学习龋病学需要了解的人

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1、Dental CariesOuyang Yong Associate professorDepartment of Endodontics and Operative DentistrySun Yat-sen University岳松龄岳松龄王满恩王满恩史俊南史俊南刘正刘正樊明文樊明文李玉晶李玉晶王嘉德王嘉德周学东周学东高学军高学军凌均棨凌均棨刘天佳刘天佳学习龋病学需要了解的人学习龋病学需要了解的人史俊南刘正樊明文李玉晶周学东凌均棨吴补领高学军Photos of dental cariesPhotos of dental cariesPhotos of dental caries Caries

2、 is Latin for rot or rotten.Dental caries means rotten teeth.Caries is the noun which names the disease Carious is the adjective,not a caries,a carious area or an area of caries.Dental caries can be defined asChronic progressive deconstructive disease of hard dental tissues Bacterial infected diseas

3、es caused by specific bacteriaa reversible multifactorial process of tooth demineralization and remineralization.Dental caries Dental caries,a bacterial infection,may be define as a posteruptive pathological process of external origin,involving the softening of the hard dental tissue and proceeding

4、to cavity formation.This is distinct from the dissolution of the hard dental tissues of an unerupted tooth which is not dental caries but tooth resorption.The carious process a pathological process of localized destruction of calcified tooth tissues by acids produced by organisms.Etiologically carie

5、s is considered a multi-factorial disease,which involves interplay between the host(saliva and teeth)micro organisms (streptococcus mutans),and the substrate(dietary carbohydrate sucrose),with the production of Lactic acid.Dental plaque(Bio-film)serves as the medium for caries development.Basic path

6、ological changes demineralization of inorganic tissues of tooth Disintegration of the organic tissues of tooth involves enamel,dentin,cementum Epidemiology of dental caries流行病学流行病学Prevalence rate（患病率）（患病率）：is the proportion of a population affected by a disease of a condition at one point time.Incid

7、ence（发病率）：（发病率）：is a mesurement of the rate at which a disease progresses the increase or decrease in the number of new cases occurring in a population within the same time periodMeasuring caries activityDMF indexD the mean number of decayed teeth with untreated carious lesionsM the mean number of t

8、eeth which have been extracted and are therefore missingF the mean number of filled teethDMF(T)to denote decayed,missing,and filled teethDMF(S)to denote decayed,missing,and filled surfaces in permanent teethdmf(t)dmf(s)similar indices for the primary dentitionFrequency distribution of dental caries

9、according to various tooth location permanent dentition Deciduous dentitiondistribution of dental caries according to tooth surface Occlusal interproximal buccalCaries is world wide in its distribution 1.The prevalence of dental caries increases with the development of economy 2.High DMF before 1970

10、 in the industrialized country To decrease after 1970 in the industrialized country3.More prevalence in industrialized than in the third word country4.Caries experience tends to increase in the developing country and decline in many western countries.5.Caries experience is higher in urban than in ru

11、ral communities in developing countries.Prevalence of dental caries(1995)，special for 12-18Y age groupsis increased significantly （20-40%）In recent 10 years,prevalence of dental caries in primary dentition is increased significantly than the permanent Why has caries prevalence decreased in modern po

12、pulation?The is possibly attributable to 1.The fluoridation of drinking water,use of fluoride toothpastes and improved oral health 2.A changing pattern of sugar consumption3.A decrease in virulence(毒力)of the organsims Aetiology of dental caries龋病的病因学龋病的病因学原发性釉护膜原发性釉护膜(primary enamel cuticle)残余釉上皮残余釉

13、上皮（reduced enamel epithelium)获得性膜获得性膜（acquired pellicle）食物碎片食物碎片（food debris,material alba）牙菌斑（牙菌斑（dental plaque）牙结石（牙结石（calculus,tartar）The organic deposits on the enamel surface four factors is essential for the initiation of dental caries,namely:1.Micro-organism mutans streptococci Lactobacilli A

14、ctinomyces2.Substrate Refined carbohydrates(精制碳水化合物)such as sucrose蔗糖 provide a suitable substrate on which the cariogenic micro-organisms act to produce the acids that lead to dissolution of the hard dental tissues Caries experience is influenced by the quantity,quality and especially frequency of

15、consumption of the refined carbohydrate 3.Susceptible teeth易感牙The ingestion of fluorides during tooth mineralization leads to the formation of fluor-apatite in enamel.Its presence in enamel makes the tooth less susceptible to dental caries because it is less soluble in acid than the hydroxyapatite(羟

16、磷灰石)which is normally present in the hard dental tissues4.Time All the factors should be present for sufficiently long time for the caries process to be initiated.Definition:Dental plaque（牙菌斑）（牙菌斑）Classification of Dental plaquesupragingival plaque -dental cariessubgingival plaque -periodontal disea

17、sesSTRUCTURE OF DENTAL PLAQUEPlaque on smooth surface Plaque-dental surface Middle layer-condensed microbial layer body of plaque The surface layer of plaquePlaque in pit and fissureComposition of Dental plaquebacteria which form 50-70%of dental plaque a small number of epithelial cells Leukocytes M

18、acrophagesglycoproteins which,together with extracellular polysaccharides,form the plaque matrixmucopolysaccharides(粘多糖)such as glucans and fructans(右旋糖)Inorganic components calcium phosphorus fluorides.MECHANISMS OF PLAQUE FORMATIONThe attachment,growth,removal and reattachment of bacteria to the t

19、ooth surface is a continuous and dynamic process.Several distinct processes can be recognized lAbsorption of salivary proteins and glycoproteins,together with some bacterial molecules,to the tooth surface to form a conditioning film(the acquired pellicle).获得性膜的形成获得性膜的形成lnon-specific interaction of m

20、icrobial cell surfaces with the acquired pellicle via van der Walls attractive forces.Irreversible adhesion can occur if specific inter-molecular interactions take place between adhesions on the cell surface and receptors in the acquired pellicle.Secondary or late-colonizers attach to primary coloni

21、zers(coaggregation共集共集),also by specific inter-molecular interactions.FORMATION AND DEVELOPMENT OF DENTAL PLAQUE1.Formation of acquired pellicle and primary aggregation2.Bacteria growth and development3.The mature of dental plaqueDevelopment Pellicle formation Microorganisms do not attach thermselve

22、s directly to the mineralized tooth surface and the teeth are always covered by an a cellular proteinaceous film,the pellicleForms on the“naked”tooth surface within minutes to hours Salivary glycoproterns Carbohydrates Lipid a lesser extent components from the gingival crevicular fluid(龈沟龈沟液液)Major

23、constituents of Pellicle1.Because of its selective nature restrict transportation of irons in and out of the dental hard tissue.It may play an important modifying role in caries2.Provide further protection against demineralization of the enamel3.Modify the number of potential adsorption sites for di

24、fferent bacterial species4.As the substrate for the microorganisms Function of Pelliclemicrobial colonizationInitial microbial colonization streptococcus mutans(变形链球菌变形链球菌)accounting for 56%of the total initial microflora Actinomyces spp(放线菌放线菌)a minor proportion gram-negative bacteria(G-)Microbial

25、succession The initial establishment of a streptococcal flora appears to be a necessary antecedent for the subsequent proliferation of other organisms The most striking changed is shift from streptococcus-dominated plaque to plaque dominated by Actinomyces.MICROBIAL AETIOLOGY OF CARIES animal studie

26、s micro-organisms are involved in the aetiology of dental caries ncariogenic microorganisms Streptococcus mutanslactobacillus ActinomycesCariogenic properties(致龋菌的特性致龋菌的特性)1.they are able to produce acid rapidly from fermentable carbohydrates(acidogenic).2.They thrive under acid conditions(aciduric)

27、3.able to adhere to the tooth surface because of their ability to synthesize sticky extracelluar polysaccharides from dietary sugarsAdvanced lesions often have a high proportion of lactobacillidentinal lesions have a diverse micro flora with many Gram positive Gram negative bacteria.Root surface car

28、ies was originally associated with Actinomyces spp.but recent studies suggest a similar aetiology to enamel cariesRampant caries can occur in xerostomic patients and in infants fed with high levels of sugar in pacifiers(nursing bottle caries).The plaque contains high levels of mutans streptococci an

29、d lactobacilli.Micro-organism and cariesHypotheses and theory relating to Aetiology of dental caries1.Chemico-parasitic theory(化学细菌学说)This postulates that oral bacteria act on sugar to produce acid which demineralizes the inorganic component of enamel,resulting in the development of a carious lesion

30、.2.Proteolytic theory(蛋白溶解学说)It is thought that the organic component of enamel is first broken down by proteolytic enzymes,opening up path-ways for bacteria to attack the enamel by other processes such as by acid or by chelation.3.Chelation theory(螯合学说)This postulates that enamel is demineralized b

31、y chelating agents at neutral pH.Protein breakdown products as well as lactic acid are some chelating agents known to exist in nature.4.Auto-immunity theory In this theory,it is suggested that forbidden clones of lymphocytes attack target cells(odontoblasts)rendering the tooth vulnerable to caries a

32、ttack.5.Four foctors theoriesmicroorganismsHost&toothsubstratetimecariesThe four circle diagrammatically represent the parameters involved in the carious process.All four factors must be acting concurrently(overlapping of the circles)for caries to occur.The role of dietary carbohydrate Nutrition-sys

33、temic dietary effects Diet -local dietary effects Caries prevalence is low in populations adhering to a primitive way of living and a diet of local products with little sugar A drastic increase in caries is invariably seen when these population“improve”their standard of living and adopt a modern“civ

34、ilized”diet with high sugar content A strong correlation between caries development and sugar consumption epidemiological studiesSucrose(蔗糖蔗糖)-called the arch-criminal in dental caries Monosaccharides ,disaccharides and of the polysaccharide starch can be fermented to acid by the plaque bacteria Sor

35、bitol（山梨糖）（山梨糖）xylitol(木糖醇木糖醇)-sugar substitutes used in sugar-free chewing-gumsDietary habits and caries prevalenceHost&tooth(susceptible teeth)It was a clinical experience that not all individuals with poor oral hygiene and frequent sugar consumption develop caries In the laboratory,extracted teet

36、h exposed to the same acidic buffer challenge certainly do not develop artificatial caries-like lesions to the same degree within a short period of time Tooth morphology:susceptible sites Environment of the tooth:Saliva fluorideHost&toothTooth morphology bacterial plaque is an essential precursor of

37、 caries,sites on the tooth surface which favour palque retention and stagnation are particularly prone to decay Saliva under normal conditions,the tooth is continually bathed in saliva.It is capable of remineralizing the early carious lesion because it is supersaturated with Ca and P.when salivary b

38、uffering capacity has been lost,a low Ph environment is encouraged and persists longerFluoride particular interest was the discovery of the association between fluoride concentration in water supplies and prevalence of dental caries in children 1.It is evident that the mere existence of the three fa

39、ctors operating together does not result in instantaneous mineral loss 2.therefore a fourth circle is often added to stress the time dimension taken for dental caries to develop Time Other factorsAgeSexGeographyRaceEconomics statusNutritionHealth statusThank you for your attention!jhfdb986420-(&$#YW

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