Microbiology of Dental Caries

Shanghai Jiaotong University School of Medicine Ninth People’s Hospital Department of Oral Medicine Z.TANG

Definition of dental caries

Caries is defined as localized destruction of the tissue of the tooth by microbial action

Oral flora

acids

demineralization remineralizationcavity

Chronic endogenous infection

balance

enamel

dentin

pulp

Dental caries

Aetiology

Host factors

Plaque microorganisms

Diet

Time

No microorganism no caries

Main microorganisms associated with caries

Oral Streptococci Lactobacillus

Actinomyces Veillonella

口腔链球菌属 乳杆菌属

放线菌属 韦荣菌属

Oral Streptococci 口腔链球菌属mutans-group变形链球菌群 salivarious-group唾液链球菌群

anginosus-group 咽峡炎链球菌群 mitis-group 轻链球菌群

变异链球菌群

Oral Streptococci General characteristics

G ＋ gram stainning positive 革兰染色阳性Spherical or oval cocci in pairs and chains

Microaerophilic 微需氧 or facultative anaerobic 兼性厌氧

S. mutans, 变形（异）链球菌 serotypes c, e, fS. sobrinus, 远缘 ( 表兄）链球菌 serotypes d, gS. cricetus, serotype aS. rattus, serotype bS. ferus serotype cS. macacae serotype c S. downei, serotype h 8 serotypes a-h

mutans-group S. mutans-group mutans streptococci

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

S. mutans c,e,f

Most common isolated species from dental plaque

Primary pathogen in enamel caries

Antigen structure of mutans streptococcus

Cell wall carbohydrate antigens Lipoteichoic acid

lipoproteins Cell-wall

Cell wall-associated proteins Antigen /Ⅰ Ⅱ（ antigen B or P1)

Extracellular polysaccharides胞外多糖Plaque formation

cariogenicity

Intracellular polysacchrides胞内多糖Carbohydrate reserves

Converted to acid when dietary carbohydrates unavailable

Why was S. mutans considered as a putative cariogenic bacterium?

S. mutans pathogenic in caries

Ability to produce acid 产酸能力 :Produce acid at an extremely rate from pulses of fermentable carbohydrate

Acid tolerance 耐酸性 :Grow ,survive and produce acid under low pH(4.5~5.0)

Importance in bacteria adhensive 黏附 ,co-aggregation共聚 and colonization 定植 to tooth surface

S. mutans

Can adhesive to the tooth surface

Strong ability to produce acid

High acid tolerance

Play an important role in caries initiated

S. salivariusS. vestibularis

salivarius-group唾液链球菌群 唾液链球菌前庭链球菌

S. Salivarious 唾液链球菌colonizes mucosal surfaces, especially in the tongue

produce an extracellular fructan

not considered as a significant opportunistic pathogen

S. constellatusS. intermediusS. anginosus

anginosus-group咽峡炎链球菌群

中间链球菌

S. intermedius 中间链球菌isolated mainly from liver and brain abscess

produce a protein toxin, termed intermedilysin

Not make extracellular polysaccharides from sucrose.

S. sanguisS. gordoniiS. parasanguisS. oralisS. mitisS. crista

mitis-group

血链球菌格登（氏）链球菌口腔链球菌轻（缓症）链球菌

轻链球菌群

S. sanguis produce extracellular soluble and insoluble glucans from sucrose

produces a protease that can cleave sIgA

Initial adhensive in biofilm formation“Pioneer bacterium”

血链球菌

Lactobacillus characteristics

G ＋

Short rod or cocci rod

microaerophilic

Acidic pH(6.0)

乳杆菌属

Lactobacillus pathogenicity

High acid tolerance

Strong ability to produce acid

Frequently isolated from deep carious lesions

Play an important role in caries progress

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”, 龋标志菌 especially in epidemiological studies

Actimyces

approximal sites and the gingival crevice.

associated with root surface caries

increase in numbers during gingivitis.

放线菌属

succinic, acetic and lactic acids

General characteristics

pleomorphic in shape

Short rodsa true branching ,T,V,Y A. israelii filamentous. Some species (particularly A.

naeslundii) are heavily fimbriated,

G ＋

aerobic,facultative anaerobe or anaerobe ferment glucose metabolic end products

Actimyces

A. naeslundii

内氏放线菌A. israelii

依（衣）氏放线菌A. odontolyticus

溶牙（龋齿）放线菌A. viscosus

黏性放线菌

A. naeslundii

produce an extracellular slime a fructan from sucrose

produce a urease that may modulate pH in plaque

内氏放线菌

Two types of fimbriae can be found on the surface of cells

cell-to-cell contact (co-aggregation) cell-to-surface interactions

A. naeslundii

Root surface caries gingivitis

内氏放线菌

A. israelii

actinomycosis

Sulfur granules

Cervicofacial region

Deep seated infections abdomen

Uterine in woman

依（衣）氏放线菌

放线菌病

硫磺颗粒

A. odontolyticus50% 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

溶牙（龋齿）放线菌

Veillonella韦荣菌属

G －

Diplococci and in short chain

anaerobic

characteristic

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

Veillonella

Immunology of dental caries

antigen bacteria

Immune cells

antibody

B cell

sIgA

stimulate

Immunology of dental caries

Humoral immune Cell immune

sIgA in saliva

IgG IgM in serum

(predominant)

Immunization against dental caries

antigen

Immune cells

antibody

bacteria

B cell

sIgA

Artificial antigen

Immune cell

antibody

Artificial active immunization Artificial passive immunization自动免疫接种 被动免疫接种

Artificial antigen vaccine

Immune cells

antibody

Artificial antibody疫苗

Artificial active immunization Anti-caries vaccines

S. Mutans whole cell Whole cell vaccines

GTFs , PAc, et al Sub-unit vaccines

Nucleic acid vaccines

(Gene vaccines)

(DNA vaccines)

gtfB, pac

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 调理 of S. mutans with IgA or IgG antibodies

Vaccines disadvantages

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

safety

vaccines

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)

The incidence of dental caries is falling in the West and the disease can be adequately controlled using other techniques(Fluoridation)

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

Application future

Artificial passive immunization

Heteroimmunization cow milk IgG异种免疫Monoclonal antibodies against Pac, GTF单克隆抗体Egg yolk antibody IgY 鸡卵黄抗体Transgenic plants antibody tobacco 转基因植物抗体Local used in oral cavity toothpaste mouth wash

Artificial passive immunization

advantages

safety

convenience

Acceptable

disadvantages

Persist time short

May be an alternative caries-preventive strategy for the future

Microorganisms associated with root canal infections

Way of root canal infection

Salivary contamination Caries lesion

Gingival pocket blood

Predominant microorganisms of root canal infection

Gram-negative obligate anaerobic bacilli

革兰阴性的专性厌氧杆菌Facultative anaerobes

Predominant

lesser

Aerobic bacteriaA little

Bacteria associated with different types of root canal infection

Apical purulent inflammationPorphyromonas endodontalis

P. gingivalis Prevotella. intermedia牙髓卟啉单胞菌

牙龈卟啉单胞菌 中间普氏菌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

放线菌属 , 乳杆菌属 卟啉单胞菌属 普氏菌属

消化链球菌属 , 极小韦荣菌粪肠球菌 , 聚核梭杆菌 , 变形链球菌

Porphyromonas endodontalis 牙髓卟啉单胞菌Black pigment

Virulence factors

liposaccharides

Bacteria capsule

Enzymes: collagenase,hyaluronidase, fibrinolysin

antigens

Microorganisms associated with clinical symptoms of root canal infection

Acute endodontic lesions Pain, swelling, open sinus tract, tenderness to percussion

Actinomyces, Porphyromonas, Prevotella, Peptostreptococcus, Veillonella parvula, Porphyromonas endodontalis, and P. gingivalis

Asymptomatic infections P. denticola

Acute periapical abscesses in children

P. melaninogenicus, P. oralis

齿垢普氏菌

产黑色素普氏菌 口腔普氏菌Refractory periapical periodontitis

Actinomyces isrealii 依氏放线菌

Periapical infections

Alveolar bone

Soft tissue

Orofacial infection

Streptococcus milleri,

Peptostreptococcus species,

Peptococcus species

Most commonly isolated

Severe orofacial infections

Prevotella, Porphyromonas, and fusobacteria

Anaerobic gram-negative rods

Mild orafacial infections

gram-positive cocci and rods

Immunopathology of pulpal disease

Pulpal and periapical tissue Bacterial antigens

Cellular response Humoral response

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

neutrophils

Provide one of the first lines of defensing against the bacteria by phagocytosing whole cell and their antigens

嗜中性粒细胞

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

Mast cells

Contribute to hypersensitivity reactions by release of histamines and other active substances upon reaction of antigens with mast cell IgE

play a role in processing of antigens for the lymphocytes and in phagocytosis

Macrophages

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

Periapical granulomas

Lymphocytes, plasma cells, polymorphonuclear leukocytes, mast cells and macrophages

Acute apical abscesses

Elevated serum IgE levels

Evaluation the contribution of immunity to the pathogenesis of periapical infection

Immune response

Potentiate protective host response Cause tissue destruction

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