1. Dental Biochemistry 2 – (Lec. 10,11)
Biochemistry of Teeth,
Saliva and Dental Caries
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2. Saliva
• Is the biological fluid, which bathes the oral cavity.
• It is a complex fluid produced by a number of
specialized glands which discharge into the oral
cavity.
• Saliva contains electrolytes and proteins.
• Electrolytes are minerals in your blood and other
body fluids that carry an electric charge.
• The total volume of saliva produced each day in
adults is 500 to 1500 ml.
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3. Functions of Saliva
i. Antibacterial and antifungal action
ii. Buffering
iii. Digestion
iv. Mineralization
v. Lubrication.
vi. Many salivary components do multiple jobs. For
example, amylase in addition to being an enzyme
also inhibits precipitation of calcium salts.
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4. Composition of Saliva
• The parotid glands produce serous secretions only,
devoid of mucin.
• On the other hand, the submandibular and
sublingual glands secrete both serous and mucinous
secretions.
• The viscosity of the submandibular saliva usually
decreases with increasing flow rate.
• Salivary secretion is stimulated by smell and taste.
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5. Characteristics of mixed saliva
• Volume 500-1500 ml I day
• Rate of flow 0.1--0.25 mil min
• pH 5.6-7.2 (mean 6.5)
• Water content 97-99.5%
• Total protein 01--0.6 g/dl
• Mucin 0.27 g I dl
• Glucose 10-20 mg/dl
• Potassium 10-40 mMoI/L
• Sodium 2-50 mMoI/L
• Calcium 1-2.5 mMoI/L
• Magnesium 0.2--0.6 mMoI/L
• Phosphate 2-22 mMoI/L
• Chloride 5-50 mMollL
• Total lipid 20 mg/dl
• Cholesterol 7.5 mg/dl
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6. Inorganic Components
Saliva contains the usual electrolytes of
the body fluids, the principal ions being
sodium. potassium, chloride and
bicarbonate.
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7. Organic Components
• i. Major carbohydrate in saliva is glucose (10-20
mg/dl)
• ii. Almost all the organic compounds of plasma.
such as hormones, immunoglobulins and enzymes
may be detected in saliva in trace amounts.
• Iii. The total protein concentration in saliva is very
little and is less than 1% of that In plasma.
Important proteins of saliva include, mucin,
statherins, histatins, lysozyme, proline rich proteins
(PRPs), carbonic anhydrase, lingual lipase, amylase,
peroxidase lactoferrin and immunoglobulin A (lgA).
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8. Mucins
• They constitute the major proteins of the saliva.
• The salivary mucins exist in two forms; MG1 and
MG2. Both are glycoproteins.
• They contain negatively charged groups, such as
sialic acid and sulfate.
• They are hydrophilic and trap water resulting in
high elasticity.
• The oligosaccharide residues bind to bacterial
proteins preventing them from adhering to soft
tissue and enamel.
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9. Functions of mucin
Tissue coating
• Protective coating about hard and soft tissues
• Primary role in formation of acquired pellicle
• Concentrates antimicrobial molecules at mucosal
interface
Lubrication
• Align themselves with direction of flow increases
lubricating qualities
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10. Salivary Enzymes
• The main enzymes present in saliva are the
amylase, lingual lipase, carbonic anhydrase and
peroxidases.
• Saliva supplies enzymes for digestion.
• These enzymes and other proteins including
saliva specific glycoproteins, are synthesized by
the acinar cells.
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11. Amylase
• The major salivary enzyme is alpha amylase.
• The amylase acts on carbohydrates. It cleaves the alpha-1,4-
glycosidic bonds of starch. The products are small quantities
of maltose (disaccharide) and smaller sized polysaccharides.
• The optimum pH of salivary amylase is 6. However, its action
is short lived as the food passes into stomach and the
enzyme becomes Inactive at the highly acidic pH of the
gastric lumen.
• The parotid gland secretes most of the amylase.
• When there is any obstruction to the salivary ducts or
inflammation of the glands (as in mumps), the salivary
amylase passes into the blood and elevates the level of
serum amylase.
• Amylase also shows weak antibacterial properties as well as
buffering property. 11

12. Other Enzymes
• i. Lingual lipase acts on triglycerides and is
important in the digestion of milk fat in infants.
• Ii. Carbonic anhydrase is responsible for the
buffering action of saliva.
• iii. Peroxidases assist in the bactericidal function.
• iv. Lysozyme in saliva has antimicrobial action. The
bactericidal effect is by breaking down the
muramic acid present in bacterial cell walls.
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13. Other Proteins
• I. Immunoglobulin A (lgA) is the antibodies present
in body secretions. It may be effective against
cariogenic bacteria. IgA levels are found to be low
in some persons with dental caries
• ii. Lactoferrin chelates the iron.
• iii. Saliva also contains a group of histidine rich
proteins with antifungal activity.
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14. • iv. Statherins are proteins that keep the
supersaturated calcium phosphate in the ductal
saliva from crystallizing.
• The supersaturated calcium phosphate is necessary
for the maintenance of enamel integrity.
• Statherins bind calcium and prevent precipitation of
calcium phosphate. So the probability of formation
of dental calculus is reduced.
• The statherins also help in lubrication.
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15. v. The Proline Rich Protein (PRP) contains a large
number of proline residues (40% or more).
• They also reduce precipitation of calcium
phosphate.
• PRPs also help in the formation of the enamel
pellicle.
• This reduces the bacterial attacks
• Slows down the loss of calcium and phosphate
ions from the teeth.
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16. COMPOSITION OF TEETH
• During the formation of teeth, there is a close
association of inorganic (mineral) crystal material,
and organic fibrous (polymer) structures, both
components playing a structural role in the tooth.
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17. Inorganic Components
• i. The inorganic calcium is deposited along with
phosphate as apatite, which is the major form of
calcium in all the tooth tissues.
• A small proportion of other crystalline forms of
calcium phosphate may also exist in teeth.
• Amorphous (noncrystalline) calcium phosphate
may be found in the dentin.
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18. • ii. The phosphate ions constitute the major
component of the ions present in the crystal.
• iii. The arrangement of phosphate ions results in
octahedral channels running through the crystal
structure.
• iv. Two-thirds of these channels are occupied by
calcium ions.
• The remaining third of the channels are occupied
by negative fluoride ions. This is called
fluoroapatite.
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19. Trace Elements
• In human enamel, trace elements such as iron,
zinc, copper, and manganese are found.
• Iron and zinc accumulate near the surface of
the tooth, i.e. in the outer layers of enamel.
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20. Organic Components
• Collagen
• It is the major protein component of calcifying
tissues like bone, dentin and cementum.
• Each polypeptide chain of collagen has about 1000
amino acid residues.
• The structural proteins and apatite of teeth need
to be synthesized in an integrated way.
• In teeth the collagen fibrils are suited to the roles
of supporting three-dimensional stress, and of
orienting and supporting apatite crystals.
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21. Other Proteins in Teeth
• i. In addition to collagen, the extracellular matrix
also contains glycoproteins (GP) and
glycosaminoglycans (GAG).
• These proteins are associated with the dentin and
basal plate.
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22. Proteins of Dentin
• The extracellular matrix proteins of bone and dentin
are similar consisting of type 1 collagen, acidic glycoproteins
and proteoglycans.
• Collagen forms the lattice for mineralization, but non-
collagen proteins control initiation and growth of crystals.
• Three major proteins found specifically in dentin but
absent in bone are:
• i. Dentin phosphoryn
• ii. Dentin matrix protein
• Iii. Dentin sialoprotein
• These proteins play an important role in control of
mineralization.
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23. Proteins of Enamel
• i. Amelogenin is a low molecular weight
extracellular matrix protein.
• It constitutes about 90% of all enamel protein.
• It has hydrophobic residues on the outside.
Function
• The 27 amino acid portion of amelogenin functions
as a calcium channel.
• Phosphorylation of a serine residue of the protein
opens the calcium channel, Through which calcium
ions zoom through and funneled to the
mineralization front.
• It also influences the development of cementum.23

24. • ii. Mutation of amelogenin gene leads to
amelogenesis imperfecta which is an inherited
condition characterized by abnormal enamel
formation in quantity, growth, maturation and
crystallization in amelogenesis imperfecta.
• The genes are present on X and Y chromosomes
designated AMELX and AMELY.
• iii. The other proteins found in enamel are
ameloblastin, enamelin and tuftelin.
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25. 25

26. Mineralization
• I. Mineralization is a process by which inorganic
calcium and phosphate are deposited on the
organic matrix.
• ii. Osteoblasts synthesize and secrete organic
matrix, which is then mineralized.
• iii. Osteoclasts are Involved in bone resorption.
• iv. Alkaline phosphatase is the key enzyme in the
process of mineralization. The enzyme liberates
phosphate from substrates, so that Ionic
concentration (of calcium x phosphate) is increased
to supersaturation level, leading to deposition of
apatite.
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27. DENTAL CARIES
• Caries is a Latin term, meaning "decay".
• There is local destruction of tooth tissues with
demineralization.
• Alternative terms are dental cavities or tooth decay.
• In the pits and fissures of premolar and molar
teeth, bacterial fermentation of residual food leads
to acid production.
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28. Microbiological Organisms Cause
Dental Caries
• The development of caries lesion requires the
presence of the bacteria Streptococcus mutans.
• This is generally seen in the oral mucosa and in
dental plaque.
• When there is a decrease in saliva flow, the pH of
the plaque drops, allowing the acid tolerant bacteria
like S. mutans to proliferate.
• S. mutans forms dextran and causes a sticky plaque,
trapping bacteria, calcium and phosphate ions.
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29. Sucrose and Caries
• ii. Sucrose is a low-molecular-weight disaccharide
that can be rapidly metabolized by the plaque flora.
• iii. Sucrose fermentation produces lactic acid with
consequent drop in the pH, to 5.0 or lower, at the
Point of interface between plaque and enamel.
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30. Other Causes of Dental Caries
• Even though sugars and poor oral hygiene are the
major causes of caries.
• In adults chewing of tobacco and exposure to lead,
cadmium (metals that can replace calcium) are
implicated in the genesis of caries.
• Iodine is found to be able to penetrate enamel,
dental pulp and periodontal tissues.
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31. Prevention of Caries
• i. Ideally, oral hygiene is the best way to prevent
caries. This consists of proper brushing at least
twice a day and regular dental examination and
cleaning, every 6 months.
• ii. However, frequent eating also increases the
chances of developing caries, since it keeps the
plaque pH low for longer periods. Hence. the
Importance of proper cleaning and removing food
debris after consumption of food.
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32. • iii. High molecular weight starch and proteins are
not well-utilized by the bacteria. So, milk, fresh
fruits and vegetables are not cariogenic.
• iv. Dietary factors that protect teeth against caries
are fluoride and sugar free salivary stimulants.
• v. An important concept about treatment of caries
is that the destroyed tooth will not regenerate.
The aim of treatment is thus to prevent caries or
to arrest the progression of caries.
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33. Fluoride is Useful to Prevent Caries
• i. Intake of 2·4 microgram fluoride per day leads to
decrease in the incidence of dental caries.
• Several possible mechanisms are postulated,
which include:
a. Effect on hard tissues to modulate mineralization,
demineralization and re-mineralization.
b. Effect of cariogenic bacteria by altering their
metabolism.
c. Effect on soft tissues to modify the development of
teeth.
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34. Fluorosis is More Dangerous Than
Caries
• i. Fluoride level more than 2 ppm (2 mg/l) will
cause chronic intestinal upset, gastroenteritis, loss
of appetite and loss of weight.
• ii. Levels more than 5 ppm cause mottling of
enamel, stratification and discoloration of teeth.
• iii. A level more than 20 ppm is toxic, leading to
alternate areas of osteoporosis and osteosclerosis,
with brittle bones. This is called fluorosis.
• iv. Ingested fluoride accumulates in bones. It is a
cumulative toxin. 34

35. • v. In fluorosis, blood concentration of fluoride
Increases to 50 microgram/100 ml; whereas normal
value is 4 microgram/100 ml.
• vi. Fluorosis is characterized by joint defects. Due to
increased breakdown of bone matrix, excretion of
hydroxyproline in urine is enhanced.
• N. B.
• Fluorinated toothpaste contains 3,000 ppm of
fluoride. Even ordinary toothpaste contains fluoride
about 700 ppm.
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36. Prevention of Fluorosis
• Provide fluoride free water,
• Supplementation of vitamin C
• Avoiding fluoride containing
toothpaste.
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