Download Dental plaque

The History of caries
Over the years tooth decay has been
attributed to many factors.
The Syrians believed it was caused by
„tooth worms”; in the 18th and 19th
century it was thought to grow from
within the tooth.
DEFINITION
Dental caries is an infectious microbiologic
disease of teeth that results in localized
dissolution and destruction of the calcified
tissues..
tissues
Dental caries is a chronic, infectiou
infectiouss disease
initiated through a series of complex chemical
and microbial reactions associated with the
dental biofilm that results in the destruction
(decalcification, proteolysis) of the tooth
tissue..
tissue
CARIES
It develops often insidiously over a long period of time
progressing from the surface of the tooth to the interior.
Dental Plaque
A tenacious structure formed on tooth surfaces
which contain large numbers of closely packed
microorganisms surrounded by salivary
components and extracellular material of
bacterial origin
Cannot be removed by a stream of water or
Cannot
rinsing
Dental Plaque
Dental plaque – part of the defence
system of the host – protects enamel
from the colonization by exogenous
bacteria (pathogenic)
Properties of the bacteria associated
with the biofilm can differ from
planctonic cells
Dental Plaque
Plaque is not homogenous
Consists of:
- pellicle
- bacteria
- bacterial products
- salivary constituents
Composition:
one third = bacteria
two thirds = extracellular matrix
(secreted by bacterial cells; holds
microcolony together):
inorganic: calcium, phosphorus,
fluoride
organic:
bacterial byby-products: acids, enzymes,
toxins
saliva: proteins, sugars,
sugars, lipids
dietary carbohydrates
carbohydrates
leukocytes
epithelial cells
extracellular polysaccharides: dextran
Dental Plaque (SEM)
This scanning electron micrograph of caries-producing plaque illustrates the coccal
microorganisms usually found there. [Courtesy of Drs. Krutchkoff and Wei]
Appearance::
Appearance
fresh plaque:
transparent
stains pink
mature plaque:
heavier;fur
heavier;fur--like
Gray
Gray,, white,
white, yellow
stains red; clings to instrument
Location::
Location
common areas of mouth
individual teeth:
heaviest - cervical third
lightest - incisal third
supragingival vs. subgingival
can cover whole tooth (neglect)
forms on restorations, appliances
Wherever there is
plaque on the teeth
there is potential
caries formation, as
well as the
formation of
periodontal disease.
Here we see that
plaque unstained
can cover the tooth
completely.
If we use a disclosing
solution, which is usually a
food coloring agent and
have the individual rinse,
we notice that the amount
of plaque covering the
tooth is quite extensive.
Wherever there is mature
plaque, it will absorb the
disclosing solution.
Plaque
Examination of the
individual's mouth showed
that he had a relatively
clean mouth. There was
some gingival
inflammation, but nothing
too extreme just early
signs of gingivitis. The
important issue here is
that the teeth were well
aligned, appeared to be
quite clean and there
were no apparent caries.
Plaque
Before the individual began
participation in the project, a
thorough prophylaxis removed all the
areas of plaque formation, and
flossing intraproximally removed any
residual plaque formation.
Plaque
When the individual returned the
following day after 24 hours the
teeth were once again disclosed.
disclosed. The
appearance now demonstrated an
increased plaque formation on the
teeth..
teeth
Plaque
This appearance of plaque formation presented
48 hours after nonnon-brushing or mechanical
removal of the plaque. Notice how the teeth are
almost completely covered with plaque. The
reason that the incisor edges of the maxillary
incisor teeth appear to be plaque free was
because the individual rubbed his teeth with a
towel, as he expressed the teeth felt furry and he
was too uncomfortable.
Plaque
Notice the posterior teeth are almost
completely covered. So, the lesson to be
learned here is that the mechanical removal
of plaque is essential to maintain a sound
oral health. And remember that wherever
plaque formation occurs dental caries also
might occur.
Stages of formation:
1.
acquired pellicle forms
2.
colonization:
initial colonization (adherence) of bacteria
to pellicle
multiplication
3.
development of extracellular matrix
(slime layer)
secreted by bacteria
anchors bacteria to tooth
provides protection from host response
4.
growth and maturation
plaque ages; new colonizers adhere to
previously attached cells; bacteria cluster
together
colony blooms into mushroom shape
channels exist that allow fluid movement
Plaque Bacteria
days 11-2:
Streptococci
some rods
days 22-4:
rod increase
fusiform bacilli and filamentous
m/o appear
days 44-7:
rods increase; filamentous increase
spirochetes and vibrios appear
plaque thickens
Plaque Bacteria
days 77-14:
spirochetes and vibrios increase
white blood cells increase
anaerobic conditions
signs of inflammation in gingiva
days 1414-21+:
older plaque
vibrios and spirochetes prevalent
Factors influencing plaque
formation:
types of bacteria
role of saliva
diet (although food not required)
presence of other deposits
oral hygiene habits
poor dentistry
malignment
Acquired Pellicle
An organic film on tooth enamel surfaces formed by
selective adsorption to apatitic surfaces of specific
glycoproteins of salivary origin.
Acellular, structureless
Comprised of:
- aminoacids
- carbohydrates
derived from saliva
Enamel Pellicle (EM)
Enamel pellicle (arrow) is the uniform thick
deposition of salivary protein between a
thin layer of immature bacterial plaques
and enamel. [Courtesy of Drs. Krutchkoff
and Wei]
Acquired Pellicle
Protective functions:
1) restrict diffusion of acids
2) antibacterial factorsfactors-sIgA,
Lysozyme, C3
3) helps to counteract acid pH
4) FF-, Ca, P bound in pellicle layer
5) may reduce bacterial attachment
Acquired Pellicle
Damaging functions:
1) initial step in dental plaque
formation
2) selective bacterial adhesion
3) can promote staining of dental
surfaces
Microbial aetiology of caries
Gnotobiotic animal studies showed that caries
could be induced by specific bacteria, especially
members of the mutans streptococcistreptococci-group
(eg. Streptococcus mutans and Strep.
sobrinus), when fed a cariogenic (high
sucrose) diet.
the potential for transmission from animal to
animal
protection could be achieved by antimicrobial
agents and vaccination and by passive
immunisation (when antibodies from another
source are applied to teeth).
Flora of the Mouth
Gram ((-)
-Prevotella melaninogenica
-Fusobacterium nucleatum
-Veillonella spp.
Gram (+)
-Lactobacillus
-Actinobacillus, Actinomyces
Others
Flora of the Mouth
Pioneer speciesspecies- Earliest colonizers
-S. salivarius
-S. mitis
-S. oralis
-S. sanguis
-S. mutans
Flora of the Carious Lesion
Smooth surface: S. mutansmutans-very significant
S. sanguis
Pits and fissures: -mutans Streptococci
Streptococci--very
significant
-S. salivarius
-Lactobacillus spp. very
significant
Flora of the root surface: Actinomyces spp.
Streptococcus spp
Pits and fissures are the most caries prone
Bacteria in Carious Lesions
(Summary)
mutans Streptococci can be isolated more often in
higher numbers from a range of carious lesions
advanced lesions generally yield a more diverse
microflora including acidogenic and proteolytic
species working together
mutans Streptococci are not always present
when there is caries
There is a role for other bacteria
Pathogenic Properties of Cariogenic
Bacteria
Produce Extracellular Polysaccharides (EPS) and
Intracellular Polysaccharides (IPS)
-EPS
EPS--glucans, fructans-fructans--contribute
contribute to plaque
matrix
-IPSIPS-glycogen like storage compounds, can be
used for energy production and converted to
acid when free sugars are not available
Ability to maintain sugar metabolism in a low pH
Pathogenicity of cariogenic bacteria
Rapid transport of dietary sugars: the
sugar phosphotransferase uptake
system is a high affinity process. Mutans
streptococci possess more than one sugar
transport system.
Rapid rates of glycolysis (acidogenicity):
can result in a terminal pH of below 4.5 in
only a few minutes.
Pathogenicity of cariogenic bacteria
Tolerance of, and growth at, low pH
(aciduricity): the growth of many of the
bacteria found on sound enamel (eg.
Strep. Sanguis)
Sanguis) is inhibited at pH <5.5,
whereas this is optimal for cariogenic
species.
— Intracellular polysaccharide
synthesis (IPS): can be used during
starvation conditions and catabolised to
acid when dietary sugars are not available
Pathogenicity of cariogenic bacteria
A striking feature of the main
cariogenic bacteria (mutans
streptococci and lactobacilli) is their
combined acidogenicity and
aciduricity; mutans streptococci but
not lactobacilli produce EPS.
Pathogenicity of cariogenic bacteria
• — Extracellular polysaccharide synthesis
(EPS): these polymers help make up the plaque
matrix.
• Glucosyltransferases (GTF's) convert sucrose
to soluble and insoluble glucans, that help
consolidate bacterial attachment; Strep. mutans
also produces a specific highly insoluble polymer
(mutan).
•
Fructosyltransferases (FTF's) convert sucrose
to fructans; these polymers are labile and can
be used by plaque bacteria as an energy source.
Substrate
Contributions of Diet
-Sugar
-Simple sugars diffuse acid into plaque
-Bacteria produce acid from sugar
-Brief sugar exposure leads to rapid decrease in
plaque pH
-Repeated sugar consumption leads to demineralization
of tooth
Plaque control:
control:
professionally
patient’s role
the longer plaque biofilm remains undisturbed, the
greater the pathologic potential
research
significance to disease (caries; periodontal)
biofilm structure protects bacteria, making removal
difficult
physical removal of plaque biofilm is necessary, and
most effective for controlling disease