【文章內容簡介】 A fourth factor time must be considered in any discussion of the etiology of caries. Diagrammatically,these factors can be portrayed as four overlapping circles. Micro anisms host amp。 tooth Sub strate The four circles diagrammatically represent the factors involved in the carious four factors must act concurrently (overlapping of the circles)for caries to occur time no caries no caries no caries no caries caries Caries requires a susceptible host, a cariogenic oral flora and a suitable substrate that must be present for a sufficient length of time Saliva the term saliva refers to the mixture of secretions in the oral carity ?Saliva is produced day and night and it is constantly swallowed ?Saliva is present as a proteinaceous film covering all surfaces of oral cavity This mixture consists of fluids derived from ? the major salivary glands ? minor glands of oral mucose ? traces from gingival exudate Effect of desalivation on incidence and extent caries in animals Effect of desalivation on caries in hamsters Gruop No. hamsters Avg. no. carious teeth Avg. caries score Intact Salivary glands 20 Desalivated* 10 *Parotid, submandibular, and sublingual glands. Decreased salivary flow and caries in humans ?Sarcoidosis ?Sjogren’s syndrome ?Tharapeutic radiation Hydrogen ion Buffering ability Calcium Inanic phosphate Fluoricle Inanic ponents Organic ponents mucins Glycoproteins Statherin and acidic prolinerich proteins amylase Antrmicrobial proteins Saliva and dental caries the quantity of saliva associated with caries experience Relationship between salivary characteristics and caries prevalence Property Relationship Property Relationship Flow rate 177。 pH Ca Buffer capacity + PO4 NH3 Amylase Viscosity Urea Salivary position and caries Antibacterial factors of glandular origin could protect oral mucosal and hard surfaces by helping to regulate the quantity and species distribution of oral microbes Oral Microanisms and dental plaque In contrast to mucosal surfaces, the surfaces of teeth are not constantly renewed by shedding of colonized epithelial cells. Surfaces of teeth Some special sites occlusal fissues Approximal surface Dental deposits Biofilms on dental surfacematrixembedded microbial population, adherent to each other and/or to surface or interfaces Acquired pellicle Acellular, homogeneous anic film that forms on enamel and other hard surface by selective adsorption of salivary proteins. adsorption of salivary proteins or glycoproteins Origin Immediately after cleaning and polishing, salivary secrete deposit in the defects of enamel. ? Surface pellicle ? Subsurface pellicle Histological appearance The surface pellicle appears acellular and faintly granular under TEM Surface Pellicle Pellicles of unknown age may vary in thickness from 50~1000nm. globular fibrillar granular Different morphological types A subsurface pellicle consisting of dendritic processes that spread into the intercrystalline spaces and extend to 3181。m into the enamel. 90% water 10% solid material position According to chemical analyses amino acids account for 45% to 50% carbohydrates amount 10% to 15% of the dry weight lipid Function ?healing, repairing, or protecting the enamel surface ?imparting selective permeability to the enamel ?influencing the adherence of specific oral microanisms to the tooth surface ?serving as a substrate or nutrient for the anisms summary ? Organic deposit ? Naturally forms by selective adsorption ? Origin of protein from saliva ? After polishing, reforms rapidly ? Bacteria settle on the pellicle as soon as it forms ? formation of dental plaque Dental Plaque In the fourth century B. C. Aristotle related soft, adhere food deposits to tooth decay, but it was not until the advent of the microscope in the seventeenth century that “animalcules (microanism) were seen in these dental deposits. Anton van leeuwenhoek, a draper and sheriff`s chamberlain in Delft recognized the limitation of mechanical oral hygiene in removing these deposits. Anton Van leeuwenhoek saw large numbers of living cells in scrapings from teeth: I judge from myself that all the people living in our united Netherlands are not as many as the living animalcules that I carry in my own mouth this very day. Terminology 1847 Ficinus a slime coating denticulate 1897 Williams demonstrated the presence of a mass of microanisms 1895 . Black gelatinous microbial plaque Dental plaque Most figurative description: a bacterial aspic with millions of anisms standing shoulder to shoulder More formal definition by L?e: plaque is the soft, nonmineralized, bacterial deposit which forms on teeth and dental prosthesis that are not adequately cleaned Morphology of dental plaque A white or offwhite accumulation Variable thickness Three main typies of anisms coccoid rodshaped filamentous classification ?Supragingival plaque ?Subgingival plaque ?Dental calculus (calcified plaque) Supragingival plaque ?Smooth surface plaque ?Fissure plaque Supragingival smooth surface plaque Divided into 4 areas: ? plaque/tooth interface ? condensed microbial layer ? body of the plaque ? plaque surface plaque/tooth interface In some locations no pelicle Higher magnification of plaqueenamel border. Microanisms that divide in horizontal planes are in direct contact with enamel (1? 30,000). ? Condensed microbial layer a layer of very densely packed coccoid anisms, from 3~20 cells thick