Transcript Biochemistry of tooth tissues and saliva: biological role, physical-chemical

Biochemistry of tooth tissues and saliva:
biological role, physical-chemical
properties and biochemical content.
Regulation and pathology of saliva
formation, significance in the appearance
of dental diseases.
Teeth
The role is to masticate (chew) food
 Humans have two sets of teeth

– Deciduous (baby or milk) teeth
– 20 teeth are fully formed by age two

Permanent teeth
– Replace deciduous teeth beginning between
the ages of 6 to 12
– A full set is 32 teeth, but some people do not
have wisdom teeth
Tooth is a complex system of
specialized tissues
Teeth contain tooth
enamel and dentin
•Dentin contains
collagen and is similar
in composition to bone
A . TOOTH TISSUES
1. TOOTH ENAMEL, is the hardest part of the tooth
Enamel acts as a protective tissue that covers the
exposed part of a tooth, the crown.
2. DENTIN , is the tissue that forms the mainl mass of
a tooth. It supports the enamel and absorbs the
pressure of eating.
3. DENTAL PULP, a soft connective tissue containing
nerves and blood vessels, that nourish the tooth.
4. CEMENTUM, covers the dentine outside of the root
(under the gum line) and it is attached to the bone
of the jaw with little elastic fibers
Dentin

Dentin is a mineralized
connective tissue with
an organic matrix of
collagenous proteins.
• dentin contain
exclusively genetic Type
I collagen
• The chain are high in
glycine (Gly), proline
(Pro) and hydroxyproline
(Hyp) content.

Composed of mineralized calcium phosphate
(specifically, the calcium phosphate phase
called hydroxyapatite (HAP) 
Ca10(PO4)6(OH)2) within a matrix of collagen
fibrils

The HAP of teeth is not compositionally pure

HAP is a ‘living mineral’ that is continually
grown, dissolved & remodeled in response to
signals of internal (e.g., pregnancy) and
external (e.g., gravity, exercise) origin
– it’s composition can actually be better
represented as
– (Ca, Sr, Mg, Na, H2O)10(PO4, HPO4,
CO3P2O7)6(OH, F, Cl, H2O)2
Apatites of tooth tissues

Ca10(PO4)6(OH)2

Ca8H2(PO4)6 · 5H2O

Ca10(PO4)6CO3 or
Ca10(PO4)5CO3(OH)2

Ca10(PO4)6Cl

SrCa9(PO4)6(OH)2

Ca10(PO4)6F2
Hydroxyappatite

Enamel is 95% HAP

Enamel gains mechanical
strength by interweaving HAP
crystals

Enamel initially starts with a high
protein content, but these are
removed and the voids backfilled
with HAP as the tooth matures
B. PERIODONTAL TISSUES
5. GUMS, the tough pinkcolored skin that covers the
bone of the jaw and
supports the tooth along
with the alveolar bone.
HEALTHY GINGIVA
CONTAINS MANY
FIBROBLASTS AND A FEW
INFLAMMATORY CELLS
SUCH AS MACROPHAGES
,NEUTROPHILS, PLASMA
CELLS AND LYMPHOCYTES.
6. PERIODONTAL LIGAMENT, the
tissue between the cementum and the
alveolar bone. It consists of tough little
elastic fibers that keep the tooth
attached to the jaw.
7. ALVEOLAR BONE, the bone of the
jaw that keeps the tooth in its place, it
feeds and protects it.


Enamel is the hardest and most highly mineralized
substance of the body, and with dentin, cementum,
and dental pulp is one of the four major tissues which
make up the tooth.
Ninety-six percent of enamel consists of mineral,
with water and organic material composing the rest.

The formation of dentin - dentinogenesis. The porous,
yellow-hued material is made up of

70% inorganic materials,
20% organic materials,
10% water.


Cementum
Cementum is a specialized bony substance covering
the root of a tooth.
 45% inorganic material (mainly hydroxyapatite),
 33% organic material (mainly collagen)
 22% water.
Cementum is excreted by cementoblasts within the root
of the tooth and is thickest at the root apex.


Pulp
The dental pulp is the part in the center of a tooth
made up of living soft tissue and cells called
odontoblasts. Those include: Fibroblasts,
Granulocites, Histiosites etc. It's commonly called
'the nerve', although it contains many other
structures which are not nerves.
Biochemical composition of teeth tissues
Compounds
Water
pulp
dentin
enamel
cementum
g per 100 g tissue
30 - 40
13
2,5
3,2
Organic
compounds
40
20
4
25
Inorganic
compounds
20 - 30
69
96
70
Ca
g per 100 g of ashes
30
35
36
35,5
Mg
0,8
1,2
0,5
0,9
Na
0,2
1,2
0,2
1,1
K
0,1
0,1
0,3
0,1
P
17,0
17,4
17,3
17,1
F
0,02
0,02
0,02
0,02
citrate
-
1,0
0,3
-
Organic components
Soluble proteins:
Albumins, globulins
Enzymes:
 Alkaline phosphatase
 Acidic phosphatase
 Glycoproteins
No soluble proteins:
 Collagen
 Enamelin
Carbohydrates



Glycogen
Glycosaminoglycans (GAG,
mucopolysaccharides) are longchain compounds made up of
hundreds repeating
disaccharide units. One of the
sugars in each disaccharide unit
is a hexosamine (glycosamine).
Many proteoglycans contain a
core protein which links them
to the cellular membrane.
Proteoglycans

Hyaluronic acid is an
extremely long and
rigid
glycosaminoglycan

Chondroitin 6
sulphate
Dental plaque
Plaque is a biofilm consisting of large amounts of
various bacteria which forms on teeth. If not
removed regularly, it can lead to dental cavities
(caries) or periodontal problems (such as
gingivitis).
Given time, plaque can mineralize along the
gingiva, forming tartar. The microorganisms that
form the biofilm are almost entirely bacteria
(mainly streptococcus and anaerobes). Certain
bacteria in the mouth in the absence of oxygen
produce lactic acid, which dissolves the calcium
and phosphorus in the enamel. This process demineralisation, leads to tooth destruction.
Scurvy

Scurvy - dietary
deficiency in
vitamin C, leading
to abnormal
collagen.
(hemorrhages, loose of
teeth, gums swell and
bleed easily)
Dental caries
Dental caries, also described as "tooth decay" or "dental cavities",
is an infectious disease which damages the structures of teeth.
Tooth decay is caused by certain
types of acid-producing bacteria
which cause the most damage in
the presence of fermentable
carbohydrates such as sucrose,
fructose, and glucose. The
resulting acidic levels in the
mouth affect teeth because a
tooth's special mineral content
causes it to be sensitive to low
pH
Teeth demineralisation:
Са10 (РО4)6(ОН)2 + 2Н+ → Са9Н2 (РО4)6(ОН)2 + Са2+
Conversion of GAP into ftorapatite:
Са10 (РО4)6(ОН)2 + 2F- → Са10 (РО4)6F2 + 2(ОН)-
Excess of F- couses demineralisation
Са10 (РО4)6(ОН)2 + 20F- → 10CаF2 + 6РО4 3- + 2(ОН)-
ph 6,4 - 7,8 assists in mineralization
Са2+/ Р for mineralization in saliva is 1,67
Mg2+, Mn2+, Zn2+, Cu2+, Si2+ increase
mineralization
ph<6,2 leads to the demineralization
ORAL ENVIRONMENT
CARIES
A progressively destructive, infectious disease resulting
in:



Demineralization of enamel / cementum
Bacterial penetration to pulp
Formation of macroscopic activity
Sound enamel
plaque
acid prod
mineral
loss
saliva
acid neutralization
Lesions
mineral gain
(fluoride)
Cavity
Caries promotion
dietary carbohydrate
reduced salivary flow
cariogenic bacteria
Caries reduction
increased salivary flow
reduced plaque
fluoride
ORAL ENVIRONMENT
SALIVA
A complex fluid secreted by salivary glands containing
water, mucin, proteins, salts and enzymes.
Functions:
–
–
–
–
–
aids in digestion
lubricates both hard and soft tissues
buffers cariogenic acids
forms the pellicle
provides minerals for repairing enamel / cementum
(remineralization)
– delivers antimicrobial agents (immunoglobulins, enzymes,
etc.)
Saliva neutralises the acids which cause
the pH of the tooth surface to rise
above the critical pH. This causes
'remineralisation', the return of the
dissolved minerals to the enamel.
In the presence of plaque, saliva is unable
to penetrate through the plaque to
neutralize the acid produced by the
bacteria.
Salivary glands
SALIVA
•Mixture of mucus
and serous fluids
•Helps to form a
food bolus
•Contains salivary
amylase to begin
starch digestion
•Dissolves
chemicals so they
can be tasted

Saliva is secreted to the mouth by
three major paired salivary glands
(submamandibular, parotid, and
sublingual glands) and by numerous
minor mucous glands, at a rate of
approximately 0.025 ml.min-1.
65 % from the submandibular,
 23 % from the parotid,
 8 % from the minor mucous,
 4 % from the sublingual.

Secretions of Salivary Glands

Parotid glands
– clear
– water, serous fluid
– rich in amylase

Sublingual glands
– primarily mucus
– most viscous

Submandibular glands
– primarily serous fluid
– some mucus
The most important small salivary glands are:
 lingual glands
 minor sulblingual glands close to the larger major
sublingual glands
 labial glands on the inner surface of the lips
 palatine glands
 tonsillar glands
 buccal glands


The labial, sublingual, mlnor lingual and buccal glands
are composed predominantly of mucous cells, but some
serous cells may be present.
The palatine and lateral lingual glands are entirely
mucous secreting
Digestion
 The digestive functions of saliva
include moistening food, and
helping to create a food bolus, so
it can be swallowed easily.
 Saliva contains the enzyme
Amylase that breaks some
starches down into maltose and
dextrin.
 Salivary glands also secrete
enzyme to start fat digestion.
This is useful for infants to
digest the fat in milk.
Pellicle deposits
In addition to this, saliva is responsible
for depositing salivary pellicle that
covers the entirety of the tooth
surfaces.
 This pellicle
play a role in plaque formation, it may also
act as a protective barrier between
acids and the tooth surface

Disinfectants
 Saliva contained in the mouth has
natural disinfectants.
 Human saliva contains such
antibacterial agents as secretory IgA,
 lactoferrin, and lactoperoxidase.
Stimulation
The production of saliva is stimulated both
by the sympathetic nervous system and
the parasympathetic.
 The saliva stimulated by sympathetic
innervation is thicker, and saliva stimulated
parasympathetically is more watery.

Daily salivary output

There has been some disagreement
regarding the daily salivary output in a
healthy individual. Today, it is believed
that the average person produces
approximately 700mL of saliva per day,
which is much less than was once
thought.

Saliva is characteristically a colorless
dilute fluid, with a density ranging from
18 to 35. Its pH is usually around 6.64,
and varies depending on the
concentration of CO2 in the blood.

The total concentration of inorganic and
organic constituents is generally low
when compared to serum.
– There are four major components of saliva:
 mucus that serves as a lubricant,
 amylase, an enzyme that initiates the
digestion of starch,
 lingual lipase, an enzyme that begins the
digestion of fat, and
 a slightly alkaline electrolyte solution that
moistens food.
– Human saliva is always hypotonic to plasma. Na+ and
Cl- concentrations are less than that of plasma; but K+
and HCO3- concentrations are higher in saliva than in
plasma. Amylase and mucus also increase in
concentration after stimulation.
Saliva Composition
Produced in salivary glands, saliva is 98% water, but it
contains many important substances, including
electrolytes, mucus, antibacterial compounds and various
enzymes.
 Water
 Electrolytes:
– 2-21 mmol/L sodium (lower than blood plasma)
– 10-36 mmol/L potassium (higher than plasma)
– 1.2-2.8 mmol/L calcium
– 0.08-0.5 mmol/L magnesium
– 5-40 mmol/L chloride (lower than plasma)
– 25 mmol/L bicarbonate (higher than plasma)
- 1.4-39 mmol/L phosphate


Mucus. Mucus in saliva mainly
consists of
mucopolysaccharides and
glycoproteins;

Antibacterial compounds
(thiocyanate, hydrogen
peroxide, and secretory
immunoglobulin A)

In its secretory form, IgA is the
main immunoglobulin found in
mucous secretions, including
tears, saliva
ENZYMES

There are three major
enzymes found in saliva.
– α-amylase. Amylase starts the
digestion of starch and lipase
fat before the food is even
swallowed. It has a pH optima
of 7.4.
– lysozyme. Lysozyme acts to
lyse bacteria.
– lingual lipase. Lingual lipase has
a pH optimum ~4.0 so it is not
activated till entering an acidic
environment.
Enzymes

– Minor enzymes include salivary acid phosphatases
A+B,
– N-acetylmuramyl-L-alanine amidase, NAD(P)H
dehydrogenase-quinone,
– salivary lactoperoxidase,
– superoxide dismutase,
– glutathione transferase,
– aldehyde dehydrogenase,
– glucose-6-phosphate isomerase,
– tissue kallikrein.
Cells: Possibly as much as 8 million human and 500
million bacterial cells per mL. The presence of
bacterial products (small organic acids, amines, and
mercaptans) causes saliva to sometimes exhibit foul
odor.
Biochemical composition of human saliva in relation to
other mucosal fluids

Histatins are polypeptides which possess exceptional
anti-fungal and anti-bacterial activities, but are
nevertheless present only in saliva.

Proline-rich proteins (PRPs) are members of a closely
related family, of which the acidic PRPs are found
solely in saliva.

Mucins are a group of glycoproteins that contribute to
the visco-elastic character of the mucosal secretions.
Mucins have distinct tissue distributions and amino
acid sequences. Other salivary proteins are present in
one or more mucosal secretions.
Lysozyme is an example of a component
belonging to an ancient self-defense system,
whereas secretory immunoglobulin A (sIgA)
is the secreted part of a adaptive immune system.

Cystatins are closely related proteins which belong to a
multigene family.

Alpha-Amylase plays a specific role in digestion, but is
nevertheless present in several body fluids.

Kallikrein and albumin are components of blood plasma. But
whereas albumin diffuses into the different mucosal secretions,
kallikrein is secreted specifically by the mucosal glands.

the pH changes
from being slightly
acidic (at rest) to
basic (pH 8) at
ultimate
stimulation. This
increase in
alkalinity is due to
the increase of
HCO3- in the saliva
Salivary Dysfunction

Major types of disorders affect the salivary glands:
one that results in salivary gland malfunction,
whereby not enough saliva is produced, and one that
results in salivary gland swelling.

When the flow of saliva is insufficient or almost
nonexistent.This condition - dry mouth (xerostomia).
Hypothyroid states, diabetes mellitus, and HIV and
hepatitis C infection have all been associated with
xerostomia.

The loss of saliva can have multiple deleterious
consequences, including a constant sense of dryness
(xerostomia), increased tooth decay, fungal infections
and oral burning (Candidiasis), decreased or altered
taste, difficulty speaking and swallowing, and
recurrent salivary gland infections.
Too much or too little saliva can affect oral
health and quality of life.

Hyposalivation leads to dental decay, oral
yeast infections, taste problems, bad breath,
difficulty speaking and swallowing, and
recurrent salivary glands infections. The loss
of saliva is not associated with the
development of periodontal disease

Hypersalivation can cause social problems and
may be a sign of an underlying medical
problem (stomatitis, pulpitis, parodontitis
etc).
ORAL ENVIRONMENT
PLAQUE
Soft sticky, invisible film constantly forming in your
mouth. Covers teeth and gums.



Oral mucosa cells
Saliva
Bacteria
Can be removed by brushing and flossing.
Gram + cocci
(healthy mouth)
Gram + rods
Formation / progression influenced by:



Diet
Host immune system
Oral environment
Gram – anaerobes
(gingivitis)
Taste Disorders
Loss of taste
 Persistent unusual or unexpected tastes
 Perversions of taste (for example, when
something sweet tastes salty)


Evaluation includes medical history review,
head, neck and oral examination, diagnostic
imaging, salivary function assessment, and
testing of ability to taste and smell.

Salivary Gland Swelling: Salivary gland
swelling can occur when one of the ducts that
carry saliva from the salivary gland to the
mouth is blocked. Pain may occur, especially
during eating.

The most common cause of blockage is a
stone. Salivary gland stones are most common
in adults; 25% of those with stones have more
than one. A stone can form from salts
contained in the saliva. Blockage makes saliva
back up inside the duct, causing the salivary
gland to swell. A blocked duct and gland filled
with stagnant saliva may become infected
with bacteria.
Candidiasis
Mumps





Mumps is an infection caused by a virus and
can cause:
Fever
Headache
Swelling and tenderness of glands in one or
both sides of the neck (called parotitis)
Running nose and eyes, sore throat and ears
particularly in young children.
Occasionally serious complications of mumps
infection can occur. These less common, but
more serious symptoms include:
 A meningitis
 Ear infections which can lead to hearing
impairment.
 Swelling and tenderness of the testicles in
adult men (orchitis), and inflammation of the
ovaries (oophoritis) in women, though it is
very rare for these to cause serious
complications such as infertility.
 Pancreatitis inflammation of the pancreas.

Mumps, certain bacterial infections,
and other diseases (such as AIDS,
Sjögren's syndrome, diabetes
mellitus, and sarcoidosis) may be
accompanied by swelling of the major
salivary glands. Swelling also can
result from cancerous or noncancerous
tumors in the salivary glands.

An injury to the lower lip may harm
any of the minor salivary glands found
there and block the flow of saliva.