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 )

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

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

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

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

Caries En Esmalte. Caries Dental.

Dental Caries

Dental Caries, dental

Guia Caries Dental

Biofilme PC II mod - Portal FOP-Unicamp · Interação entre diferentes microorganismos no biofilme NIKIFORUK, G. Understanding dental caries – etiology and mechanisms . 1985.

CARIES DENTAL