口腔科学课件：1_2龋病.ppt

1.Definition Dental caries is caused by certain organism of the oral flora（菌丛）. It is an irreversible, slowly progressive decay of the hard tissues of individual teeth. the high incidence : 40-65% ↑ a multifactorial disease a chronic disease hard tissues of tooth: (enamel,cementum,dentin) an irreversible decay characterstic The carious process 2.Four Factors theory Four Factors Is Essential For The Initiation Of Dental Caries Namely: √ Cariogenic bacteria √ Food √ Host √ Time √ Cariogenic bacteria  ---Dental Plaque（牙菌斑） streptococcus mutans（变形链球菌） lactobacillus（乳酸杆菌） actinomyces（放线菌属） √ Food 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 consumption of the refined carbohydrate Tooth morphology bacterial plaque is an essential precursor of 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 buffering capacity has been lost, a low Ph environment is encouraged and persists longer Fluoride particular interest was the discovery of the association between fluoride concentration in water supplies and prevalence of dental caries in children √ Host √ Time Certain time is needed for the carious process Tetra-factor hypothesis microorganisms Host tooth substrate time caries The 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. Caries requires a susceptible host, a cariogenic oral