concentration gradiant in thus

enhanced between the cells and the luminal fluid, resulting in diffusion of
sodium into the cells from the lumen. The active transport of sodium is
linked with active transport of potassium in the opposite direction and also
with passive diffusion of chloride to maintain the electrochemical balance.
Bicarbonate is actively secreted to the lumen in this part of the gland. The
cells behave as if largely impermeable to water, so that although salts are
conserved in the area, water is not resorbed and a hypotonic secretion
results.
Stimulation either of sympathetic or parasympathetic nerves causes
activation of the duct cells.
The resting transmembrane potential of the cells of the striated ducts
is around – 80 mv with the inside of the cell negative. On stimulation of the
glands, the transmembrane potential on the luminal side of the cells
becomes much less negative (around – 20 mv).
Modification in the distal excretory ducts :
In the distal part of the excretory ducts partial re-equilibration of
saliva with plasma occurs and concentration of ions return from extreme
values to more plasma like concentrations.
SALIVARY CONTROL
The secretion of saliva is controlled by a salivary center composed of
nuclei in the medulla but there are specific triggers for this secretion.
Afferent pathways (stimuli)
The triggers or stimuli for secretion are
Local factors
The act of chewing, the sensation of taste, the irritation of the mucous
membrane of the mouth all these act as sensory stimuli which reflexly

produce salivation. The fibers carrying sensations of taste and touch are
carried in the same nerves carrying the secretomotor fibers – i.e., the chorda
tympani fibers in the lingual nerve (which originate in the facial nerve) from
the anterior 2/3rd
of the tounge and glossophargneal nerve from the poterior
1/3 and the tounge.
The sensation of small and sight from the nose and eyes are carried
by the 1st
and 2nd
cramial nerves respectively.
Psychic stimuli
The sight of food, talking about or the noise of food preparation are
sufficient to activate the conditioned reflexes for salivary secretion. This
indicates that salivation can be influenced by higher centers,
ex: hypothalamus.
Stimulation from other organs
Esophageal irritation causes reflex salivation, although gastric
irritation leads to increased salivation as a component of the nausea /
vomiting reflex.
Central control
The afferent stimuli reach the brain and spinal cord and are finally
integrated in the cell bodies of the preganglionic secretomotor neurons.
Where efferent secretomotor impulses are generated.
The cell bodies of the parasympathetic neurons are in the nuclei of the
facial and the glossophsyngeal nerves. The area which gives salivary
response on stimulation is termed. ‘nucleus salivatorius’. The nucleus
salivatorius has been divided into two components.
Superior salivary nucleus : stimulations of which causes secretion of
submandibular and sublingual glands.

Inferior salivary nucleus : stimulation causes secretion of parotid
glands.
The cell bodies of the sympathetic nervous system lie in the lateral
columns of the first fine thoracic nerves.
The secretomotor cell-bodies, in addition receive inputs, both
excitatory and inhibitory, from other parts of the brain. Hypothalamic
activity is also associated with salivary responses.
THE EFFERENT PATHWAY
The flow of saliva is controlled entirely by nervous stimuli.
Control in exerted mainly by parasympathetic, but also by
sympathetic stimuli.
The parasympathetic fibers to the submandibular and sublingual
glands arise from the superior salivary nucleus in the medulla as nervous
intermedins and by – passing the geniculate ganglion descend downwards
through the facial (VII cranial) nerve. The chorda tympani nerve descends
downwards and reaching the cavity of the mouth meets the lingual nerve.
Then the secretory fibers leave the lingual nerve and end in the
submandibualar ganglion. From the submandibular ganglion of the post
ganglionic fibers arise and reach the submandibular and sublingual glands
and supply them with secretory and dialotory fibers.
The parasympathetic fibers to the parotid gland arise from the inferior
salivary nucleus (dorsal nucleus of the IX nerve) in the medulla and descend
downwards through the glossophargneal (IX) nerve and being separated as
the tympanic branch pass through the tympanic plexus and then through the
lesser superior petrosal nerve end ultimately in the otic ganglion. From this
the post ganglionic fibers arise and reach the parotid gland through the
auriculotemporal branch of the trigemenal (V nerve) nerve to supply it with
secretory and dilator fibers.

The sympathetic fibers to all these glands synapse in the superior
cervical ganglion. The postganglionic fibers arising from this ganglion pass
along the walls of the arteries and supply all the salivary glands. The
sympathetic fibers are believed to end in the serous gland or the serous part
of the mixed gland and supply vasoconstrictor fibers to the vessels of the
glands and myoepitheilial cells of the ducts.
SALIVA
Saliva is a wonderful, marvelously equipped fluid to protect and
preserve the oral tissues.
According to stedmans medical dictionary 26th
edition.
Saliva is clean, tasteless, odourless slightly acidic vicious fluid,
consisting of secretions from the parotid, sublingual, submandibular salivary
glands and the mucous glands of the oral cavity.
COMPOSITION OF SALIVA
Human saliva :
Total amount : 1,200 – 1500 ml in 24 hrs. a large proportion of this volume
is secreated at meal time. When the secretory rate is highest.
Consistency : slightly cloudy, due to presence of cells and mucin.
Reaction : usually slightly acidic (ph 6.02 – 7.05)
Specific gravity : 1.002 – 1.02
Feezing point : 0.07 – 0.340
c.

COMPOSITION OF SALIVA
Saliva consists of 99.5% water and 0.5% of solids
These component interact in related function in the following general areas.
1) Biocarbonates, phosphates and urea act to modulate Ph and buffering
capacity of saliva.
2) Macromolecule proteins, mucins, severe to cleanse aggregate attach
oral microorganisms and contribute to dental plaque matabolism.
3) Calcium, phosphate and proteins act together as an antisolubility
factor and modulate demineralization and remineralization.
4) Immunoglobulins, proteins, and enzymes provide antibacterial action.
Anions
SALIVA
Water (99.5%) Solids (0.5%)
Organic (0.3%)
γ-globulin
Ptyalin
Mucin
Kallikrein
Bradykymin
Lysosome
Immunoglobulin IgG
Blood group antigen
Nerve growth factor
Vit C and vit K.
Urea and uric acid.
Cellular components
Cations
Na+
K+
Ca++
Mg++
Fluoride
Cl-
HCO3
-
PO4
-
Thiocynate
Inorganic (0.3%)

Saliva is not considered as an ultrafiltrate of plasma initially saliva is
isotontic as it is formed in the acin, but it becomes hypotomic as it travels
through the duct network. The hypotonicity of the unstimulated saliva
allows the taste buds to perceive different tastes. Hypotonicity, especially
during low flow periods, also allows for expansion and hydration of mucin
glycoproteins, which protectively blanket the tissues of the mouth.
Factors Affecting The Concentration Of Salivary Constituents
Flow rate in salivary glands on individual constituents
- Substances whose concentration increase with flow rate increases
: Total protein, amylase, Na, HCO3
- Substances whose concentration decreases with the increase in flow
rate : Phosphate; Urea, aminoacids, uric acid, serum albumin.
- Substances whose concentration Does not change with change in flow
rate : Potassium (K), Fluoride
- Substances whose concentration decreases at first but increases as
flow rate increases : Cl-
, Ca++
, Protein-bound carbohydrates.
Factor affecting flow rate
Diurnal variation :
Salivary flow rates exhibit diurnal variation.
Protein concentrations tend to be high in the afternoon.
Na+
, Cl-
concentrations tend to be high in the early hours
K+
- tend to be high in the afternoons
Ca++
- tend to be high in the night
Nature of stimulus :
The stimulus may vary in its affect of different glands. Variations in
composition of whole saliva may arise from differing proportion of the
major secretions.

Dietary factors :
Functional salivary glandular activity is influenced by mechanical and
gustatory factors eg: copious salivary flow results from the smell of food or
new denture insertion.
Insufficient salivary flow results in 2 general oral-related effects :
1) Reduced preparation of food for digestion and taste
2) Increased susceptibility of oral structures to diseases.
This may be the result of salivary gland hypofunction. Hypofunction
of stimulated salivary flow is not a normal age related change.
A working knowledge of normal salivary flow is necessary for the
clinician, discussing patient home care instructions.
- Low flow during sleep, mandates the need to carefully cleanse the
mouth before going to bed and after breakfast.
- The use of sugarless chewing gum or candy containing Xylitol or
sorbitol can be recommended as a mean of stimulating extra salivary
flow to aid caries management and lubrication.
- Acidic and sweet taste stimuli are better choices as triggers for
desired extra flow.
- The successful use of removable prostheses by a patient may be
affected dramatically by decreased salivary flow.

FUNCTIONS OF SALIVA :
Salivary functions can be organized into 5 major categories that serve
to maintain oral health and create an appropriate ecological balance.
1) Lubrication and protection.
2) Buffering action and clearance.
3) Maintenance of tooth integrity.
4) Antibacterial activity.
5) Taste and digestion.
The salivary components work in concert in overlapping,
multifunctioning roles, which can be simultaneously beneficial and
detrimental.
1) Lubrication and protection :
As a seromucous coating, saliva lubricates and protects the oral
tissues, acting as a barrier against irritants. These irritants include
proteolytic and hydrolytic enzymes. Produced in plaque, potential
carcinogens from smoking and exogenous chemicals.
The best lubricating components of saliva are mucins that are secreted
from minor salivary glands. These mucins have the properties of low
solubility, high viscosity, high elasticity and strong adhesiveness. Any
intraoral contact between soft tissues, between soft tissues and teeth and
between soft tissues and prosthesis benefit from the lubricating capability of
saliva supplied largely by these mucins. Mastication speech, and
swallowing all are aided by the lubricating effects of mucins. Mucins also
perform an antibacterial function by selectively modulating the adhesion of
micro organisms to oral tissue surfaces, which contributes to the control of
bacterial and fungal colonization.
Secretions from the submandibular and sublingual glands contain
high-molecular weight mucin (MG1) and a low molecular weight mucin
(MG2). The importance of these two major mucins has been the focus of

research for the last two decades. MG1 absorbs tightly to the tooth and
thereby contributes to the enamel pellicle which protects the tooth from acid
challenges. MG2 binds to the enamel but in easily displaced. It promotes the
aggregation and clearance of oral bacteria, including streptococci mutans.
An important part of the multifunctional role of salivary mucins is
preserving mucosal integrity is their ability to regulate intercellular calcium
levels. As a part of the enamel pellicle, mucins help initiate bacterial
colonization by promoting the growth of benign commensal oral flora,
forming, a protective barrier and lubrication against excessive wear,
providing a diffusion barrier against acid penetration and limiting mineral
aggress from the tooth surface. The results of research clearly indicate that
salivary mucins performs a variety of function essential to maintaining a
stable oral defense.
2) Buffering action and clearance :
Buffering action and clearance are a second function of salvia through
the following components :
Bicarbonates, phosphate, urea, and amphoteric proteins, and enzymes,
bicarbonate is the most important buffering system. It diffuses into plaque
and acts as a buffer by neutralizing acids. Moreover, it generates ammonia
to form amines, which also serve as a buffer by neutralizing acids; low
molecular weight histidine-rich peptides. Present in saliva also act as a
buffer. Urea, another buffer releases ammonia after being metabolizaed by
plaque and thus increases plaque PH. Buffering action of saliva is more
effective during stimulated high flow rates. Phosphate is likely to be
important as a buffer only during unstimulated flow.
Thus salivary buffering, clearance, and flow rate work in concert to
influence intraoral pH.
Salivary flow can be augumented by the stimulus of chewing as well
as the muscular activity of the tips and tongue. With stimulated additional

flow, chewing products (such as gum) that contain no fermentable
carbohydrates can aid in the modulation of plaque PH. Sugar free gums
containing xylitol and sorbitol can be recommended. Indeed research has
shown that the use of gum containing xylitol or sorbitol reduces plaque
accumulation and gingival inflammation and enhances remineralization
potential.
3) Maintenance of tooth integrity :
Maintenance of tooth integrity is a third function of saliva, one that
facilitates the demineralization and remineralization process.
Demineralization occurs when acids diffuse through plaque and the
pellicle into the liquid phase of enamel between enamel crystal. Resulting
dissolution occurs at a PH of 5 to 5.5, which is the critical PH range for the
development of caries. The buffering capacity of the saliva influences the
PH of plaque surrounding the enamel, thereby inhibiting caries progression.
Remineralization is the process of replacing lost minerals through the
organic matrix of the enamel to the crystals. The high salivary
concentrations of Ca++
and PO4, may account for the maturation and
remineralization of the enamel. Proteins in the pellicle, such as statherin,
histamines, and proline rich proteins, aid in controlling crystalline growth of
enamel by allowing the penetration of minerals, into the enamel for
remineralization and limiting mineral egress.
Fluoride in the salivary solution works to inhibit dissolution of apatite
crystals. Fluoride speeds up crystal precipitation, forming a fluorapatite-like
coating more resistant to caries than the original tooth structure.
The contribution of saliva to the demineralization and
remineralization process points to the importance of monitoring salivary

flow especially in patients taking multiple medications or having systemic
entities that decrease salivary flow. For patients with incipient caries
fluoride supplements can promote remineralization. Salivary stimulants and
substitutes also should be encouraged for patients with salivary
hypofunction.
Researchers are currently investigating a method to genetically
engineer salivary proteins and other salivary components for use in future
artificial salivas.
4) Antibacterial activity :
A fourth function of saliva in antibacterial activity. Salivary glands
are exocrine glands, and as such, secrete fluid containing immunologic and
non-immunologic agents for the protection of teeth and mucous surfaces.
Immunologic contents of saliva include secretory IgA, IgG and IgM.
Non immunologic salivary contents are selected proteins, mucins, peptides
and enzymes. (lactoferin, lysosome and peroxidase).
MG2 and IgA complex bind mucosal pathogens with great affinity.
- Lactoferin, binds to ferric iron in saliva, this process makes ferric iron
unavailable as a food source for microbes, such as cariogenic
streptococci, that need iron to remain viable.
- Lysosomes, split bacterial walls, leading to destruction and inhibition
of bacterial growth.
- Peroxidase, catalyses bacterial metabolic by-products with thiocynate,
which is highly toxic to bacterial systems, peroxidase also protects
the mucosa from the strong oxidization effects of hydrogen peroxide
produced by oral bacteria.

- Cystatins, have a major role in regulation of salivary calcium.
Finally, proteins such as glycoproteins, statherins, agglutinins,
histadine-rich protein, proline-rich proteins work to aggregate bacteria, the
clumping, inhibits adhereane and colonization on to the hard or soft tissue
intraoral surfaces.
The concept of saliva’s antibacterial activity highlights the clinical
value of stimulating natural saliva especially in patients with decreased
function.
5) Taste and Digestion :
The fifth and final function of saliva is to enhance taste and begin the
digestive process. The hypotonicity of the saliva enhances the tasting
capacity of salty foods and nutrient sources.
Saliva has an early, limited role in total digestion by beginning the
breakdown of starch with amylase, a major component of parotid saliva
salivary enzymes also initiate fat digestion. More importantly saliva serves
lubricate the food bolus, which aids in swallowing. When one considers the
contribution of saliva to taste and early digestion, it becomes clear that
artificial supplements would be difficult to develop.
ARTIFICIAL SALIVA :
From the proceeding section it is clear that an adequate amount of
salivary flow is essential in the host’s resistance to dental caries and also to
vital importance in the comfortable and successful mastication and
swallowing of food. It plays a vital role in the comfort of denture wearers.
When salivary flow is reduced, salivary stimulants or artificial
salivary substitutes have been proposed. Salivary stimulants are most

satisfactory in the form of pastille, which require chewing, as chewing also
acts a stimulant. The active ingradient is acidic in nature as this is well
known to provoke salivation. For diabetic patients pastilles containing
sorbitol rather than sugar are advised.
No artificial saliva that is fully satisfactory has yet been formulated.
Both carboxymethyl cellulose and hydroxyethyl cellulose in aqueous
solutions are in common use and are used as mouthwash as frequently as
required. Neither of these materials have the viso-elastic properties of
natural saliva and both require frequent use to maintain a moist oral
environment.
A possible alternative is high molecular weight polyethylene oxide.
Although 2% aqueous solutions has similar viscoelastic properties of natural
saliva, this sticky, stringing and viscous liquid is difficult to handle. Many
artificial saliva solutions contain acid, for dental patients as the acidic
content (usually citric acid) may cause erosion of teeth, acid-free artificial
saliva is advised.
“Glandosane” a commercial mouth lubricant with a PH of
approximately 5.4 which contain carboxymethyl cellulose together with
calcium and phosphate ions in a promising product.
Saliva orthane which has a pH of 7 and is now available containing
sodium fluorides (NaF) instead of methyl cellulose it contains mucin
extracted from the gastric mucosa of pig to provide appropriate viscosity.

Artificial saliva can be classified
1) Depending on treatment approach
• Extrinsic – topically applied artificial saliva
• Intrinsic – Chemical / drug which stimulates salivary gland.
Extrinsic is divided into two groups depending upon the presence or
absence of natural mucin.
• Synthetic
• Animal.
2) According to research development.
1) 1st
generation
2) 2nd
generation
3) Disease oriented
4) Function oriented
5) Contains design.
Disadvantages :
- Poor taste
- Lack of wettability
- Cannot be selectively targeted to different parts of the oral cavity.
- Expensive

ROLE OF SALIVA IN PROSTHODONTICS
From a prosthodontist point on view, salivary glands are of great
importance anatomically and physiologically.
The submandibular gland is located in the submandibular fossa on the
lingual aspect of the mandible, and a part of the gland is wrapped around the
posterior part of the mylohyoid muscle, it is from this position wartons
ducts curves forward and open at a papilla in anterior floor of mouth lateral
to midline. Extension of the lingual flange of a denture in this region, in
such cases patient may complain of developing swellings under the jaws
when eating.
The orifice of the stensons duct opens on the mucosal fold that is
located in the cheek at the level of the crown of the 1st
molar, occasionally a
complete denture may obstruct the orifice, however the occurrence is rare.
Dentist should examine the duct and orifices to ensure they are open
and good salivary flow is evident.
Consistency and Amount of saliva :
The amount and consistency of saliva will affect the denture
construction process and the quality of the final product itself.
Consistency of saliva :
The consistency of salvia ranges from thin serous type to the thick
mucous ropy consistency.
It is best to work with the serous type, and fortunately this is more
commonly found. The thick, ropy saliva may create a problem for maxillary
complete denture rentention. Thick saliva can create hydrostatic pressure in

the area anterior to the posterior palatal seal, resulting in a downward
dislodging force exerted upon the denture base.
In an effort to alleviate this potential problem, a fine line or cupid’s
bow can be scribed on the mastee cast, anterior to the cluster of palatal
mucous glands. This extension of the posterior palatal seal line will contain
the thick mucous in the posterior part of the denture to provide a seal even if
the posterior portion of the denture base is slightly out of contact with the
palatal tissues.
Amount of salvia :
Excess amount of saliva complicates denture conduction especially
impression making.
During impression making of the maxillary arch. Palatal glands
secretion may distort the impression material in the posterior 2/3 of the
palate to counteract this
1) Palatal may be massaged to encourage the glands to empty.
2) Mouth may be irrigated with astringent mouthwash just prior to
inserting the impression material
3) The palate may be wiped with gauge.
Excessive salivation, particularly of submandibular and sublingual
glands may present a problem in impression making.
Saliva inhibiting drugs like methanthaline bromide and Atropine may
be administered.

These drugs are contraindicated in patients with
Cardiac disease
Prostate hypertrophy
Glucoma
Saliva should be controlled by mechanical means in these patients by
using saliva ejector and cotton swabs.
Dry mouth (Xerostomia)
It will affect the retention of the denture and increases the potential
for soreness in the mouth due to frictional trauma. .
Contarary to popular belief, recent studies have shown that salivary
flow does not diminish with age. However because of high incidence of
elderly patients taking medications, that have an effect on salivary flow, dry
mouth (Xerostomia) is not uncommon in the aged.
Some of the medications causing xerostomia are.
• Antihistamines
• Atropine
• Antihypertensives
• Nitroglycerine
• Anti-anxiety drugs.
• Anti-depressants

Difficulty in denture wearing is often the first sign of Sjogrem
syndrome. Although this condition is rare, the dentist must always consider
it in an elderly patient with xerostomia.
Management of xerostomia depends on the cause of its condition. If
a drug is suspected, alternate drug therapy must be discussed with the
patients physician if possible.
Sialogouges (like pilocarpine) and salivary substituted may be
(against stimulating salivary flow) recommended.
Petroleum jelly may be applied to the dentures to reduce friction
Some of the pathological conditions that decreases salivation are :
1) Senile atrophy of the salivary glands.
2) Irradiation therapy of head and neck tumours
3) Disease of the brain stem that directly depress the salivary nuclei and
block salivation.
4) Some types of encephalitis, including poliomyelitis.
5) Diabetes mellitus / Diabetes insipidus.
6) Diarrhea caused by bacteria or frod.
7) Elevated temp caused by acute infectious diseases.
8) Vitamin A deficiency.
Pathological conditions that may be accompanied by increased
salivation are :

1) Digestive tract irritants
2) Painful afflictions of the oral cavity.
RESEARCH APPLICATIONS :
Many areas of research involving salivary components and functions
are in progress for local and systemic disease diagnosis, treatment and
prevention.
The value of saliva undoubtedly will continue to increase because it
serves as a easily collected, non invasive. Source of information reflective
of the status of health in the body, salivary samples can be analysed for
1) Tissue fluid level of naturally, therapeutically, and recreationally
introduced substances.
2) Emotional status
3) Hormonal status
4) Immunologic status.
5) Neurologic status
6) Nutritional / metabolic influences.
Saliva already is used to aid in the diagnosis of dental disease.
Examples include
- Caries risk assessment
- Identification markers for periodontal disease.
- Salivary gland disease and dysfunction.
- Candida infections.
Salivary collections are used for diagnostic determinants for viral
diseases, sarcoidosis, tuberculosis, lymphoma, gastric ulcers and cancers,
liver dysfunction and sjogrens syndrome.

Saliva is also being used to monitor levels of polypeptides, steroids,
antibodies, alcohol and various other drugs.
Research currently is being conducted to determine the value of saliva
as a diagnostic aid for cancer and preterm labor.
Another area of research involves the possible regenerative properties
and functions of growth factors found in saliva. Evidence suggests that these
growth factors play a role in wound healing and maintenance of oral and
systemic health.
The multifunctional roles of salivary components continue to
represent a very focused area of dental research.
Can the reductant and synergistic effects of the salivary proteins be
used to further enhance remineralization ?
Could the salivary antibacterial factors be targeted to positively alter
the biofilm community in plaque ?
Can salivary constituents more selectively control bacterial adherence
and aggregation ?
Can the buffering system of saliva effectively and selectively be
enhanced ?
Can salivary components be reproduced or replaced by new
development in artificial saliva ?
Questions such as these are being addressed through continuing
research efforts.

CONCLUSION
The knowledge of normal salivary composition, flow and function is
extremely important on a daily basis when treating the patients.
Recognition should be given to saliva for the many contribution it
makes to the preservation and maintenance of oral and systemic health.

REFERENCES :
1) Human Physiology 11th
edition : C.C. Chattergee
2) Applied Physiology of the mouth 3rd
edition :
Christopher L.B. Lavelle
3) Applied Oral Physiology 2nd
edition : Christopher L.B. Lavelle
4) Physiology for dental study : D.B. Fergurson
5) Review of Medical Physiology 13th
edition : William Gwanong
6) Human Anatomy 10th
edition : D.B. Chaurasia
7) JPD 2001 : Vol. 85 ; 162 - 169

SALIVARY GLANDS AND SALIVA
INTRODUCTION
SALIVARY GLANDS
• Development
• Gross Morphology
• Blood supply
• Microscopic structure
• Mechanism of salivary secretion
- Formation of acinar fluid
- Modification of acinar fluid
• Salivary control
SALIVA
• Definition
• Composition of Saliva
• Factors affecting Salivary flow
• Function of saliva
• Role of saliva in prosthodontics
• Research application
CONCLUSION
REFERENCES

COLLEGE OF DENTAL SCINECES
DEPARTMENT OF PROSTHODONTICS
INCLUDING
CROWN & BRIDGE AND IMPLANTOLOGY
SEMINAR
ON
SALIVARY GLANDSSALIVARY GLANDS
ANDAND
SALIVASALIVA
PRESENTED BY :
DR. SUNEEL G. PATIL

Salivary glands and saliva

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