EtiologyofDentalCaries

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,Etiology is the study of causation. Derived from the Greek giving a reason for,What is this disease?,Color,Form,Texture,To find the causes ,Cause of dental caries?,龋, 齿 禹(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,Sugar,Bacteria from plaque,Acid,Acid,Healthy Tooth,Decay,Millers experiments：,脱矿,不脱矿,1. No bacteria no caries,germfree rats,Sound teeth,Evidences for caries as an infectious disease,?,Streptococci seperated from caries lesion,caries,2. Caries developed with bacteria inoculated,Evidences for caries as an infectious disease,3. Antibiotics inhibited caries,Penicillin,caries,Evidences for caries as an infectious disease,McClure & Hewitt 1946,Evidences for caries as an infectious disease,4. Bacteria found in all caries specimens,Caries = lesion infected with bacteria microscopically,infected,affected,Carious human molar,Conclusion,dental caries may be caused by members of the commensal oral microflora,But ,Kochs principles郭霍原则,For any microbe to be considered responsible for a given condition,Kochs postulates,The microbe should be found in all cases,Kochs postulates,The microbe should be grown on artificial media,Kochs postulates,A pure subculture should produce the disease,And,A high antibody titre to the microbe should be detected,Whats then?,No single microbe has been found which completely satisfies Kochs 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,Acid,De-mineralization,Low 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. - Le 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 depositOn hard surfacesBacteria + 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 structureAdherence 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),Function of extracellular matrix,carbohydrate reserve framework of the biofilminflammation-inducing, toxic substances,Chemical composition of dental plaque (biofilm),Dental plaque(biofilm),(Ca, P),Formation of dental plaque,Formation of dental plaque,1 hr,30 d,Influence factors,DietAgeSalivary factorsOral hygieneTooth alignmentSystemic diseaseHost factors,Acquired enamel pellicle,Initial colonization,Micro-colonies,Microcolonies coalescing,Filamentousbacteria,“corn-cob” associations,Plaque formation,Acquired enamel pellicle formationInitial adherence and subcequent proliferationFurther aggregation,Formation Mechanisms,E N A M E L,Irreversible adhesion,Co-aggregation,Reversible adhesion,Formation Mechanisms,Plaque formation,Detachment,Remember,Attachment, growth, removal and reattachment of bacteria is a continuous and dynamic processDental 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,?,Why study biofilm?,Researches revealed ,cells growing as biofilm have unique properties, some of which have great clinical significance,Factor 2 Host,Tooth morphology,Tooth morphology,Pits & fissuresIrregularities in arch formcrowdingoverlapping,Tooth composition,MineralizationTrace elementsFluoride,Enamel surface is more caries-resistant than the subsurface,Host factor : Saliva,Effect of desalivation on incidence and extent of caries in animals,Decreased salivary flow and caries in humansXerostomia,Salivary flow rateSalivary composition and carie