INTRODUCTION
Saliva is
a most valuable oral fluid that often is taken for granted. It is critical to
the preservation and maintenance of oral health, yet it receives little
attention until quantity or quality is diminished.
Saliva is a complex fluid, produced by the salivary
glands. It is a heterogeneous fluid comprising proteins, electrolytes, small
organic molecules & compounds transported from the blood, constantly bathes
the teeth & oral mucosa.
Saliva is one of the most important fluids in the human
body. Its status in the oral cavity is
at par with that of blood i.e. to remove waste , supply nutrients and
protection of cells.
It acts as a
cleansing solution, an ion reservoir, a lubricant & a buffer.
In addition to its other host - protective properties,
saliva could constitute a first line of defense against free radical-mediated
oxidative stress, since the process of mastication & digestion of ingested
foods promotes a variety of reactions, including lipid peroxidation.
Individuals with a
deficiency of salivary secretion experience difficulty in eating, speaking,
swallowing & become prone to mucosal infections & rampant caries.
Saliva is composed of more than 99% water and less than
1% solids , mostly electrolytes and proteins, the latter giving saliva its
characteristic viscosity. Normally the daily production of whole saliva ranges
from 0.5 to 1.0 litres.
90% of the whole saliva is produced by three paired major
salivary glands
Parotid Gland
Submandibular gland
Sublingual gland
CLASSIFICATION
1.Based on anatomic location
·
Parotid gland
·
Sub mandibular gland
·
Sub lingual gland
·
Accessory glands (labial, lingual, palatal
buccal,glossopalatine and retromolar)
2. Based on size and amount of secretion
·
Major salivary glands
·
Minor salivary glands
3. Based on type
of secretion
·
Serous
·
Mucous
·
Mixed
Parotid glands -
Purely serous
Submandibular-Predominantly
serous, Mixed
Sublingual - Predominantly mucous , Mixed
Labial,Buccal,Lingual{Ant.}-
Predom. Mucous , Mixed
Palatine,Glossopalatine
- Purely mucous.
Posterior part of
the tongue - Purely mucous
Von Ebner’s Glands
- Purely serous
COMPOSITION
Saliva is composed of a variety of electrolytes, including
sodium, potassium, calcium, magnesium, bicarbonate, and phosphates.
Also found in
saliva are immunoglobulins, proteins, enzymes, mucins, and nitrogenous
products, such as urea and ammonia.
These components interact in related function in the
following general areas:
(1) bicarbonates, phosphates, and
urea act to modulate pH and the buffering capacity of saliva; (2) macromolecule
proteins and mucins serve to cleanse, aggregate, and/or attach oral
microorganisms and contribute to dental plaque metabolism;
(3) calcium, phosphate, and proteins
work together as an antisolubility factor and modulate demineralization and remineralization;
(4) immunoglobulins, proteins, and
enzymes provide antibacterial action.
Salivary components, particularly proteins, are
multifunctional (performing more
than 1 function)
redundant (performing similar functions but to
different extents)
amphifunctional (acting both for and against
the host).
Saliva is a very dilute fluid, composed of more than
99% water.
Saliva is not considered an ultrafiltrate of plasma.
Initially,
saliva is isotonic, as it is formed in the acini, but it becomes hypotonic as
it travels through the duct network.
The hypotonicity of unstimulated saliva
·
allows the taste buds to perceive different tastes
without being masked by normal plasma sodium levels.
·
Hypotonicity, especially during low flow periods, also
allows for expansion and hydration of mucin glycoproteins, which protectively
blanket tissues of the mouth.
·
Lower levels of glucose, bicarbonate, and urea in
unstimulated saliva augment the hypotonic environment to enhance taste.
The normal pH of saliva is 6 to 7, meaning that it is
slightly acidic. The pH in salivary flow can range from 5.3 (low flow) to 7.8
(peak flow).
Major salivary glands contribute most of the secretion
volume and electrolyte content to saliva, whereas minor salivary glands
contribute little secretion volume and most of the blood-group substances.
FUNCTIONS
PROPERTIES OF SALIVA
• Consistency
: Slightly cloudy
• Reaction
: Usually slightly acidic
• PH
: 5-8
• Specific
gravity : 1.0024 – 1.0061
• Freezing
point :0.07 – 0.34 degree Celsius
• Osmotic
pressure : ( 700-1000m osmol/litre
)
TIME
OF ORIGIN
STAGES OF DEVELOPMENT
• STAGE
I-Bud formation:
1.
Induction of proliferation of oral epithelium by
underlying mesenchyme.
2.
Individual salivary glands arise as a
proliferation of oral epithelial cells, forming a focal thickening that grows
into the underlying ectomesenchyme.
3.
These long epithelial cords undergo repeated
dichotomous branching, called, “Branching morphogenesis”, that produces successive
generations of buds & a hierarchial ramification of the gland & the mesenchymal cells condense
around the bud.
·
STAGE II:Formation and growth of
epithelial cord
·
STAGE III: Initiation of
branching in terminal parts of epithelial cord and continuation of glandular
differentiation.
·
STAGEIV: Dichotomous branching of
epithelial cord and lobule formation.
1.
The
development of a lumen within the branched generally occurs first in the distal
end of the main cord & finally in the central portion of the main cord.
2.
The lumen
form within the ducts before they develop within the terminal buds.
3.
Some
studies have suggested that lumen formation may involve the apoptosis of
centrally located cells in the cords.
·
STAGE V:Canalization of presumptive
ducts.
1.
Following
development of the lumen in the terminal buds, the epithelium consists of two
layers of cells.
a)
The cells
of the inner layer eventually differentiate into the secretory cells of the
mature gland, mucous / serous.
b)
Some cells
of the outer layer form the contractile myoepithelial cells that are present
around the secretory end pieces & intercalated ducts.
2.
As the
epithelial parenchymal components increase in size & number, the associated
mesenchyme ( connective tissue ) is diminished, although a thin layer of connective tissue remains, surrounding each
secretory end piece & duct of the adult gland.
·
STAGE
VI:
Cytodifferentiation.
Cells of ® Terminal tubule cell ® Proacinar cells®Acinar cells
Bulb region ¯
Intercalated duct
cell
• Septa ( Thicker partitions of the
connective tissue ) which are continuous with the connective tissue capsule
surrounding the gland parenchyma into lobes & lobules & carry the blood
vessels & nerves that supply the parenchymal components & the excretoryducts.
The cells of the secretory end pieces & ducts attain
maturity during the last 2 months of gestation.
The glands continue to grow post natally with the volume
proportion of acinar tissue increasing & the volume proportions of ducts
connective tissue & vascular elements decreasing upto 2 years of age.
MORPHOLOGIC CHARACTERISTICS OF MAJOR SALIVARY GLANDS
Parotid gland
Ø Largest
of all the salivary glands
Ø Purely
serous gland that produce thin , watery amylase rich saliva
Ø Superficial
portion lies in front of external ear & deeper portion lies behind the
ramus of mandible
Ø Stensen's Duct (Parotid Papilla) opens out adjacent to maxillary second molar.
Submandibular Gland
Ø
Second
largest salivary gland
Ø
Mixed gland
Ø
Located
in the posterior part of floor of mouth,adjacent to medial aspect of
mandible & wrapping around the posterior border of mylohyoid muscle.
Ø
Wharton's
Duct opens beneath the
tongue at sub-lingual caruncle lateral to the lingual frenum
Sublingual Gland
Ø Smallest
salivary gland
Ø Mixed
gland but mucous secretory cells predominate.
Ø Located
in anterior part of floor of mouth between the mucosa and mylohyoid muscle
Ø Opens
through series of small ducts (ducts of rivinus) opening along the sub-lingual
fold & often through a larger duct (bartholin’s duct)
The minor salivary glands:
Ø
Estimated numbers is 600-1000.
Ø
Exist as small,discrete,aggregates of secretory
tissue present in the submucosa through out most of the oral cavity, except the
gingival & anterior part of the hard palate.
Ø
Predominantly mucous glands,except for Von Ebners glands(purely serous)
Ø
Here intercalated & striated ducts are
poorly developed.
VASCULAR SUPPLY
PAROTID GLAND
Arterial: Ext.Carotid Artery and its branches
Venous: Ext.Jugular
Vein
Lymphatic: Parotid Nodes® Upper deep cervical nodes
SUBMANDIBULAR GLAND
Arterial: Facial
Artery , Lingual Artery
Venous:
Common Facial Vein /Lingual Vein
Lymphatic: Submandibular Lymph
nodes
SUBLINGUAL GLAND
Arterial: Lingual
and Submental Arteries
Venous: Lingual
Vein
INFLUENCE OF BLOOD SUPPLY ON SALIVARY
SECRETION
q
Extensive
blood supply is required for rapid salivary secretion.
q
Salivation
indirectly dilates blood vessels providing increased nutrition.
q
Large increase in blood flow accompanies
salivary secretion.
INNERVATION
Parasympathetic innervation to major salivary glands
} Otic
ganglion suplies the parotid gland.
} Submandibular
ganglion supplies the other major glands.
Sympathetic innervation
Promotes the
flow of saliva and stimulates muscle contraction at salivary ducts
REGULATION OF SALIVARY SECRETION
The secretion of saliva is controlled by a salivary
center composed of nuclei in the medulla.
Three types of
triggers, or stimuli, for this production are
·
mechanical (the act of chewing),
·
gustatory (with acid the most stimulating trigger and
sweet the least stimulating),
·
olfactory (a surprisingly poor stimulus).
Other factors affecting secretion include
·
psychic factors such as pain,
·
certain types of medication
·
various local or systemic diseases affecting the
glands themselves.
Salivary glands
are innervated by both sympathetic and parasympathetic nerve fibers.
·
When sympathetic innervations dominate, the secretions
contain more protein from acinar cells,
·
parasympathetic
innervations produce a more watery secretion.
SALIVARY GLAND STRUCTURE
Composed of
parenchymal elements supported by connective tissue
The types of
cells found in the salivary glands are duct system cells, acinar cells, and
myoepithelial cells.
•
Intercalated duct : main duct
connecting acinar secretions to rest of the gland, not involved in
modification of electrolytes
•
Striated duct: electrolyte regulation in resorbing sodium
•
Excretory duct: continuing sodium resorption and secreting
potassium
•
Inter cellular canaliculi : These are the extensions of the lumen of the end piece between adjacent
secretory cells that serve to increase the terminal surface area available for
secretion.
•
Secretory end pieces:
branched ducts, terminating in spherical or tubular secretory end
pieces/ acini.
Secretory cells: There are two types of secretory cells.
1.serous cells
2.mucous cells
These two cells
differ in structure, as seen in classical histologic & electron microscopic
analyses, & in the types of macromolecular components that they produce
& secrete.
1.SEROUS
CELLS:
a) These are
spherical, consisting of 8-12 cells surrounding a central lumen.
b) Cells are pyramidal with a broad base adjacent
to the connective tissue stroma & a narrow apex forming part of the lumen
of the end piece.
c) The lumen
usually has finger like extensions located between adjacent cells called inter
cellular canaliculi.
d) Spherical
nuclei are located basally, occasionally binucleated cells are seen.
e) Secretory
granules in which macromolecular components of saliva are stored, are present
in the apical cytoplasm.
f) These cells are joined by intercellular
junctions.
a.Zonula occludens( tight junction)
b.Zonula adherens(Adhering junction)
c.Macula adherens(desmosome)
Tight junctions
exhibit a selective permeability, allowing the passage of certain ions &
water.
These cells are
attached to the basal lamina & the underlying connective tissue by
hemidesmosomes.
2.MUCOUS
ACINI:
a) These have a
tubular configuration.
b) When cut in
cross section, these tubules appear as round profiles with mucous cells
surrounding a central lumen of larger size than that of serous end pieces
c) Mucous end
pieces in the major salivary glands & some minor salivary glands have
serous cells associated with them in the form of a demilune or cresent covering
the mucous cells at the end of the tubule.\
d) The most
prominent feature of the mucous cell is the accumulation in the apical
cytoplasm of large amounts of secretory product (mucus), which compresses the
nucleus & endoplasmic reticulum & golgi complex against the basal cell
membrane.]
e) Unlike serous
cells, however, mucous cells lack intercellular canaliculi, except for those
covered by demilune cells.
3.MYOEPITHELIAL CELLS:
a)These are
basket shaped cells, contractile in nature & are associated with the
secretory end pieces & intercalated ducts of the salivary glands.
b) They are
located between the basal lamina & the secretory/duct cells & are
joined to the cells by desmosomes.
c) These are
similar to the smooth muscle cells but are derived from the epithelium.
d) Contraction of
the myoepithelial cells is due to actin & myosin, which helps to provide
support for the end pieces during active secretion of saliva.
e) These may help
to expel the primary saliva from the endpiece into the duct system.
f) They provide
signals to the acinar secretory cells that are necessary for maintaining cell
polarity & the structural organization of the secretory end piece.
g) They produce a
no. of proteins that have tumour suppressor activity, such as proteinase
inhibitors ( ex : tissue inhibitor of metalloproteinases ) &
antiangiogenesis factors
h) provide a
barrier against invasive epithelial neoplasms.
FORMATION OF SALIVA
The salivary glands are composed of specialized
epithelial cells, and their structure can be divided into two specific regions:
the acinar and ductal regions.
The acinar region is where fluid is generated and most
of the protein synthesis and secretion takes place. Amino acids enter the
acinar cells by means of active transport, and after intracellular protein
synthesis, the majority of proteins are stored in storage granules that are
released in response to secretory stimulation (Young and Van Lennep, 1978; Castle,
1993).
Three models have been described for acinar fluid secretion
1. active
transport of anions into the lumen and passage of water according to the osmotic
gradient from the interstitial fluid into the salivary lumen (Turner et al.,
1993).
2. The
initial fluid is isotonic in nature and is derived from the local vasculature.
3. While
acinar cells are water-permeable, ductal cells are not.
Ductal cells actively absorb most of the Na+ and Cl-
ions from the primary salivary secretion and secrete small amounts of K+ and
HCO3 - and some proteins.
The primary salivary secretion is thus modified, and
the final salivary secretion as it enters the oral cavity is hypotonic (Baum, 1993).
The autonomic nervous system (sympathetic and
parasympathetic) controls the salivary secretion. The signaling mechanism involves
the binding of neurotransmitter (primarily acetylcholine and norepinephrine) to
plasma membrane receptors and signal transduction via guanine
nucleotide-binding regulatory proteins (G-proteins) and activation of intracellular
calcium signaling mechanisms (for reviews, see Baum, 1987, 1993; Ambudkar,
2000).
SALIVARY GLAND SECRETIONS
Saliva can be considered as gland-specific saliva and whole
saliva.
Gland-specific
saliva can be collected directly from individual salivary
glands: parotid, submandibular, sublingual, and minor salivary glands. Useful
for the detection of gland-specific pathology, i.e., infection and
obstruction.
Whole
saliva (mixed saliva) is a mixture of oral fluids and includes secretions
from both the major and minor salivary glands, in addition to several
constituents of non-salivary origin, such as gingival crevicular fluid (GCF),
expectorated bronchial and nasal secretions, serum and blood derivatives from
oral wounds, bacteria and bacterial products, viruses and fungi, desquamated
epithelial cells, other cellular components, and food debris. Used when salivary analysis is used for the
evaluation of systemic disorders.
Saliva can be collected with or without stimulation.
Stimulated
saliva is collected by masticatory action (i.e., from
a subject chewing on paraffin) or by gustatory stimulation (i.e.,
application of citric acid on the subject's tongue; Mandel, 1993).
Unstimulated
saliva is collected without exogenous gustatory,
masticatory, or mechanical stimulation.
COLLECTION OF SALIVA
•
Non invasive, non painful techniques exist to
collect whole saliva, as well as saliva from the individual major & minor
salivary glands .
•
Whole
saliva is easily obtained & is in most case a good indicator of whole mouth
dryness.
•
Diseases
of salivary gland can often be diagnosed from the secretions obtained directly.
•
The quantification of salivary output is
referred to as sialometry.
University of Southern California School of Dentistry
guidelines
• Unstimulated
whole saliva collection always should precede stimulated whole saliva
collection.
• The
patient is advised to refrain from intake of any food or beverage (water
exempted) one hour before the test session.
• Smoking, chewing gum and intake of coffee also
are prohibited during this hour.
• The
subject is advised to rinse his or her mouth several times with distilled water
and then to relax for five minutes.
• Keep
his mouth slightly open and allow saliva to drain into the tube.
• Should
last for five minutes
Collection Of
Stimulated Saliva
• Paraffin
method (Masticatory stimulus ): Ask the patient to hold a piece of paraffin
in his or her mouth until it becomes soft ( about 30 seconds) & then to
swallow the saliva which has collect in his mouth. Now the patient is asked to
chew the piece of wax in his usual manner of chewing for exactly 2 minutes
& then to expectorate the accumulated saliva into the receiving vessel .The
volume of saliva is read off the vessel & flow is expressed as ml/min.
• Citric
Acid method ( Gustatory Stimulus ): A 2% solution of citric acid is swabbed
on to the laterodorsal surface of the tongue every 30 seconds for a period of 2
min & then saliva is expectorated into the receiving vessel. As in the
paraffin method, the whole procedure is repeated twice more, for a total time
of 6 mins. As before, the flow is expressed as ml/min.
SALIVARY FLOW RATE
There is great variability in individual salivary flow
rates.
The accepted range of normal flow for unstimulated
saliva is anything above 0.1 mL/min.
For stimulated saliva, the minimum volume for the
accepted norm increases to 0.2 mL/min.
Any unstimulated flow rate below 0.1 mL/min is
considered hypofunction.
In a 1992
study, the critical range separating persons with normal gland function from
those with hypofunction was more precisely identified as unstimulated whole
salivary flow rates between 0.12 and 0.16 mL/min.
If
individualized base rates have been established, then a 50% reduction in flow
should be considered hypofunction.
On average, unstimulated flow rate is 0.3 mL/min
Salivary flow during sleep is nearly zero.
Stimulated flow rate is, at maximum, 7 mL/min.
Stimulated saliva is reported to contribute as much as
80% to 90% of the average daily salivary production.
FACTORS AFFECTING SALIVARY FLOW RATE
Diurnal
variation:
• Protein
concentrations tend to be high in the afternoon.
• Sodium
& chloride concentrations are high in the morning, while potassium is high
in the early afternoon.
• The
calcium concentration increase at night.
Duration of
stimulus:
• If
the salivary glands are stimulated for long than 3 minutes, the concentration
of many components is reduced.
• Chloride concentrations fall during
periods of stimulation.
Hormonal Influences
• Aldosterone: It results in
increased sodium reabsorption in the striated ducts.
• Antidiuretic hormone (ADH):
Stimulates water reabsorption by the
striated duct cells.
• Other
hormones: Thyroxine results in increase salivary secretion
• Local hormones: Bradykinin & its predecessor
kallidin, result in increased salivary secretion.
ANOMALIES
I.Developmental
Aberrant
Salivary Glands
Aplasia and
Hyperplasia
Atresia
II.Obstructive
conditions
Sialolithiasis
Mucocele
Necrotizing
Sialometaplasia
III. Inflammatory
Diseases
Viral- Mumps , H.I.V. Associated
Bacterial - Sialadenitis
IV.Neoplastic
Diseases
Benign
Malignant
V.Degenerative
Conditions
Sjogren’s
Syndrome
Ionizing
Radiation
VI.Xerostomia
XEROSTOMIA
• It
is a condition of reduced or absent salivary flow,leading to the dryness of the
mouth.
• It is not a disease by itself, but a symptom
associated with alterations of salivary function.
• The
principal causes of salivary gland hypofunction & xerostomia
Oral symptoms
1. Dry mouth ( xerostomia )
2. Often thirsty
3.Dysphagia (difficulty with swallowing )
4. Dysphonia (
difficulty with speaking )
5. Dysgeusia ( abnormal taste sensation )
6. Difficulty with
eating dry foods
7. Need to
frequently sip water while eating
8. Difficulty with wearing dentures
9. Often do things to keep mouth moist
10.Burning, tingling,sensation on the tongue.
11.Fissures & sores at corners of lips
Clinical signs
1.
Dryness of lining oral tissues
2.
Loss of glistening of the oral mucosa
3.
Dryness of the oral mucous membranes
4.
Oral mucosa appears thin & pale
5.
Tongue blade/mirror/a gloved finger may adhere
to the soft tissues
6.
Fissuring & lobulation of the dorsum of the
tongue & lips
7.
Angular cheilitis
8.
Candidiasis on tongue & palate
9.
Increased incidence of dental caries
10. Thicker,
more stringy saliva
11. Swelling
of glands
12. Increase
in inflammatory gingival diseases
13. Rapid
tooth destruction associated with cervical or cemental caries
Treatment of salivary hypofunction & xerostomia :
• Systemic
Therapy:
Bromohexine,
anethole, triothiline & pilocarpine Hcl all three should be used under the
care of a specialist & following medical examination.
• Local
Therapy
SALIVARY
SUBSTITUTES
Carboxy methyl cellulose (CMC) based
l Imparts
lubrication and viscosity
l Sorbitol
or xylitol are added to provide surface activity and as a sweetner.
l Have
surface tension greater than natural saliva.
Mucin based
Animal mucins
derived from procine gastric tissues / bovine salivary glands.
Salts are
addeded to mimic the electrolyte content of natural saliva
HYPERSALIVATION
• It
is also known as sialorrhea, ptyalism.
• It
may lead problems in oral motor coordination, including reduced muscle tone
around the mouth & a reduced ability to swallow.
• Causes:
1.
After extensive surgery for oral or
oropharyngeal disorders.
2.
As a result of stomatitis, psychological
factors, & the use of some drugs, Ex: benzodiazepines,captopril
3.
Treatment
i) Drugs –
anticholinergics.
ii) Surgical –
depending on the nature of the anomaly.
DIGNOSTIC APPLICATIONS
The most commonly used laboratory diagnostic procedures
involve the analyses of the cellular and chemical constituents of blood.
There are several ways by which serum constituents
that are not part of the normal salivary constituents (i.e., drugs and
hormones) can reach saliva.
Within
the salivary glands, transfer mechanisms include intracellular and
extracellular routes.
The most common intracellular route is passive
diffusion, although active transport has also been reported.
Ultrafiltration, which occurs through the tight
junctions between the cells, is the most common extracellular route
(Drobitch and Svensson, 1992; Haeckel and Hanecke, 1993; Jusko and Milsap,
1993).
Serum
molecule reaching saliva by diffusion must cross five
barriers: the capillary wall, interstitial space, basal cell membrane of the
acinus cell or duct cell, cytoplasm of the acinus or duct cell, and the luminal
cell membrane (Haeckel and Hanecke, 1996; Fig. 2).
Serum
constituents are also found in whole saliva as a result of GCF outflow. Depending on the degree of inflammation in the
gingiva, GCF is either a serum transudate or, more commonly, an
inflammatory exudate that contains serum constituents.
Advantages
1. saliva
can be collected without breaking the skin or entering the body in any other
way, it has obvious advantages for multiple noninvasive collections and for obtaining
samples from those whom, for cultural reasons or age or because of physical or
mental handicaps, it would be unethical to collect blood samples.
2. saliva levels
are a more accurate reflection of the active hormone in the body, especially
for steroid hormones, which are strongly bound in blood by specific binding
globulins (Read 1989).
3. Saliva
can be collected with devices so that it will be stable at room temperature for
extended periods.
4. Many of
the hazards associated with blood collection do not apply to saliva. There is
no need for sharps, which have the potential for cross contamination among
patients when used improperly and present a danger to health care personnel.
5. Because
of the low concentrations of antigens in saliva, HIV and hepatitis infections
are much less of a danger from saliva than from blood (Major et al. 1991).
6. Because of diurnal and monthly variations,
several steroid hormones need multiple samples collected early in the morning
or late at night or at the same time every day for a month to give meaningful
results (Read 1989). Such collections are often very expensive, inconvenient or
impossible to do with blood.
7. Nonpolar analytes are released into saliva
through the membranes via a mechanism that is not flow dependent. Therefore,
concentrations remain constant relative to blood levels with stimulated and
unstimulated collections (Vining et al. 1983a).
8.
The presence of secretory leukocyte protease inhibitor
(SLPI) may be another factor contributing to the safety of saliva as a
diagnostic specimen.as it expresses antiviral activity against free HIV-1 in a
model
9.
No special equipment is needed for collection of the
fluid.
10. Diagnosis of disease via the analysis
of saliva is potentially valuable for children and older adults, since
collection of the fluid is associated with fewer compliance problems as
compared with the collection of blood.
11. Cost-effective
approach for the screening of large populations.
DISADVANTAGES
1.
samples are not sterile and are subject to bacterial degradation
over time.
2.
Absorbing specimens on cotton may contribute
interfering substances to the extract.
3.
Interpretation of saliva assays is still difficult.
4.
Because blood
concentrations of steroid hormones are several-fold higher than saliva levels,
much has been written about the problems of contamination from bleeding gums.
5.
Polar hormones, such as thyroxine, and the peptide
hormones are subject to variation by flow rate, so reliable levels cannot be
obtained in saliva at this time (Read 1989).
6.
A few kits offer saliva controls with the reagents
Saliva is used for the diagnosis
(1)
Hereditary
Diseases
(2)
Autoimmune Diseases
(3)
Malignancy
(4)
Infectious Diseases
(5)
Drug Monitoring
(6)
The
Monitoring Of Hormone Levels
(7)
Diagnosis Of Oral Disease With Relevance For
Systemic Diseases
Some systemic diseases affect salivary glands directly
or indirectly, and may influence the quantity of saliva that is produced, as
well as the composition of the fluid. These characteristic changes may
contribute to the diagnosis and early detection of these diseases.
Cystic
fibrosis (CF) is a genetically transmitted disease of children and
young adults, which is considered a generalized exocrinopathy. CF is the most
common lethal autosomal-recessive disorder in ,with an incidence of 1 in 2500
and a carrier frequency of 1 in 25-30 of the population.
The gene defect causing CF is present on chromosome 7
and codes for a transmembrane-regulating protein called the cystic fibrosis
transmembrane conductance regulator (CFTR; Riordan et al., 1989;
Dinwiddie, 2000).
A defective electrolyte transport in epithelial cells
and viscous mucus secretions from glands and epithelia characterize this
disorder (Grody, 1999).
The CFTR is also important for plasma membrane
recycling (Bradbury et al., 1992).
The organs mostly affected in CF are:
·
sweat glands, which produce a secretion with elevated
concentrations of sodium and chloride
·
lungs, which develop chronic obstructive pulmonary
disease
·
pancreas,
resulting in pancreatic insufficiency (Davis, 1987).
Since a large
number of identified mutations in the CF gene exist, DNA analysis is not used
for diagnosis of the disease. The diagnosis is derived from the characteristic
clinical signs and symptoms and analysis of elevated sweat chloride values. The
abnormal secretions present in CF caused clinicians to explore the usefulness
of saliva for the diagnosis of the disease.
·
Most studies agree that saliva of CF patients contains
increased calcium levels (Mandel et al., 1967; Blomfield et al.,
1976; Mangos and Donnelly, 1981). Elevated levels of calcium and proteins in
submandibular saliva from CF patients were found, and resulted in a
calcium-protein aggregation which caused turbidity of saliva (Boat et al.,
1974).
·
The elevated calcium and phosphate levels in the
saliva of children diagnosed with CF may explain the fact that these children
demonstrate a higher occurrence of calculus as compared with healthy controls
(Wotman et al., 1973).
·
The submandibular saliva of CF patients was also found
to contain more lipid than saliva of non-affected individuals, and the levels
of neutral lipids, phospholipids, and glycolipids are elevated.
·
Elevations in
electrolytes (sodium, chloride, calcium, and phosphorus), urea and uric acid,
and total protein were observed in the submandibuar saliva of CF patients
(Mandel et al., 1967).
·
Minor salivary glands are also affected.
·
Elevated levels
of sodium and a decrease in flow rate were reported for these glands in CF
patients (Wiesman et al., 1972).
·
However, the parotid saliva of CF patients does not
demonstrate qualitative changes as compared with that of healthy individuals.
·
Amylase and lysozyme activity in the parotid saliva of
CF patients was reported to be similar to that in healthy controls, and
therefore parotid saliva cannot provide diagnostically relevant information for
this disease (Blomfield et al., 1976).
·
Saliva from CF patients was found to contain an
unusual form of epidermal growth factor (EGF). The EGF from these patients
demonstrated poor biological activity compared with EGF from healthy controls.
It was suggested that this EGF anomaly might contribute to the pathology of CF
(Aubert et al., 1990).
·
Further, abnormally elevated levels of prostglandins
E2 (PGE2) were detected in the saliva of CF patients as compared with that of
healthy controls (Rigas et al., 1989).
Coeliac
disease is a congenital disorder of the small intestine that
involves malabsorption of gluten. Gliadin is a major component of gluten.
·
Serum IgA antigliadin antibodies (AGA) are increased
in patients with coeliac disease and dermatitis herpetiformis.
·
Measurement of salivary IgA-AGA has been reported to
be a sensitive and specific method for the screening of coeliac disease, and
for monitoring compliance with the required gluten-free diet (al-Bayaty et
al., 1989; Hakeem et al., 1992).
21-Hydroxylase
deficiency is an inherited disorder of steroidogenesis which
leads to congenital adrenal hyperplasia. In non-classic 21-hydroxylase
deficiency, a partial deficiency of the enzyme is present (Carlson et al.,
1999).
·
Early morning salivary levels of
17-hydroxyprogesterone (17-OHP) were reported to be an excellent screening test
for the diagnosis of non-classic 21- hydroxylase deficiency, since the salivary
levels accurately reflected serum levels of 17-OHP.
AUTOIMMUNE DISEASES—SJÖGREN'S SYNDROME
is an autoimmune exocrinopathy of unknown etiology.
The majority of patients are women
A reduction in lacrimal and salivary secretions is observed,
associated with keratoconjunctivitis sicca and xerostomia. The presence of
these two phenomena leads to a diagnosis of primary SS.
In secondary
SS, a well-defined connective tissue disease (most commonly rheumatoid
arthritis or systemic lupus erythematosus) is present in addition to the
xerostomia and/or the keratoconjunctivitis (Schiødt and Thorn, 1989; Thorn et
al., 1989).
In addition to involvement of the salivary and
lacrimal glands, SS may also affect the skin, lungs, liver, kidneys, thyroid,
and nervous system (Talal, 1992).
The diagnostic criteria for SS are still uncertain,
and a single marker that is associated with all cases does not exist.
The accepted procedure for the diagnosis of the
salivary involvement of SS is a biopsy of the minor salivary glands of the lip.
·
SS is characterized by the presence of a lymphocytic
infiltrate (predominantly CD4+ T-cells) in the salivary gland parenchyma
(Daniels, 1984; Daniels and Fox, 1992).
·
A low resting
flow rate and abnormally low stimulated flow rate of whole saliva are also
indicators of SS (Sreebny and Zhu, 1996a).
·
Serum chemistry can demonstrate polyclonal
hypergammaglobulinemia and elevated levels of rheumatoid factor, antinuclear
antibody, anti-SS-A, and anti-SSB antibody (Atkinson et al., 1990; Fox
and Kang, 1992). The immunologic mechanisms involved in the pathogenesis of the
disease appear also to involve B-cells (the majority of lymphomas associated
with SS are of the B-cell type), salivary epithelial cells, an activated
mononuclear cell infiltrate, cytokines, and adhesion molecules (Fox and
Speight, 1996).
·
In sialochemistry – a consistent finding is increased
concentrations of sodium and chloride. This increase is evident in both whole
and gland specific saliva (Tishler et al., 1997).
·
In addition, elevated levels of IgA, IgG, lactoferrin,
and albumin, and a decreased concentration of phosphate were reported in saliva
of patients with SS (Ben-Aryeh et al., 1981; Stuchell et al.,
1984).
·
Increased salivary concentrations of inflammatory mediators—i.e.,
eicosanoids, PGE2, thromboxane B2, and interleukin-6—have been reported (Tishler
et al., 1996a,b).
·
SS is characterized by autoantibodies to the La and Ro
ribonucleoprotein antigens. These autoantibodies have been shown to target
intracellular proteins which may be involved in the regulation of RNA
polymerase function (Tan, 1989).
·
Autoantibody, especially of the IgA class, can be
synthesized in salivary glands and can be detected in the saliva of SS patients
prior to detection in the serum (Horsfall et al., 1989).
·
Saliva has also been reported to contain IgG
autoantibody, while serum contained primarily IgG and IgM autoantibody (Ben-Chetrit
et al., 1993).
Although variations in these cut-off values between
clinicians may lead to differences in sensitivity and specificity in the
diagnosis of SS, the quantitative evaluation of resting and stimulated saliva
is a simple, non-invasive method of screening for patients who may have SS.
Reduced
salivary flow, although not pathognomonic for SS, is of clinical importance and
can lead to a variety of oral signs and symptoms, such as progressive dental
caries, fungal infections, oral pain, and dysphagia (Daniels and Fox, 1992).
Dentists are normally the first to encounter these
patients. Affected individuals should be referred for a comprehensive
evaluation of the cause for the reduced salivary flow.
MALIGNANCY
Salivary analysis may aid in the early detection of
certain malignant tumors.
p53 is a
tumor suppressor protein which is produced in cells exposed to various types of
DNA-damaging stress.
Inactivation of this suppressor through mutations and gene
deletion is considered a frequent occurrence in the development of human cancer
(Hainaut and Vahakangas, 1997; Tarapore and Fukasawa, 2000).
As a result,
accumulation of inactive p53 protein is observed, which in turn may lead to the
production of antibodies directed against this protein (Bourhis et al., 1996).
These antibodies can be detected in sera of patients
with different types of malignancies (Lubin et al., 1995).
p53 antibody can
also be detected in the saliva of patients diagnosed with oral squamous cell
carcinoma (SCC), and can thus assist in the early detection of, and screening
for, this tumor (Tavassoli et al., 1998).
Defensins are peptides
which possess antimicrobial and cytotoxic properties.
They are found in the azurophil granules of
polymorphonuclear leukocytes (PMNs; Lichtenstein et al., 1986; Lehrer et
al., 1991).
Elevated levels of salivary defensin-1 were found to
be indicative of the presence of oral SCC.
Elevated levels of recognized tumor markers c-erbB-2 (erb) and cancer antigen 15-3 (CA15-3) were
found in the saliva of women diagnosed with breast carcinoma
CA 125 is a
tumor marker for epithelial ovarian cancer. Elevated salivary levels of CA 125
were detected in patients with epithelial ovarian cancer as compared with
patients with benign pelvic masses and healthy controls. A positive correlation
was found between salivary and serum levels of CA 125.
Tumor markers that can be identified in saliva may be potentially
useful for screening for malignant diseases. Salivary diagnosis may be part of
a comprehensive diagnostic panel that will provide improved sensitivity and
specificity in the detection of malignant diseases and will assist in
monitoring the efficacy of treatment. Additional studies are certainly required
to determine which salivary markers can be used for these diagnostic purposes,
and to determine their diagnostic value in comparison with other, more
established, diagnostic tests.
INFECTIOUS DISEASES
DISEASES
Helicobacter
pylori infection is
associated with peptic ulcer disease and chronic gastritis. Infection with this
bacterium stimulates the production of specific IgG antibody. An ELISA test for
the detection of IgG antibody in saliva produced 97% sensitivity and 94%
specificity in detection of the disease. The results also indicated that H.
pylori exists in higher prevalence in saliva than in feces, and the
oral-oral route may be an important means of transmission of this infection in developed
countries (Li et al., 1996).
Evaluation of the secretory immune response in the
saliva of children infected with Shigella
revealed higher titers of anti-lipopolysaccharide and anti-Shiga toxin
antibody in comparison with healthy controls. It was suggested that salivary
levels of these immunoglobulins could be used for monitoring of the immune response
in shigellosis (Schultsz et al., 1992).
Pigeon
breeder's disease (PBD) is an interstitial lung disease induced by exposure
to antigens derived from pigeons. Measurement of salivary IgG against these
antigens may assist in the evaluation of patients with this disease.
The detection of pneumococcal C polysaccharide in
saliva by ELISA may offer a valuable complement to conventional diagnostic methods
for pneumococcal pneumonia.
Detection of this antigen in saliva demonstrated a sensitivity of 55% and
specificity of 97%.
Lyme
disease is caused by the spirochete Borrelia burgdorferi and
is transmitted to humans by blood-feeding ticks. The detection of anti-tick
antibody in saliva has potential as a biologic marker of exposure to tick
bites, which in turn may serve as a screening mechanism for individuals at risk
for Lyme disease (Schwartz et al., 1991).
Specific antibody to Taenia solium larvae in serum demonstrated greater
sensitivity than antibody in saliva for identification of neurocysticercosis
(100% vs. 70.4%, respectively). However, considering the simple and
non-invasive nature of saliva sampling, it was suggested that saliva could be
used in epidemiologic studies of this disease (Feldman et al., 1990).
SALIVARY ENZYMES
Diagnostic
laboratory tests of serum are routinely used in evaluation of many systemic
disorders. In contrast, diagnosis of periodontal disease relies primarily on
clinical (GI, BOP,PD) and radiographic parameters (alveolar bone loss).
A response of an organism to
the periodontal infection includes production of several enzyme families which
are released from stromal, epithelial, inflammatory or bacterial cells.
The analysis of these
enzymes in salivary secretion, as well as in the gingival crevicular fluid, can
contribute to clarification of the pathogenesis and to improvement of making a
prompt diagnosis of the periodontal disease.
Leading roles in this sense
have the enzymes of tissue degradation - elastase, collagenase, gelatinase,
proteinase.
Their activity can be proved
in saliva, within some normal limits, as these enzymes are determined even in
blood of healthy persons. However, if a periodontal tissue becomes sick, or its
cells become damaged, due to edema or destruction of a cellular membrane, i.e.
of a cell as a whole, these intracellular enzymes are increasingly being
released into the gingival crevicular fluid and saliva where their activity can
be measured. Due to this, these enzymes can be biochemical markers of the
functional condition of periodontal tissues
Those particularly relevant
in this group of enzymes are:
1.
aspartate and alanine aminotransferases (AST and ALT),
2.
lactate dehydrogenase (LDH),
3.
gamma-glutamyl transferase
(GGT),
4.
creatine kinase (CK)
5.
alkaline phosphatase (ALP),
6.
acidic phosphatase (ACP).
LDH and AST can help monitor
the progression of the periodontal disease. These enzymes appear to be useful
to test the activity of periodontal disease or to measure the effectiveness of
periodontal therapy
CK, LDH, AST, ALT and GGT are
intracellular enzymes included in metabolic processes of cells and they are
mostly present in cells of soft tissues - indicates the pathological changes
located in soft tissues only, primarily in gingiva what could coincide with the
initial stage of periodontal disease
ALP and ACP are intracellular enzymes
present in most of tissues and organs, particularly in bones. Their increased
activity in saliva is probably the consequence of destructive processes in the
alveolar bone in advanced stages of development of periodontal disease
The activity of
these enzymes in saliva can be of useful for the assessment of efficiency of
changing the therapy in curing periodontal disease (2-4).
Previous studies mainly investigated the
activities of these enzymes in gingival crevicular fluid, which is in a much
closer contact with periodontal tissues and, due to this, it surely much better
reflects the occurrences in them. However, the problem with the gingival
crevicular fluid is in that the technique of collecting is rather complicated
and hardly feasible in practice.
Contrary to the gingival crevicular
fluid, there is plenty of saliva, the procedure of its sampling is much easier
and more bearable for the patient and, the same enzymes as those in the
gingival crevicular fluid can be detected. Becouse of the simple and
non-invasive method of collection, salivary diagnostic tests apper to hold
promise for the future
RESEARCH APPLICATIONS
Saliva already
is used to aid in the diagnosis of dental disease. Examples include caries risk
assessment, periodontal disease genotypes, and identification markers for
periodontal disease, salivary gland disease and dysfunction, and candida
infections.
Salivary
collections are used for diagnostic determinants for viral diseases,
sarcoidosis, tuberculosis, lymphoma, gastric ulcers and cancers, liver
dysfunction, and Sjogren’s syndrome.
Saliva also is
being used to monitor levels of polypeptides, steroids, antibodies, alcohol,
and various other drugs.
Research currently is being conducted to
1. determine
the value of saliva as a diagnostic aid for cancer and preterm labor.
2. regenerative
properties and functions of growth factors found in saliva, such as epidermal
growth factor and transforming growth factor. Evidence suggests that these
growth factors play a role in wound healing and the maintenance of oral and
systemic health.
The multifunctional
roles of salivary components continue to represent a very focused area of
dental research.
·
Can the redundant and synergistic effects of 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 developments in artificial saliva?
Questions such as these are being addressed through
continuing research efforts.
CONCLUSIONS
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 an easily collected, noninvasive source of
information.
Reflective of
the status of health in the body, salivary samples can be analyzed for:
(1) tissue fluid levels of
naturally, therapeutically, and recreationally introduced substances;
(2) emotional status;
(3) hormonal status;
(4) immunologic status;
(5) neurologic status;
(6) nutritional/metabolic influences
REFERENCES
1.
Clinical Periodontology 10th Edition;
Carranza,Newmann.
2.
Shafers textbook of oral pathology. 5th
Edtm
3.
Burkitt’s textboof of oral medicine. 11th
edtn
4.
Periodontology 2000 volume 34: 2004
5.
Tencate’s Oral histology 6th
edition
6.
J. Clinical
Periodontology 2003;30:752-755
7.
J. Clinical
Periodontology 2000,27:453-465
8.
J. Periodontal Research 1990,1983
9.
J. Oral Pathology Medicine 1990.
10. Dentomaxillofac
Radiol 2007;36:59-62. T Bar, A Zagury, D London, R Shacham, and O Nahlieli.
Presentation on this topic can be accessed at -
INTRODUCTION
Saliva is
a most valuable oral fluid that often is taken for granted. It is critical to
the preservation and maintenance of oral health, yet it receives little
attention until quantity or quality is diminished.
Saliva is a complex fluid, produced by the salivary
glands. It is a heterogeneous fluid comprising proteins, electrolytes, small
organic molecules & compounds transported from the blood, constantly bathes
the teeth & oral mucosa.
Saliva is one of the most important fluids in the human
body. Its status in the oral cavity is
at par with that of blood i.e. to remove waste , supply nutrients and
protection of cells.
It acts as a
cleansing solution, an ion reservoir, a lubricant & a buffer.
In addition to its other host - protective properties,
saliva could constitute a first line of defense against free radical-mediated
oxidative stress, since the process of mastication & digestion of ingested
foods promotes a variety of reactions, including lipid peroxidation.
Individuals with a
deficiency of salivary secretion experience difficulty in eating, speaking,
swallowing & become prone to mucosal infections & rampant caries.
Saliva is composed of more than 99% water and less than
1% solids , mostly electrolytes and proteins, the latter giving saliva its
characteristic viscosity. Normally the daily production of whole saliva ranges
from 0.5 to 1.0 litres.
90% of the whole saliva is produced by three paired major
salivary glands
Parotid Gland
Submandibular gland
Sublingual gland
CLASSIFICATION
1.Based on anatomic location
·
Parotid gland
·
Sub mandibular gland
·
Sub lingual gland
·
Accessory glands (labial, lingual, palatal
buccal,glossopalatine and retromolar)
2. Based on size and amount of secretion
·
Major salivary glands
·
Minor salivary glands
3. Based on type
of secretion
·
Serous
·
Mucous
·
Mixed
Parotid glands -
Purely serous
Submandibular-Predominantly
serous, Mixed
Sublingual - Predominantly mucous , Mixed
Labial,Buccal,Lingual{Ant.}-
Predom. Mucous , Mixed
Palatine,Glossopalatine
- Purely mucous.
Posterior part of
the tongue - Purely mucous
Von Ebner’s Glands
- Purely serous
COMPOSITION
Saliva is composed of a variety of electrolytes, including
sodium, potassium, calcium, magnesium, bicarbonate, and phosphates.
Also found in
saliva are immunoglobulins, proteins, enzymes, mucins, and nitrogenous
products, such as urea and ammonia.
These components interact in related function in the
following general areas:
(1) bicarbonates, phosphates, and
urea act to modulate pH and the buffering capacity of saliva; (2) macromolecule
proteins and mucins serve to cleanse, aggregate, and/or attach oral
microorganisms and contribute to dental plaque metabolism;
(3) calcium, phosphate, and proteins
work together as an antisolubility factor and modulate demineralization and remineralization;
(4) immunoglobulins, proteins, and
enzymes provide antibacterial action.
Salivary components, particularly proteins, are
multifunctional (performing more
than 1 function)
redundant (performing similar functions but to
different extents)
amphifunctional (acting both for and against
the host).
Saliva is a very dilute fluid, composed of more than
99% water.
Saliva is not considered an ultrafiltrate of plasma.
Initially,
saliva is isotonic, as it is formed in the acini, but it becomes hypotonic as
it travels through the duct network.
The hypotonicity of unstimulated saliva
·
allows the taste buds to perceive different tastes
without being masked by normal plasma sodium levels.
·
Hypotonicity, especially during low flow periods, also
allows for expansion and hydration of mucin glycoproteins, which protectively
blanket tissues of the mouth.
·
Lower levels of glucose, bicarbonate, and urea in
unstimulated saliva augment the hypotonic environment to enhance taste.
The normal pH of saliva is 6 to 7, meaning that it is
slightly acidic. The pH in salivary flow can range from 5.3 (low flow) to 7.8
(peak flow).
Major salivary glands contribute most of the secretion
volume and electrolyte content to saliva, whereas minor salivary glands
contribute little secretion volume and most of the blood-group substances.
FUNCTIONS
PROPERTIES OF SALIVA
• Consistency
: Slightly cloudy
• Reaction
: Usually slightly acidic
• PH
: 5-8
• Specific
gravity : 1.0024 – 1.0061
• Freezing
point :0.07 – 0.34 degree Celsius
• Osmotic
pressure : ( 700-1000m osmol/litre
)
TIME
OF ORIGIN
STAGES OF DEVELOPMENT
• STAGE
I-Bud formation:
1.
Induction of proliferation of oral epithelium by
underlying mesenchyme.
2.
Individual salivary glands arise as a
proliferation of oral epithelial cells, forming a focal thickening that grows
into the underlying ectomesenchyme.
3.
These long epithelial cords undergo repeated
dichotomous branching, called, “Branching morphogenesis”, that produces successive
generations of buds & a hierarchial ramification of the gland & the mesenchymal cells condense
around the bud.
·
STAGE II:Formation and growth of
epithelial cord
·
STAGE III: Initiation of
branching in terminal parts of epithelial cord and continuation of glandular
differentiation.
·
STAGEIV: Dichotomous branching of
epithelial cord and lobule formation.
1.
The
development of a lumen within the branched generally occurs first in the distal
end of the main cord & finally in the central portion of the main cord.
2.
The lumen
form within the ducts before they develop within the terminal buds.
3.
Some
studies have suggested that lumen formation may involve the apoptosis of
centrally located cells in the cords.
·
STAGE V:Canalization of presumptive
ducts.
1.
Following
development of the lumen in the terminal buds, the epithelium consists of two
layers of cells.
a)
The cells
of the inner layer eventually differentiate into the secretory cells of the
mature gland, mucous / serous.
b)
Some cells
of the outer layer form the contractile myoepithelial cells that are present
around the secretory end pieces & intercalated ducts.
2.
As the
epithelial parenchymal components increase in size & number, the associated
mesenchyme ( connective tissue ) is diminished, although a thin layer of connective tissue remains, surrounding each
secretory end piece & duct of the adult gland.
·
STAGE
VI:
Cytodifferentiation.
Cells of ® Terminal tubule cell ® Proacinar cells®Acinar cells
Bulb region ¯
Intercalated duct
cell
• Septa ( Thicker partitions of the
connective tissue ) which are continuous with the connective tissue capsule
surrounding the gland parenchyma into lobes & lobules & carry the blood
vessels & nerves that supply the parenchymal components & the excretoryducts.
The cells of the secretory end pieces & ducts attain
maturity during the last 2 months of gestation.
The glands continue to grow post natally with the volume
proportion of acinar tissue increasing & the volume proportions of ducts
connective tissue & vascular elements decreasing upto 2 years of age.
MORPHOLOGIC CHARACTERISTICS OF MAJOR SALIVARY GLANDS
Parotid gland
Ø Largest
of all the salivary glands
Ø Purely
serous gland that produce thin , watery amylase rich saliva
Ø Superficial
portion lies in front of external ear & deeper portion lies behind the
ramus of mandible
Ø Stensen's Duct (Parotid Papilla) opens out adjacent to maxillary second molar.
Submandibular Gland
Ø
Second
largest salivary gland
Ø
Mixed gland
Ø
Located
in the posterior part of floor of mouth,adjacent to medial aspect of
mandible & wrapping around the posterior border of mylohyoid muscle.
Ø
Wharton's
Duct opens beneath the
tongue at sub-lingual caruncle lateral to the lingual frenum
Sublingual Gland
Ø Smallest
salivary gland
Ø Mixed
gland but mucous secretory cells predominate.
Ø Located
in anterior part of floor of mouth between the mucosa and mylohyoid muscle
Ø Opens
through series of small ducts (ducts of rivinus) opening along the sub-lingual
fold & often through a larger duct (bartholin’s duct)
The minor salivary glands:
Ø
Estimated numbers is 600-1000.
Ø
Exist as small,discrete,aggregates of secretory
tissue present in the submucosa through out most of the oral cavity, except the
gingival & anterior part of the hard palate.
Ø
Predominantly mucous glands,except for Von Ebners glands(purely serous)
Ø
Here intercalated & striated ducts are
poorly developed.
VASCULAR SUPPLY
PAROTID GLAND
Arterial: Ext.Carotid Artery and its branches
Venous: Ext.Jugular
Vein
Lymphatic: Parotid Nodes® Upper deep cervical nodes
SUBMANDIBULAR GLAND
Arterial: Facial
Artery , Lingual Artery
Venous:
Common Facial Vein /Lingual Vein
Lymphatic: Submandibular Lymph
nodes
SUBLINGUAL GLAND
Arterial: Lingual
and Submental Arteries
Venous: Lingual
Vein
INFLUENCE OF BLOOD SUPPLY ON SALIVARY
SECRETION
q
Extensive
blood supply is required for rapid salivary secretion.
q
Salivation
indirectly dilates blood vessels providing increased nutrition.
q
Large increase in blood flow accompanies
salivary secretion.
INNERVATION
Parasympathetic innervation to major salivary glands
} Otic
ganglion suplies the parotid gland.
} Submandibular
ganglion supplies the other major glands.
Sympathetic innervation
Promotes the
flow of saliva and stimulates muscle contraction at salivary ducts
REGULATION OF SALIVARY SECRETION
The secretion of saliva is controlled by a salivary
center composed of nuclei in the medulla.
Three types of
triggers, or stimuli, for this production are
·
mechanical (the act of chewing),
·
gustatory (with acid the most stimulating trigger and
sweet the least stimulating),
·
olfactory (a surprisingly poor stimulus).
Other factors affecting secretion include
·
psychic factors such as pain,
·
certain types of medication
·
various local or systemic diseases affecting the
glands themselves.
Salivary glands
are innervated by both sympathetic and parasympathetic nerve fibers.
·
When sympathetic innervations dominate, the secretions
contain more protein from acinar cells,
·
parasympathetic
innervations produce a more watery secretion.
SALIVARY GLAND STRUCTURE
Composed of
parenchymal elements supported by connective tissue
The types of
cells found in the salivary glands are duct system cells, acinar cells, and
myoepithelial cells.
•
Intercalated duct : main duct
connecting acinar secretions to rest of the gland, not involved in
modification of electrolytes
•
Striated duct: electrolyte regulation in resorbing sodium
•
Excretory duct: continuing sodium resorption and secreting
potassium
•
Inter cellular canaliculi : These are the extensions of the lumen of the end piece between adjacent
secretory cells that serve to increase the terminal surface area available for
secretion.
•
Secretory end pieces:
branched ducts, terminating in spherical or tubular secretory end
pieces/ acini.
Secretory cells: There are two types of secretory cells.
1.serous cells
2.mucous cells
These two cells
differ in structure, as seen in classical histologic & electron microscopic
analyses, & in the types of macromolecular components that they produce
& secrete.
1.SEROUS
CELLS:
a) These are
spherical, consisting of 8-12 cells surrounding a central lumen.
b) Cells are pyramidal with a broad base adjacent
to the connective tissue stroma & a narrow apex forming part of the lumen
of the end piece.
c) The lumen
usually has finger like extensions located between adjacent cells called inter
cellular canaliculi.
d) Spherical
nuclei are located basally, occasionally binucleated cells are seen.
e) Secretory
granules in which macromolecular components of saliva are stored, are present
in the apical cytoplasm.
f) These cells are joined by intercellular
junctions.
a.Zonula occludens( tight junction)
b.Zonula adherens(Adhering junction)
c.Macula adherens(desmosome)
Tight junctions
exhibit a selective permeability, allowing the passage of certain ions &
water.
These cells are
attached to the basal lamina & the underlying connective tissue by
hemidesmosomes.
2.MUCOUS
ACINI:
a) These have a
tubular configuration.
b) When cut in
cross section, these tubules appear as round profiles with mucous cells
surrounding a central lumen of larger size than that of serous end pieces
c) Mucous end
pieces in the major salivary glands & some minor salivary glands have
serous cells associated with them in the form of a demilune or cresent covering
the mucous cells at the end of the tubule.\
d) The most
prominent feature of the mucous cell is the accumulation in the apical
cytoplasm of large amounts of secretory product (mucus), which compresses the
nucleus & endoplasmic reticulum & golgi complex against the basal cell
membrane.]
e) Unlike serous
cells, however, mucous cells lack intercellular canaliculi, except for those
covered by demilune cells.
3.MYOEPITHELIAL CELLS:
a)These are
basket shaped cells, contractile in nature & are associated with the
secretory end pieces & intercalated ducts of the salivary glands.
b) They are
located between the basal lamina & the secretory/duct cells & are
joined to the cells by desmosomes.
c) These are
similar to the smooth muscle cells but are derived from the epithelium.
d) Contraction of
the myoepithelial cells is due to actin & myosin, which helps to provide
support for the end pieces during active secretion of saliva.
e) These may help
to expel the primary saliva from the endpiece into the duct system.
f) They provide
signals to the acinar secretory cells that are necessary for maintaining cell
polarity & the structural organization of the secretory end piece.
g) They produce a
no. of proteins that have tumour suppressor activity, such as proteinase
inhibitors ( ex : tissue inhibitor of metalloproteinases ) &
antiangiogenesis factors
h) provide a
barrier against invasive epithelial neoplasms.
FORMATION OF SALIVA
The salivary glands are composed of specialized
epithelial cells, and their structure can be divided into two specific regions:
the acinar and ductal regions.
The acinar region is where fluid is generated and most
of the protein synthesis and secretion takes place. Amino acids enter the
acinar cells by means of active transport, and after intracellular protein
synthesis, the majority of proteins are stored in storage granules that are
released in response to secretory stimulation (Young and Van Lennep, 1978; Castle,
1993).
Three models have been described for acinar fluid secretion
1. active
transport of anions into the lumen and passage of water according to the osmotic
gradient from the interstitial fluid into the salivary lumen (Turner et al.,
1993).
2. The
initial fluid is isotonic in nature and is derived from the local vasculature.
3. While
acinar cells are water-permeable, ductal cells are not.
Ductal cells actively absorb most of the Na+ and Cl-
ions from the primary salivary secretion and secrete small amounts of K+ and
HCO3 - and some proteins.
The primary salivary secretion is thus modified, and
the final salivary secretion as it enters the oral cavity is hypotonic (Baum, 1993).
The autonomic nervous system (sympathetic and
parasympathetic) controls the salivary secretion. The signaling mechanism involves
the binding of neurotransmitter (primarily acetylcholine and norepinephrine) to
plasma membrane receptors and signal transduction via guanine
nucleotide-binding regulatory proteins (G-proteins) and activation of intracellular
calcium signaling mechanisms (for reviews, see Baum, 1987, 1993; Ambudkar,
2000).
SALIVARY GLAND SECRETIONS
Saliva can be considered as gland-specific saliva and whole
saliva.
Gland-specific
saliva can be collected directly from individual salivary
glands: parotid, submandibular, sublingual, and minor salivary glands. Useful
for the detection of gland-specific pathology, i.e., infection and
obstruction.
Whole
saliva (mixed saliva) is a mixture of oral fluids and includes secretions
from both the major and minor salivary glands, in addition to several
constituents of non-salivary origin, such as gingival crevicular fluid (GCF),
expectorated bronchial and nasal secretions, serum and blood derivatives from
oral wounds, bacteria and bacterial products, viruses and fungi, desquamated
epithelial cells, other cellular components, and food debris. Used when salivary analysis is used for the
evaluation of systemic disorders.
Saliva can be collected with or without stimulation.
Stimulated
saliva is collected by masticatory action (i.e., from
a subject chewing on paraffin) or by gustatory stimulation (i.e.,
application of citric acid on the subject's tongue; Mandel, 1993).
Unstimulated
saliva is collected without exogenous gustatory,
masticatory, or mechanical stimulation.
COLLECTION OF SALIVA
•
Non invasive, non painful techniques exist to
collect whole saliva, as well as saliva from the individual major & minor
salivary glands .
•
Whole
saliva is easily obtained & is in most case a good indicator of whole mouth
dryness.
•
Diseases
of salivary gland can often be diagnosed from the secretions obtained directly.
•
The quantification of salivary output is
referred to as sialometry.
University of Southern California School of Dentistry
guidelines
• Unstimulated
whole saliva collection always should precede stimulated whole saliva
collection.
• The
patient is advised to refrain from intake of any food or beverage (water
exempted) one hour before the test session.
• Smoking, chewing gum and intake of coffee also
are prohibited during this hour.
• The
subject is advised to rinse his or her mouth several times with distilled water
and then to relax for five minutes.
• Keep
his mouth slightly open and allow saliva to drain into the tube.
• Should
last for five minutes
Collection Of
Stimulated Saliva
• Paraffin
method (Masticatory stimulus ): Ask the patient to hold a piece of paraffin
in his or her mouth until it becomes soft ( about 30 seconds) & then to
swallow the saliva which has collect in his mouth. Now the patient is asked to
chew the piece of wax in his usual manner of chewing for exactly 2 minutes
& then to expectorate the accumulated saliva into the receiving vessel .The
volume of saliva is read off the vessel & flow is expressed as ml/min.
• Citric
Acid method ( Gustatory Stimulus ): A 2% solution of citric acid is swabbed
on to the laterodorsal surface of the tongue every 30 seconds for a period of 2
min & then saliva is expectorated into the receiving vessel. As in the
paraffin method, the whole procedure is repeated twice more, for a total time
of 6 mins. As before, the flow is expressed as ml/min.
SALIVARY FLOW RATE
There is great variability in individual salivary flow
rates.
The accepted range of normal flow for unstimulated
saliva is anything above 0.1 mL/min.
For stimulated saliva, the minimum volume for the
accepted norm increases to 0.2 mL/min.
Any unstimulated flow rate below 0.1 mL/min is
considered hypofunction.
In a 1992
study, the critical range separating persons with normal gland function from
those with hypofunction was more precisely identified as unstimulated whole
salivary flow rates between 0.12 and 0.16 mL/min.
If
individualized base rates have been established, then a 50% reduction in flow
should be considered hypofunction.
On average, unstimulated flow rate is 0.3 mL/min
Salivary flow during sleep is nearly zero.
Stimulated flow rate is, at maximum, 7 mL/min.
Stimulated saliva is reported to contribute as much as
80% to 90% of the average daily salivary production.
FACTORS AFFECTING SALIVARY FLOW RATE
Diurnal
variation:
• Protein
concentrations tend to be high in the afternoon.
• Sodium
& chloride concentrations are high in the morning, while potassium is high
in the early afternoon.
• The
calcium concentration increase at night.
Duration of
stimulus:
• If
the salivary glands are stimulated for long than 3 minutes, the concentration
of many components is reduced.
• Chloride concentrations fall during
periods of stimulation.
Hormonal Influences
• Aldosterone: It results in
increased sodium reabsorption in the striated ducts.
• Antidiuretic hormone (ADH):
Stimulates water reabsorption by the
striated duct cells.
• Other
hormones: Thyroxine results in increase salivary secretion
• Local hormones: Bradykinin & its predecessor
kallidin, result in increased salivary secretion.
ANOMALIES
I.Developmental
Aberrant
Salivary Glands
Aplasia and
Hyperplasia
Atresia
II.Obstructive
conditions
Sialolithiasis
Mucocele
Necrotizing
Sialometaplasia
III. Inflammatory
Diseases
Viral- Mumps , H.I.V. Associated
Bacterial - Sialadenitis
IV.Neoplastic
Diseases
Benign
Malignant
V.Degenerative
Conditions
Sjogren’s
Syndrome
Ionizing
Radiation
VI.Xerostomia
XEROSTOMIA
• It
is a condition of reduced or absent salivary flow,leading to the dryness of the
mouth.
• It is not a disease by itself, but a symptom
associated with alterations of salivary function.
• The
principal causes of salivary gland hypofunction & xerostomia
Oral symptoms
1. Dry mouth ( xerostomia )
2. Often thirsty
3.Dysphagia (difficulty with swallowing )
4. Dysphonia (
difficulty with speaking )
5. Dysgeusia ( abnormal taste sensation )
6. Difficulty with
eating dry foods
7. Need to
frequently sip water while eating
8. Difficulty with wearing dentures
9. Often do things to keep mouth moist
10.Burning, tingling,sensation on the tongue.
11.Fissures & sores at corners of lips
Clinical signs
1.
Dryness of lining oral tissues
2.
Loss of glistening of the oral mucosa
3.
Dryness of the oral mucous membranes
4.
Oral mucosa appears thin & pale
5.
Tongue blade/mirror/a gloved finger may adhere
to the soft tissues
6.
Fissuring & lobulation of the dorsum of the
tongue & lips
7.
Angular cheilitis
8.
Candidiasis on tongue & palate
9.
Increased incidence of dental caries
10. Thicker,
more stringy saliva
11. Swelling
of glands
12. Increase
in inflammatory gingival diseases
13. Rapid
tooth destruction associated with cervical or cemental caries
Treatment of salivary hypofunction & xerostomia :
• Systemic
Therapy:
Bromohexine,
anethole, triothiline & pilocarpine Hcl all three should be used under the
care of a specialist & following medical examination.
• Local
Therapy
SALIVARY
SUBSTITUTES
Carboxy methyl cellulose (CMC) based
l Imparts
lubrication and viscosity
l Sorbitol
or xylitol are added to provide surface activity and as a sweetner.
l Have
surface tension greater than natural saliva.
Mucin based
Animal mucins
derived from procine gastric tissues / bovine salivary glands.
Salts are
addeded to mimic the electrolyte content of natural saliva
HYPERSALIVATION
• It
is also known as sialorrhea, ptyalism.
• It
may lead problems in oral motor coordination, including reduced muscle tone
around the mouth & a reduced ability to swallow.
• Causes:
1.
After extensive surgery for oral or
oropharyngeal disorders.
2.
As a result of stomatitis, psychological
factors, & the use of some drugs, Ex: benzodiazepines,captopril
3.
Treatment
i) Drugs –
anticholinergics.
ii) Surgical –
depending on the nature of the anomaly.
DIGNOSTIC APPLICATIONS
The most commonly used laboratory diagnostic procedures
involve the analyses of the cellular and chemical constituents of blood.
There are several ways by which serum constituents
that are not part of the normal salivary constituents (i.e., drugs and
hormones) can reach saliva.
Within
the salivary glands, transfer mechanisms include intracellular and
extracellular routes.
The most common intracellular route is passive
diffusion, although active transport has also been reported.
Ultrafiltration, which occurs through the tight
junctions between the cells, is the most common extracellular route
(Drobitch and Svensson, 1992; Haeckel and Hanecke, 1993; Jusko and Milsap,
1993).
Serum
molecule reaching saliva by diffusion must cross five
barriers: the capillary wall, interstitial space, basal cell membrane of the
acinus cell or duct cell, cytoplasm of the acinus or duct cell, and the luminal
cell membrane (Haeckel and Hanecke, 1996; Fig. 2).
Serum
constituents are also found in whole saliva as a result of GCF outflow. Depending on the degree of inflammation in the
gingiva, GCF is either a serum transudate or, more commonly, an
inflammatory exudate that contains serum constituents.
Advantages
1. saliva
can be collected without breaking the skin or entering the body in any other
way, it has obvious advantages for multiple noninvasive collections and for obtaining
samples from those whom, for cultural reasons or age or because of physical or
mental handicaps, it would be unethical to collect blood samples.
2. saliva levels
are a more accurate reflection of the active hormone in the body, especially
for steroid hormones, which are strongly bound in blood by specific binding
globulins (Read 1989).
3. Saliva
can be collected with devices so that it will be stable at room temperature for
extended periods.
4. Many of
the hazards associated with blood collection do not apply to saliva. There is
no need for sharps, which have the potential for cross contamination among
patients when used improperly and present a danger to health care personnel.
5. Because
of the low concentrations of antigens in saliva, HIV and hepatitis infections
are much less of a danger from saliva than from blood (Major et al. 1991).
6. Because of diurnal and monthly variations,
several steroid hormones need multiple samples collected early in the morning
or late at night or at the same time every day for a month to give meaningful
results (Read 1989). Such collections are often very expensive, inconvenient or
impossible to do with blood.
7. Nonpolar analytes are released into saliva
through the membranes via a mechanism that is not flow dependent. Therefore,
concentrations remain constant relative to blood levels with stimulated and
unstimulated collections (Vining et al. 1983a).
8.
The presence of secretory leukocyte protease inhibitor
(SLPI) may be another factor contributing to the safety of saliva as a
diagnostic specimen.as it expresses antiviral activity against free HIV-1 in a
model
9.
No special equipment is needed for collection of the
fluid.
10. Diagnosis of disease via the analysis
of saliva is potentially valuable for children and older adults, since
collection of the fluid is associated with fewer compliance problems as
compared with the collection of blood.
11. Cost-effective
approach for the screening of large populations.
DISADVANTAGES
1.
samples are not sterile and are subject to bacterial degradation
over time.
2.
Absorbing specimens on cotton may contribute
interfering substances to the extract.
3.
Interpretation of saliva assays is still difficult.
4.
Because blood
concentrations of steroid hormones are several-fold higher than saliva levels,
much has been written about the problems of contamination from bleeding gums.
5.
Polar hormones, such as thyroxine, and the peptide
hormones are subject to variation by flow rate, so reliable levels cannot be
obtained in saliva at this time (Read 1989).
6.
A few kits offer saliva controls with the reagents
Saliva is used for the diagnosis
(1)
Hereditary
Diseases
(2)
Autoimmune Diseases
(3)
Malignancy
(4)
Infectious Diseases
(5)
Drug Monitoring
(6)
The
Monitoring Of Hormone Levels
(7)
Diagnosis Of Oral Disease With Relevance For
Systemic Diseases
Some systemic diseases affect salivary glands directly
or indirectly, and may influence the quantity of saliva that is produced, as
well as the composition of the fluid. These characteristic changes may
contribute to the diagnosis and early detection of these diseases.
Cystic
fibrosis (CF) is a genetically transmitted disease of children and
young adults, which is considered a generalized exocrinopathy. CF is the most
common lethal autosomal-recessive disorder in ,with an incidence of 1 in 2500
and a carrier frequency of 1 in 25-30 of the population.
The gene defect causing CF is present on chromosome 7
and codes for a transmembrane-regulating protein called the cystic fibrosis
transmembrane conductance regulator (CFTR; Riordan et al., 1989;
Dinwiddie, 2000).
A defective electrolyte transport in epithelial cells
and viscous mucus secretions from glands and epithelia characterize this
disorder (Grody, 1999).
The CFTR is also important for plasma membrane
recycling (Bradbury et al., 1992).
The organs mostly affected in CF are:
·
sweat glands, which produce a secretion with elevated
concentrations of sodium and chloride
·
lungs, which develop chronic obstructive pulmonary
disease
·
pancreas,
resulting in pancreatic insufficiency (Davis, 1987).
Since a large
number of identified mutations in the CF gene exist, DNA analysis is not used
for diagnosis of the disease. The diagnosis is derived from the characteristic
clinical signs and symptoms and analysis of elevated sweat chloride values. The
abnormal secretions present in CF caused clinicians to explore the usefulness
of saliva for the diagnosis of the disease.
·
Most studies agree that saliva of CF patients contains
increased calcium levels (Mandel et al., 1967; Blomfield et al.,
1976; Mangos and Donnelly, 1981). Elevated levels of calcium and proteins in
submandibular saliva from CF patients were found, and resulted in a
calcium-protein aggregation which caused turbidity of saliva (Boat et al.,
1974).
·
The elevated calcium and phosphate levels in the
saliva of children diagnosed with CF may explain the fact that these children
demonstrate a higher occurrence of calculus as compared with healthy controls
(Wotman et al., 1973).
·
The submandibular saliva of CF patients was also found
to contain more lipid than saliva of non-affected individuals, and the levels
of neutral lipids, phospholipids, and glycolipids are elevated.
·
Elevations in
electrolytes (sodium, chloride, calcium, and phosphorus), urea and uric acid,
and total protein were observed in the submandibuar saliva of CF patients
(Mandel et al., 1967).
·
Minor salivary glands are also affected.
·
Elevated levels
of sodium and a decrease in flow rate were reported for these glands in CF
patients (Wiesman et al., 1972).
·
However, the parotid saliva of CF patients does not
demonstrate qualitative changes as compared with that of healthy individuals.
·
Amylase and lysozyme activity in the parotid saliva of
CF patients was reported to be similar to that in healthy controls, and
therefore parotid saliva cannot provide diagnostically relevant information for
this disease (Blomfield et al., 1976).
·
Saliva from CF patients was found to contain an
unusual form of epidermal growth factor (EGF). The EGF from these patients
demonstrated poor biological activity compared with EGF from healthy controls.
It was suggested that this EGF anomaly might contribute to the pathology of CF
(Aubert et al., 1990).
·
Further, abnormally elevated levels of prostglandins
E2 (PGE2) were detected in the saliva of CF patients as compared with that of
healthy controls (Rigas et al., 1989).
Coeliac
disease is a congenital disorder of the small intestine that
involves malabsorption of gluten. Gliadin is a major component of gluten.
·
Serum IgA antigliadin antibodies (AGA) are increased
in patients with coeliac disease and dermatitis herpetiformis.
·
Measurement of salivary IgA-AGA has been reported to
be a sensitive and specific method for the screening of coeliac disease, and
for monitoring compliance with the required gluten-free diet (al-Bayaty et
al., 1989; Hakeem et al., 1992).
21-Hydroxylase
deficiency is an inherited disorder of steroidogenesis which
leads to congenital adrenal hyperplasia. In non-classic 21-hydroxylase
deficiency, a partial deficiency of the enzyme is present (Carlson et al.,
1999).
·
Early morning salivary levels of
17-hydroxyprogesterone (17-OHP) were reported to be an excellent screening test
for the diagnosis of non-classic 21- hydroxylase deficiency, since the salivary
levels accurately reflected serum levels of 17-OHP.
AUTOIMMUNE DISEASES—SJÖGREN'S SYNDROME
is an autoimmune exocrinopathy of unknown etiology.
The majority of patients are women
A reduction in lacrimal and salivary secretions is observed,
associated with keratoconjunctivitis sicca and xerostomia. The presence of
these two phenomena leads to a diagnosis of primary SS.
In secondary
SS, a well-defined connective tissue disease (most commonly rheumatoid
arthritis or systemic lupus erythematosus) is present in addition to the
xerostomia and/or the keratoconjunctivitis (Schiødt and Thorn, 1989; Thorn et
al., 1989).
In addition to involvement of the salivary and
lacrimal glands, SS may also affect the skin, lungs, liver, kidneys, thyroid,
and nervous system (Talal, 1992).
The diagnostic criteria for SS are still uncertain,
and a single marker that is associated with all cases does not exist.
The accepted procedure for the diagnosis of the
salivary involvement of SS is a biopsy of the minor salivary glands of the lip.
·
SS is characterized by the presence of a lymphocytic
infiltrate (predominantly CD4+ T-cells) in the salivary gland parenchyma
(Daniels, 1984; Daniels and Fox, 1992).
·
A low resting
flow rate and abnormally low stimulated flow rate of whole saliva are also
indicators of SS (Sreebny and Zhu, 1996a).
·
Serum chemistry can demonstrate polyclonal
hypergammaglobulinemia and elevated levels of rheumatoid factor, antinuclear
antibody, anti-SS-A, and anti-SSB antibody (Atkinson et al., 1990; Fox
and Kang, 1992). The immunologic mechanisms involved in the pathogenesis of the
disease appear also to involve B-cells (the majority of lymphomas associated
with SS are of the B-cell type), salivary epithelial cells, an activated
mononuclear cell infiltrate, cytokines, and adhesion molecules (Fox and
Speight, 1996).
·
In sialochemistry – a consistent finding is increased
concentrations of sodium and chloride. This increase is evident in both whole
and gland specific saliva (Tishler et al., 1997).
·
In addition, elevated levels of IgA, IgG, lactoferrin,
and albumin, and a decreased concentration of phosphate were reported in saliva
of patients with SS (Ben-Aryeh et al., 1981; Stuchell et al.,
1984).
·
Increased salivary concentrations of inflammatory mediators—i.e.,
eicosanoids, PGE2, thromboxane B2, and interleukin-6—have been reported (Tishler
et al., 1996a,b).
·
SS is characterized by autoantibodies to the La and Ro
ribonucleoprotein antigens. These autoantibodies have been shown to target
intracellular proteins which may be involved in the regulation of RNA
polymerase function (Tan, 1989).
·
Autoantibody, especially of the IgA class, can be
synthesized in salivary glands and can be detected in the saliva of SS patients
prior to detection in the serum (Horsfall et al., 1989).
·
Saliva has also been reported to contain IgG
autoantibody, while serum contained primarily IgG and IgM autoantibody (Ben-Chetrit
et al., 1993).
Although variations in these cut-off values between
clinicians may lead to differences in sensitivity and specificity in the
diagnosis of SS, the quantitative evaluation of resting and stimulated saliva
is a simple, non-invasive method of screening for patients who may have SS.
Reduced
salivary flow, although not pathognomonic for SS, is of clinical importance and
can lead to a variety of oral signs and symptoms, such as progressive dental
caries, fungal infections, oral pain, and dysphagia (Daniels and Fox, 1992).
Dentists are normally the first to encounter these
patients. Affected individuals should be referred for a comprehensive
evaluation of the cause for the reduced salivary flow.
MALIGNANCY
Salivary analysis may aid in the early detection of
certain malignant tumors.
p53 is a
tumor suppressor protein which is produced in cells exposed to various types of
DNA-damaging stress.
Inactivation of this suppressor through mutations and gene
deletion is considered a frequent occurrence in the development of human cancer
(Hainaut and Vahakangas, 1997; Tarapore and Fukasawa, 2000).
As a result,
accumulation of inactive p53 protein is observed, which in turn may lead to the
production of antibodies directed against this protein (Bourhis et al., 1996).
These antibodies can be detected in sera of patients
with different types of malignancies (Lubin et al., 1995).
p53 antibody can
also be detected in the saliva of patients diagnosed with oral squamous cell
carcinoma (SCC), and can thus assist in the early detection of, and screening
for, this tumor (Tavassoli et al., 1998).
Defensins are peptides
which possess antimicrobial and cytotoxic properties.
They are found in the azurophil granules of
polymorphonuclear leukocytes (PMNs; Lichtenstein et al., 1986; Lehrer et
al., 1991).
Elevated levels of salivary defensin-1 were found to
be indicative of the presence of oral SCC.
Elevated levels of recognized tumor markers c-erbB-2 (erb) and cancer antigen 15-3 (CA15-3) were
found in the saliva of women diagnosed with breast carcinoma
CA 125 is a
tumor marker for epithelial ovarian cancer. Elevated salivary levels of CA 125
were detected in patients with epithelial ovarian cancer as compared with
patients with benign pelvic masses and healthy controls. A positive correlation
was found between salivary and serum levels of CA 125.
Tumor markers that can be identified in saliva may be potentially
useful for screening for malignant diseases. Salivary diagnosis may be part of
a comprehensive diagnostic panel that will provide improved sensitivity and
specificity in the detection of malignant diseases and will assist in
monitoring the efficacy of treatment. Additional studies are certainly required
to determine which salivary markers can be used for these diagnostic purposes,
and to determine their diagnostic value in comparison with other, more
established, diagnostic tests.
INFECTIOUS DISEASES
DISEASES
Helicobacter
pylori infection is
associated with peptic ulcer disease and chronic gastritis. Infection with this
bacterium stimulates the production of specific IgG antibody. An ELISA test for
the detection of IgG antibody in saliva produced 97% sensitivity and 94%
specificity in detection of the disease. The results also indicated that H.
pylori exists in higher prevalence in saliva than in feces, and the
oral-oral route may be an important means of transmission of this infection in developed
countries (Li et al., 1996).
Evaluation of the secretory immune response in the
saliva of children infected with Shigella
revealed higher titers of anti-lipopolysaccharide and anti-Shiga toxin
antibody in comparison with healthy controls. It was suggested that salivary
levels of these immunoglobulins could be used for monitoring of the immune response
in shigellosis (Schultsz et al., 1992).
Pigeon
breeder's disease (PBD) is an interstitial lung disease induced by exposure
to antigens derived from pigeons. Measurement of salivary IgG against these
antigens may assist in the evaluation of patients with this disease.
The detection of pneumococcal C polysaccharide in
saliva by ELISA may offer a valuable complement to conventional diagnostic methods
for pneumococcal pneumonia.
Detection of this antigen in saliva demonstrated a sensitivity of 55% and
specificity of 97%.
Lyme
disease is caused by the spirochete Borrelia burgdorferi and
is transmitted to humans by blood-feeding ticks. The detection of anti-tick
antibody in saliva has potential as a biologic marker of exposure to tick
bites, which in turn may serve as a screening mechanism for individuals at risk
for Lyme disease (Schwartz et al., 1991).
Specific antibody to Taenia solium larvae in serum demonstrated greater
sensitivity than antibody in saliva for identification of neurocysticercosis
(100% vs. 70.4%, respectively). However, considering the simple and
non-invasive nature of saliva sampling, it was suggested that saliva could be
used in epidemiologic studies of this disease (Feldman et al., 1990).
SALIVARY ENZYMES
Diagnostic
laboratory tests of serum are routinely used in evaluation of many systemic
disorders. In contrast, diagnosis of periodontal disease relies primarily on
clinical (GI, BOP,PD) and radiographic parameters (alveolar bone loss).
A response of an organism to
the periodontal infection includes production of several enzyme families which
are released from stromal, epithelial, inflammatory or bacterial cells.
The analysis of these
enzymes in salivary secretion, as well as in the gingival crevicular fluid, can
contribute to clarification of the pathogenesis and to improvement of making a
prompt diagnosis of the periodontal disease.
Leading roles in this sense
have the enzymes of tissue degradation - elastase, collagenase, gelatinase,
proteinase.
Their activity can be proved
in saliva, within some normal limits, as these enzymes are determined even in
blood of healthy persons. However, if a periodontal tissue becomes sick, or its
cells become damaged, due to edema or destruction of a cellular membrane, i.e.
of a cell as a whole, these intracellular enzymes are increasingly being
released into the gingival crevicular fluid and saliva where their activity can
be measured. Due to this, these enzymes can be biochemical markers of the
functional condition of periodontal tissues
Those particularly relevant
in this group of enzymes are:
1.
aspartate and alanine aminotransferases (AST and ALT),
2.
lactate dehydrogenase (LDH),
3.
gamma-glutamyl transferase
(GGT),
4.
creatine kinase (CK)
5.
alkaline phosphatase (ALP),
6.
acidic phosphatase (ACP).
LDH and AST can help monitor
the progression of the periodontal disease. These enzymes appear to be useful
to test the activity of periodontal disease or to measure the effectiveness of
periodontal therapy
CK, LDH, AST, ALT and GGT are
intracellular enzymes included in metabolic processes of cells and they are
mostly present in cells of soft tissues - indicates the pathological changes
located in soft tissues only, primarily in gingiva what could coincide with the
initial stage of periodontal disease
ALP and ACP are intracellular enzymes
present in most of tissues and organs, particularly in bones. Their increased
activity in saliva is probably the consequence of destructive processes in the
alveolar bone in advanced stages of development of periodontal disease
The activity of
these enzymes in saliva can be of useful for the assessment of efficiency of
changing the therapy in curing periodontal disease (2-4).
Previous studies mainly investigated the
activities of these enzymes in gingival crevicular fluid, which is in a much
closer contact with periodontal tissues and, due to this, it surely much better
reflects the occurrences in them. However, the problem with the gingival
crevicular fluid is in that the technique of collecting is rather complicated
and hardly feasible in practice.
Contrary to the gingival crevicular
fluid, there is plenty of saliva, the procedure of its sampling is much easier
and more bearable for the patient and, the same enzymes as those in the
gingival crevicular fluid can be detected. Becouse of the simple and
non-invasive method of collection, salivary diagnostic tests apper to hold
promise for the future
RESEARCH APPLICATIONS
Saliva already
is used to aid in the diagnosis of dental disease. Examples include caries risk
assessment, periodontal disease genotypes, and identification markers for
periodontal disease, salivary gland disease and dysfunction, and candida
infections.
Salivary
collections are used for diagnostic determinants for viral diseases,
sarcoidosis, tuberculosis, lymphoma, gastric ulcers and cancers, liver
dysfunction, and Sjogren’s syndrome.
Saliva also is
being used to monitor levels of polypeptides, steroids, antibodies, alcohol,
and various other drugs.
Research currently is being conducted to
1. determine
the value of saliva as a diagnostic aid for cancer and preterm labor.
2. regenerative
properties and functions of growth factors found in saliva, such as epidermal
growth factor and transforming growth factor. Evidence suggests that these
growth factors play a role in wound healing and the maintenance of oral and
systemic health.
The multifunctional
roles of salivary components continue to represent a very focused area of
dental research.
·
Can the redundant and synergistic effects of 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 developments in artificial saliva?
Questions such as these are being addressed through
continuing research efforts.
CONCLUSIONS
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 an easily collected, noninvasive source of
information.
Reflective of
the status of health in the body, salivary samples can be analyzed for:
(1) tissue fluid levels of
naturally, therapeutically, and recreationally introduced substances;
(2) emotional status;
(3) hormonal status;
(4) immunologic status;
(5) neurologic status;
(6) nutritional/metabolic influences
REFERENCES
1.
Clinical Periodontology 10th Edition;
Carranza,Newmann.
2.
Shafers textbook of oral pathology. 5th
Edtm
3.
Burkitt’s textboof of oral medicine. 11th
edtn
4.
Periodontology 2000 volume 34: 2004
5.
Tencate’s Oral histology 6th
edition
6.
J. Clinical
Periodontology 2003;30:752-755
7.
J. Clinical
Periodontology 2000,27:453-465
8.
J. Periodontal Research 1990,1983
9.
J. Oral Pathology Medicine 1990.
10. Dentomaxillofac
Radiol 2007;36:59-62. T Bar, A Zagury, D London, R Shacham, and O Nahlieli.
This Presentation on this topic can be accessed from