Microbiology of Dental Caries

1
Microbiology of Dental Caries
Shanghai Jiaotong University School of Medicine
Ninth Peoples Hospital Department of Oral
Medicine Z.TANG
2
Definition of dental caries
Caries is defined as localized destruction of the
tissue of the tooth by microbial action
3
Dental caries
Chronic endogenous infection
enamel
Oral flora
dentin
acids
pulp
cavity
demineralization
remineralization
balance
4
Aetiology
Plaque microorganisms
Host factors
Diet
Time
No microorganism no caries
5
Main microorganisms associated with caries
Lactobacillus
Oral Streptococci
??????
????
Actinomyces
Veillonella
????
????
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Oral Streptococci??????

mutans-group ??????
salivarious-group ??????
??????
anginosus-group ???????
mitis-group ?????
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Oral Streptococci
General characteristics
Ggram stainning positive
?????? Spherical or oval cocci in pairs and
chains Microaerophilic??? or facultative
anaerobic????
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mutans-group
S. mutans-group
mutans streptococci
S. mutans, ??(?)???serotypes c, e, f S.
sobrinus, ??(??)??? serotypes d, g S. cricetus,
serotype a S. rattus, serotype
b S. ferus serotype c S. macacae
serotype c S. downei, serotype h
8 serotypes a-h
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S. mutans
history
1924 Clark originaly isolated
1960s paid attention to it
S. mutans , its name derive from the fact that
cells can lose their coccal morphology and often
appear as short rods or as cocco-bacilli
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S. mutans c,e,f
Most common isolated species from dental plaque
Primary pathogen in enamel caries
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Antigen structure of mutans streptococcus
Lipoteichoic acid
Cell wall carbohydrate antigens
lipoproteins
Cell-wall
Cell wall-associated proteins
Antigen ?/?(antigen B or P1)
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Plaque formation
Extracellular polysaccharides ????
cariogenicity
Carbohydrate reserves
Intracellular polysacchrides ????
Converted to acid when dietary carbohydrates
unavailable
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Why was S. mutans considered as a putative
cariogenic bacterium?
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S. mutans pathogenic in caries
Importance in bacteria adhensive??
,co-aggregation ?? and colonization?? to tooth
surface
Ability to produce acid????Produce acid at an
extremely rate from pulses of fermentable
carbohydrate
Acid tolerance???Grow ,survive and produce acid
under low pH(4.55.0)
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S. mutans
Can adhesive to the tooth surface
Strong ability to produce acid
High acid tolerance
Play an important role in caries initiated
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salivarius-group
??????
S. salivarius S. vestibularis
?????
?????
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S. Salivarious ?????
colonizes mucosal surfaces, especially in the
tongue
produce an extracellular fructan
not considered as a significant opportunistic
pathogen
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anginosus-group
???????
S. constellatus S. intermedius S. anginosus
?????
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S. intermedius ?????
isolated mainly from liver and brain abscess
produce a protein toxin, termed intermedilysin
Not make extracellular polysaccharides from
sucrose.
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mitis-group
?????
S. sanguis S. gordonii S. parasanguis S.
oralis S. mitis S. crista
????
??(?)???
?????
?(??)???
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S. sanguis
produce extracellular soluble and insoluble
glucans from sucrose
????
produces a protease that can cleave sIgA
Initial adhensive in biofilm formation
Pioneer bacterium
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Lactobacillus
characteristics
????
G
Short rod or cocci rod
microaerophilic
Acidic pH(6.0)
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Lactobacillus
pathogenicity
Frequently isolated from deep carious lesions
High acid tolerance
Strong ability to produce acid
Play an important role in caries progress
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As the isolation of lactobacilli in large numbers
from saliva points to the presence of carious
activity,
they may be used as caries marker organisms,
????especially in epidemiological studies
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Actimyces
????
approximal sites and the gingival crevice.
associated with root surface caries increase
in numbers during gingivitis.
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General characteristics
G
ferment glucose metabolic end products
aerobic,facultative anaerobe or anaerobe

• pleomorphic in shape
• Short rods
• a true branching ,T,V,Y
• israelii filamentous.
• Some species (particularly A. naeslundii) are
  heavily fimbriated,

succinic, acetic and lactic acids
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Actimyces
A. naeslundii
A. israelii
?????
?(?)????
A. odontolyticus
A. viscosus
??(??)???
?????
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A. naeslundii
?????
produce an extracellular slime
a fructan from sucrose

produce a urease that may modulate pH in plaque
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A. naeslundii
?????
Two types of fimbriae can be found on the surface
of cells
cell-to-cell contact (co-aggregation)
cell-to-surface interactions
gingivitis
Root surface caries
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A. israelii
?(?)????
Cervicofacial region
Deep seated infections abdomen
actinomycosis
????
Uterine in woman
Sulfur granules
????
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A. odontolyticus
50 of strains form colonies with a
characteristic red-brown pigment
??(??)???
correlated with the very earliest stages of
enamel demineralization,
with the progression of small caries lesions
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Veillonella
characteristic
????
G-
Diplococci and in short chain
anaerobic
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Veillonella
Require lactate for growth
Unable to metabolize normal dietary carbohydrates
Used lactate produced by other microorganisms
Convert lactate into weaker acids(propionic acid)
A beneficial effect on dental caries
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Immunology of dental caries
bacteria
antigen
stimulate
B cell
Immune cells
sIgA
antibody
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Immunology of dental caries
Humoral immune
Cell immune
(predominant)
sIgA in saliva
IgG IgM in serum
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Immunization against dental caries
Artificial antigen
antigen
bacteria
B cell
Immune cell
Immune cells
sIgA
antibody
antibody
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Artificial active immunization
Artificial passive immunization
??????
??????
Artificial antigen
vaccine
Artificial antibody
??
Immune cells
antibody
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Artificial active immunization
Anti-caries vaccines
S. Mutans whole cell
Whole cell vaccines
GTFs , PAc, et al
Sub-unit vaccines
Nucleic acid vaccines
gtfB, pac
(Gene vaccines)
(DNA vaccines)
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Vaccine may produce its protective effect by
Inhibition of the microbial colonization of
enamel by sIgA
Interference with bacterial metabolism
Enhancement of phagocytic activity in the
gingival crevice area due to the opsonization??
of S. mutans with IgA or IgG antibodies
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Vaccines disadvantages
safety
The antibodies which develop after immunization
with most Strep. Mutans antigens tend to
cross-react with heart tissue, and the
possibility that heart damage could result has
made human vaccine trials very difficult
Weak immunogen
Only tested in animal experiments
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vaccines
Application future
unacceptible
acceptible
There are fears of possible side-effects which
would be unacceptible as caries is not a life
threstening disease(coss-react with heart tissue)
Developing countries with little or no organized
dental services and increasing prevalence of
caries
Prevention of disease in special high-risk
groups,e.g. mentally or physically handicapped
child
The incidence of dental caries is falling in the
West and the disease can be adequately controlled
using other techniques(Fluoridation)
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Artificial passive immunization
Heteroimmunization
cow
milk
IgG
????
Monoclonal antibodies against Pac, GTF
?????
Egg yolk antibody IgY
?????
Transgenic plants antibody tobacco
???????
Local used in oral cavity
toothpaste
mouth wash
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Artificial passive immunization
disadvantages
advantages
Persist time short
safety
convenience
Acceptable
May be an alternative caries-preventive strategy
for the future
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Microorganisms associated with root canal
infections
Way of root canal infection
Salivary contamination
Caries lesion
Gingival pocket
blood
45
Predominant microorganisms of root canal
infection
Gram-negative obligate anaerobic bacilli
Predominant
???????????
lesser
Facultative anaerobes
Aerobic bacteria
A little
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Bacteria associated with different types of root
canal infection
Porphyromonas endodontalis
Apical purulent inflammation
???????
P. gingivalis
Prevotella. intermedia
???????
?????
Apical portion of root canals with necrotic pulp
and periapical lesions
????,????
Actinomyces,Lactobacillus, Porphyromonas,
Prevotella, Peptostreptococcus, Veillonella
parvula, Enterococcus faecalis, Fusobacterium
nucleatum, and S. mutans
??????
????
??????,?????
????,?????,?????
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Porphyromonas endodontalis
???????
Black pigment
liposaccharides
Bacteria capsule
Virulence factors
antigens
Enzymes collagenase,hyaluronidase, fibrinolysin
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Microorganisms associated with clinical symptoms
of root canal infection
Pain, swelling, open sinus tract, tenderness to
percussion
Acute endodontic lesions
Actinomyces, Porphyromonas, Prevotella,
Peptostreptococcus, Veillonella parvula,
Porphyromonas endodontalis, and P. gingivalis
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Asymptomatic infections
P. denticola
?????
Acute periapical abscesses in children
P. melaninogenicus, P. oralis
???????
?????
Refractory periapical periodontitis
Actinomyces isrealii
?????
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Periapical infections
Streptococcus milleri, Peptostreptococcus
species, Peptococcus species
Alveolar bone
Soft tissue
Most commonly isolated
Orofacial infection
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Severe orofacial infections
Anaerobic gram-negative rods
Prevotella, Porphyromonas, and fusobacteria
Mild orafacial infections
gram-positive cocci and rods
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Immunopathology of pulpal disease
Pulpal and periapical tissue
Bacterial antigens
Cellular response
Humoral response
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Immune cells participate in pulpal disease
Neutrophils, plasma cells, T-helper lymphocytes,
T-suppressor lymphocytes, B-lymphocytes,
macrophages and mast cells
T cells more numerous than the B cells
T-helper and T-suppressor cells are approximately
equal numbers in chronic lesions
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neutrophils
??????
Provide one of the first lines of defensing
against the bacteria by phagocytosing whole cell
and their antigens
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Sensitized T lymphocytes
Respond to the bacterial antigens by releasing
soluble mediators or cytokines which can not only
potentiate the protective host response, but can
also cause tissue destruction
Sensitized B lymphocytes
Also produce some cytokines on exposure to the
sensitizing antigen and evolve into plasma cells
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Mast cells
Contribute to hypersensitivity reactions by
release of histamines and other active substances
upon reaction of antigens with mast cell IgE
Macrophages
play a role in processing of antigens for the
lymphocytes and in phagocytosis
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The elements necessary for immunopathology
present in different type infection
Inflamed dental pulp
Plasma cells containing IgG, IgA, IgM,and IgE
commonly occur,with 60 of the cells containing
IgG
The concentrations of IgG and IgA are elevated in
inflamed pulps compared normal pulps
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Periapical granulomas
Lymphocytes, plasma cells, polymorphonuclear
leukocytes, mast cells and macrophages
Acute apical abscesses
Elevated serum IgE levels
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Evaluation the contribution of immunity to the
pathogenesis of periapical infection
Immune response
Potentiate protective host response
Cause tissue destruction
60
May be postulated to play more of a destructive
than a protective role in most cases
Clinical significant
Clean antigen is very important in endodontics
Include not only bacteria and their products but
also denatured host tissues