Prof. d-r R. Kabaktchieva- 2014

In 1890 W. D. Miller, an American dentist teaching
in Germany, published his chemico-parasitic
theory of caries

Miller believed that extraction of the lime salts from
the teeth was a result of bacterial acidogenesis
It was the first step in dental decay
 Miller's
work failed to identify
dental plaque as the source of the
bacteria and the bacterial acids
G.
V. Black, described the
gelatinous microbial plaque
as the source of the acids.

Dental caries is a multifactorial disease
process, often represented by the
interlocking circles
Influence of MO, carbohydrates
over time
For caries to
develop,
4 conditions
must occur
simultaneously:
(1) There must be a
susceptible tooth and host;
(2) Cariogenic
microorganisms must be
present in a sufficient
quantity;
(3) There must be frequent
excessive consumption of
refined carbohydrates;
(4) This process must occur
over a sufficiently long
period of time.

When a tooth covered with cariogenic bacteria
is exposed to a suitable substrate, such as a
refined carbohydrate,

=
the bacteria
produce acid.
If these conditions persist over a sufficiently long
period of time
an incipient lesion
develops

The incipient lesion is the initial stage of
tooth decay that has not penetrated the
outer surface of the tooth.

The lesion looks like a white spot on the
enamel.
caries
incipient lesion
Physical and Microscopic Features of
Incipient Caries

The incipient lesion in her earliest stage, is
characterized by
histological changes of
the enamel

These changes include demineralization
which represents the loss of
calcium and phosphate and
other ions from the enamel
Physical and Microscopic Features of Incipient Caries

The second stage includes the progress of
demineralization
toward the dentinoenamel
junction (DEJ),
then continues into the
dentin.

The final phase of caries development is the
development of the open or visible lesion
that is actually a really cavitation
We can also say overt, or frank, lesion
 The
early identification of the incipient
lesion is extremely important,
 because it is during this stage that the
carious process
can be arrested or reversed!!!
 The
incipient lesion is macroscopically visible
on the tooth surface by the appearance of an
area of opacity, the white spot lesion.
 At
this earliest clinically visible stage,
the subsurface demineralization at the
microscopic level is well established.

The incipient lesion has been extensively
studied and is best described by
Silverstone.

Тhe observations of the incipient lesion
have been based on the use of a polarizing
microscope.

This microscope permits precise
measurements of the
amount of
space, called pore space,
which exists in normal enamel and
to a greater extent in enamel defects.

If demineralization progresses
more pore space occurs;

in contrast, during remineralization,
less pore space is
present.
Direct Connection of the Bacterial Biofilm to the
Body of the Lesion

Tooth enamel is composed of
interlocking structures called
enamel rods, which contain
billions of crystals.

The pores present between
the crystals and the rods
form a network of
channels that allow
diffusion of fluid, ions
and small molecules
The striae of Retzius extend this network
into deeper layers of the enamel.
This diffusion
network
allows:
The
channels
also allow
• remineralization of the
tooth throughout its life
• plaque acids to enter
the interior enamel,
causing
demineralization.
• the initial attack may
In
be on the ends of
demineralization
the enamel rods,
of the surface
• between the rods
enamel:
• or both.
Result from
this:
• widening of the areas
between adjacent rods
(inter-rod space)
When conditions
are optimum
ragged interface
between surface and
subsurface
can be
remineralized:
1. by the body
defenses, such
as calcium and
phosphate and
other ions from
the saliva,
2. through
preventive
strategies ,
such as fluoride
therapy
3. By reduction
of fermentable
carbohydrates
in the diet.
Reaching the enamel-dentin border,
whether any liquid causes
demineralization or remineralization
can move in 3 directions:
1-2. along the hypomineralized
EDJ in both direction – move
lateralli
3. into the dentinal tubules to the
pulp chamber
Diagram of a trichotomized
lesion (go in three directions )
attributable to diffusion of
acids:
-in both directions under the
enamel
- directly into the body of the
lesion in the dentin.
T, translucent zone;
B, body of the lesion;
R, reactionary dentin;
P, pulp.
(From Silverstone L. M., & Hicks, M. J.
(1985).
-
,
The
-
speed of progression of the caries
front depends on such factors as:
ion
concentration,
pH,
saliva flow
buffering actions
-all of them
continually
changing.
Any chemical changes in the plaque
can soon be reflected throughout
the enamel and dentin as part of the
incipient lesion.
The pores
allow
plaque
acids to be
directed
directly to
the
subsurface
region.
The initial acid attack
preferentially :
• dissolves the
magnesium and
carbonate ions,
followed by removal of:
• the less-soluble
calcium,
phosphate, and
other ions that are
part of the crystal.
 The
undermined surface zone
collapses.
 At
the same time, the more
soluble proteins are lost from
the subsurface matrix.
Cariogenic Bacteria

As a general rule, the cariogenic bacteria
metabolize sugars to produce the energy
required for their growth and reproduction.

The byproducts of this metabolism are acids,
which are released into the plaque fluid.

The damage caused by MS is mainly caused
by lactic acid, although other acids, such as
butyric and propionic, are present within the
plaque.
Measuring Plaque pH, the
Stephan Curve

There is a continuous pH change in
the plaque every time food is consumed.

There is an almost immediate drop in pH
when sugar or sugary snacks are eaten,
followed by a longer recovery period
than when other foods are eaten.

This drop-and-recovery curve has been termed
the Stephan curve;

Different individuals have different capabilities
to buffer acid production (see next fig.);

Studies have identified foods that are
accompanied by a drop the critical pH of 5.5 to
5.0,
such as dried fruits,
white bread, cereals,
starchy foods
Fig. Stephan curves. These curves show the typical plaque pH response
to an oral glucose rinse . An immediate fall in the pH is followed by a
gradual return to resting values after about 40 minutes.
The upper curve was obtained from milk and the lower one from an appledrink, showing a large difference in the acidogenicity of these two drinks.
The Relationship of Saturation to pH

The concentration of calcium and phosphate
ions in the plaque fluid bathing the tooth at
the plaque-tooth interface is extremely
important
because these are the same
elements that compose the
hydroxyapatite crystal found in the
enamel.
If the fluid adjacent to the tooth is
supersaturated with calcium and phosphate
ions at a given pH,
the enamel cannot undergo demineralization.
 The
saliva in contact with the teeth is
normally supersaturated with calcium and
phosphate, compared with the levels of these
minerals in enamel.
 The
bacterial plaque can concentrate
these ions to an even greater extent.
For instance, the number of calcium and
phosphate ions in plaque is 3 times
greater than the number in the saliva.
This increased concentration is of
practical importance because
calcium and phosphate levels tend
to be inversely related to the caries
score.
 As
the pH drops in an acid attack,
the level of supersaturation also
drops, and the risk of
demineralization increases.
There is no exact pH at which
demineralization begins, only a
general range of 5.5 to 5.0.
Demineralization is a function of both:
- a drop in pH ,
- the length of time that the enamel surface is
exposed to the acidic environment.
 Different plaques have:
- different initial pHs,
- different buffering potentials,
- different concentrations of calcium and
phosphate in different parts of the mouth.

A change in any of these variables
results in a different level of supersaturation in the
tooth environment.
Demineralization and
Remineralization Principles

Demineralization is caused by plaque acids,
which dissolve the tooth minerals making up
the basic calcium, phosphate, and hydroxyl
crystals of the enamel, dentin, and cementum.

Remineralization, requires the availability of
the same ions, preferably with fluoride as a
catalyst to reconstruct the missing or damaged
rods, a process that ten Cate called nonrestorative repair.
 The
crystals and fluoride
compound of most dental interest
in the demineralization and
remineralization process are:
hydroxyapatite (HAP),
- fluorhydroxyapatite (FHA),
- calcium fluoride (CaF2).
-
Enamel mineral
 The
mineral of enamel is a salt
formed from calcium phosphates.
 Basic
calcium phosphate in
enamel is hydroxyapatite.
Enamel mineral
 Apatite
- a mineral with chemical
formula
Са10(РО4)6 (F, OH)2


FHAFA
Ca10(PO4)6(F,OH)2
Ca10(PO4)6 F2
Enamel mineral
Other calcium phosphates:
СаНРО4.2Н 2О,
ß-tricalcium phosphate- Са 3(РО 4) 2
Brushite -
Octacalcium phosphate-
Са 8(РО 4) 4(НРО 4) 2.5Н 2О.
Dissociation equilibrium of hydroxyapatite
НА in liquid
medium
undergoes
electrolytic
dissociation
HA dissociates to :
10 calcium ions
6 trivalent phosphate ions
2 hydroxide ions
Са 10(РО 4) 6 (ОН)2 ←→ 10Са 2+ + 6РО43- +
2ОН -

Calcium and phosphate ions from the
enamel get into plaque :
- serve for buffering of the medium;

- if the environment is alkaline the iones can
reenter in enamel;
- part of the ions get into the saliva,
Processes of de-and remineralization of enamel in the oral environment
 Between
enamel and saliva is situated the
plaque biofilm
Ions entering the food diffuse plaque and
saturate it;
Within each eating into the plate enter acid,
and other acids are formed from microbial
metabolism.
Dissociation equilibrium of plaque acids

The acid is salt, and also in the liquid medium as well
as the crystal starts to dissociate.
hydrogen ions
+ acid anions
The active part of an acid is the hydrogen ion,
and its strength is dependent on the quantity
thereof.
The carious process is a
process of acid
demineralization
When in the solution around HA acid is
dissociate , begins the active effect of
hydrogen ions;
The hydrogen ions pass into the enamel
and move in competitive reaction with
calcium.
The hydrogen ions move into contact with the
hydroxyapatite and combined with the phosphate and
hydroxide ions of the crystal–
form a monohydrogen phosphate ion (НРО42+) and
(Н2О).
They quickly leave the crystal and move in solutionТе
Са 10(РО 4) 6(ОН) 2 ←→ Са 2+ + 6РО 43- + ОН ↓ Н+
НРО42+
Н20
↓ Н+
monohydrogen phosphate
Н2РО 4dihydrogen phosphate ion

Processes of de-and remineralization of enamel in
the oral environment
Enamel constantly washind from saliva.
The concentration of Ca2 + and PO4 ions in the
saliva varies - under normal conditions - 1,5 mmol /
l.
At neutral pH in the mouth the amount of Ca2 +
and PO4 ions is sufficient to saturate the medium.
These conditions provide balance in the process of
de-and remineralization and no significant ion
motion.
Processes of de-and remineralization of enamel in the oral environment
By acidification of the medium saturation with inherent
apatite ions decreased sharply
Starts quickly extracting of ions from enamel for her
saturation.
Critical pH = 5,5 - direction of movement of the ions only
in the direction from the enamel to the solution
performed only under demineralization
Performed only process of demineralization
By dissolving apatite:
over the enamel in the solution increases the concentration of Ca 2 +,
Mg2 + PO 43 -, HPO4 -, CO 32 - / HCO 3 - ions. + Ions from saliva
as a result of the action of saliva begins alkalization of the
medium
ions are directed to the enamel, enter it and precipitate to:
- dicalcium phosphate dihydrate (DCPD) or
oktakaltsiev phosphate (OCP)
in a favorable environment, they pass into the hydroxyapatite and,
in the presence of fluoride ions – to fluorhidroksiapatit
Thus is
realize the remineralization of tooth enamel
The long-term exposure of teeth to low
concentrations of fluoride (as found in
fluoridated water) results in the gradual
incorporation of fluoride into the existing
hydroxyapatite (HAP) crystals to form
fluorhydroxyapatite (FHA), which is more
resistant to acid damage.
Ендогенна Ф профилактика
 Conversely,
a higher concentration of
fluoride (as occurs with the use of topical
fluoride applications, fluoride dentifrices,
foams, and varnishes, etc.) results in the
formation of surface globules of CaF2
(as seen in electron microscope images).
 If
phosphates and proteins of the saliva
coat these globules, the globules become
more insoluble.
Локална Ф профилактика
When the fluoride is incorporated into
HAP to form FHA, it is said to be firmly
bound,
Fluoride in the form of CaF2, is loosely
bound and adsorbed onto the surface of
HAP and FHA crystals.
The Relationship between HAP, FHA,
and CaF2
After an attack by plaque acid(s),
- CaF2 dissolves first,
- followed in sequence by HAP,
- and finally, FHA (with its fluoride substitutions).


As the attack continues, the dissociated ions
increase the saturation level of the immediate
fluid , sufficiently to slow crystal dissolution and
eventually arrest further solution of the
crystals.
As the pH begins to return to normal, crystals
begin to re-form from the complex pool of
dissolved ions;
- some as HAP,
- some as FHA
(with many of the fluoride ions coming from the
previous CaF2).

 Any
deficiencies are
subsequently replaced, in time,
by calcium, phosphate, and
fluoride from sources such as the
saliva, water, and toothpastes.
system “breaks down”
(state of equilibrium -homeostasis)
when the attacks are too frequent
and too prolonged.
 The

end