Etiology of dental caries

Etiology of Dental Caries

上海交通大学医学院附属第九人民医院牙体牙髓病科

黄正蔚

九院牙体牙髓病科黄正蔚

Etiology is the study of causation. Derived from the Greek αἰτιολογία "giving a reason for"


What is this disease?

Color form Texture


To find the causes …


Cause of dental caries?


龋＝齿＋禹 ( 虫 )

虫

齿


Where are those worms

?


Other explanations ?

Might erosion be one cause?


Where is the acid ?


Anton van Leeuwenhook

17th Century


Louis Pasteur


chemico-parasitic hypothesis

—— WD. Miller(1890)

化学细菌学说


dietary carbohydrates

acid production

calcium phosphate

caries

oral bacteria

solubilize


SugarBacteria

from plaque Acid

Acid Healthy Tooth Decay


teeth + bread/carbohydrates + saliva demineralization

Miller’s experiments ：

teeth + meat/lipids + saliva non-demineralization

teeth + bread + boiled saliva non-demineralization

脱矿不脱矿


1. No bacteria no caries

germfree rats Sound teeth

Evidences for caries as an infectious disease

Bacteria seperated from caries inoculated ?


Streptococci seperated from caries lesion

inoculated

caries

2. Caries developed with bacteria inoculated



3. Antibiotics inhibited caries

Penicillin

caries


McClure & Hewitt 1946



4. Bacteria found in all caries specimens

Caries = lesion infected with bacteria microscopically


Dentinal tubules

Liquefaction focus

九院牙体牙髓病科黄正蔚infected affected

Carious human molar


Conclusion

dental caries may be caused by members of the commensal oral microflora


But …

Koch’s principles郭霍原则

For any microbe to be considered responsible for a given condition


Koch’s postulates

The microbe should be found in all cases


Koch’s postulates

The microbe should be grown on artificial media


Koch’s postulates

A pure subculture should produce the disease


And…

A high antibody titre to the microbe should be detected


What’s then?

No single microbe has been found which completely satisfies

Koch’s postulates for caries


Hypothesis on caries

ecological plaque hypothesis

Caries is a result of a shift in the balance of the resident microflora

生态菌斑学说


Reevaluation of the microbial aetiology of dental caries

Fermentable sugar

AcidDe-

mineralizationLow pH

S. oralisS. sanguis

Neutral pH

S. mutansLactobacilli

Re-mineralization

Enviromental Change

Ecological Change


Stephan curve


dental caries multifactorial disease


Introduction

“Plaque-Host-Substrate” theory

Host


Factor 1 Microbiota not only Bacteria


Definitions

Dental plaque (菌斑 ) Materia alba (软垢 ) Pellicle (获得性膜

) Calculus (牙结石

)


Dental plaque

Dental plaque is the soft, nonmineralized bacterial deposit which forms on teeth and dental protheses that are not adequately cleaned.

------ LÖe 1965


Dental plaque

Microscopically, plaque is simply confluent colonies of microorganisms connected by a matrix consisting predominantly of bacterial and salivary polymers.


What is dental plaque…

Bacteria deposit On hard surfaces Bacteria + matrix


erythrosin stained


Materia alba

bacterial aggregations, leucocytes and desquamated oral epithelial cells accumulating at the surface of plaque and teeth, but lacking the regular internal structure observed in dental plaque.


Differences betweenmateria alba and plaque

Bacteria composition Internal structure Adherence strength


Pellicle

an organic film derived mainly from the saliva and deposited on the tooth surface.


Calculus

calcified dental plaque, it is always covered with a superficial layer of noncalcified plaque.


Chemical composition of dental plaque (biofilm)

Dental plaque

(biofilm)

microorganisms

extracellular matrix

> 2X10 per gram per wet weight11


Function of extracellular matrix

carbohydrate reserve framework of the biofilm inflammation-inducing, toxic substances


Chemical composition of dental plaque (biofilm)

Dental plaque

(biofilm)

microorganisms

extracellular matrix

Inorganic content

Organic content

Protein 45%

Carbohydrate 15%

Lipid 12%

(Ca, P)


Formation of dental plaque


Formation of dental plaque

1 hr 30 d


Influence factors

Diet Age Salivary factors Oral hygiene Tooth alignment Systemic disease Host factors


Acquired enamel pellicle

Initial colonization


Micro-colonies


Microcolonies coalescing


Filamentousbacteria


“corn-cob” associations


Plaque formation

Acquired enamel pellicle formation Initial adherence and subcequent

proliferation Further aggregation


Formation Mechanisms

E N A M E L

Irreversible adhesion

Co-aggregation

Reversible adhesion


Formation Mechanisms

E N A M E L

Plaque formation Detachment


Remember…

Attachment, growth, removal and reattachment of bacteria is a continuous and dynamic process

Dental plaque will undergo continuous reorganization


Biofilm (生物膜 )


Bacteria living in planktonic (free swimming)

or in biofilm (dental plaque)?


Batch culture Biofilm


definition

Surface-associated bacterial community-forming microcolonies surrounded by a matrix of exopolymers


Dental plaque Biofilm ?


Biofilm communities

Sum of constitutive populations

Biofilm cellsAttached planktonic (liquid phase) cells

Why study biofilm?

1 + 1 2


Researches revealed …

cells growing as biofilm have unique properties, some of which have great clinical significance

General propertiesProtection from host defense and predatorsProtection from desiccation Protection from antimicrobial agents Surface-associated phenotype Slow growth rate Poor penetration Inactivation/neutralizationNovel gene expression and phenotypePersistence in flowing systemsSpatial and environmental heterogeneitySpatial organization facilitating metabolic interactionsElevated concentration of nutrients


Factor 2 Host


Tooth morphology

6

6

caries susceptibility


Tooth morphology

Pits & fissures Irregularities in arch form crowding overlapping


Tooth composition

Mineralization Trace elements fluoride


Enamel surface is more caries-resistant than the subsurface


Host factor : Saliva


Effect of desalivation on incidence and extent of caries in animals

caries


Decreased salivary flow and caries in humans

Xerostomia


Salivary flow rate Salivary composition and caries Salivary buffers Antibacterial factors of Glandular origin


Factor 3 Substrate: diet and caries


Epidemiological observations


Experimental caries of animals Caries

susceptibility


Controlled human studies: Vipeholm

Mental institution


Toffee Chocolate Caramel


Factor 4 Time


Thanks!

Etiology of dental caries

Health & Medicine

Transcript of Etiology of dental caries