Biofilm and Periodontal Microbiology Lecture PDF

BIOFILM AND PERIODONTAL MICROBIOLOGY Dr. Mohammed N. Zahid, BDS, H-Implant Dip, SBP OUTLINE:  INTRODUCATION The human fetus inside the uterus is sterile, but as soon as it passes through the birth canal, it acquires vaginal and fecal microorganisms. Wit...

BIOFILM AND PERIODONTAL MICROBIOLOGY Dr. Mohammed N. Zahid, BDS, H-Implant Dip, SBP OUTLINE:  INTRODUCATION The human fetus inside the uterus is sterile, but as soon as it passes through the birth canal, it acquires vaginal and fecal microorganisms. Within 2 weeks, a nearly mature microbiota is established in the gut of the newborn baby. Streptococcus salivarius and Streptococcus mitis, have been identified as the first and most dominant oral microbes to colonize the oral cavity of newborn infants. The species that colonize the teeth after eruption include Streptococcus sanguinis, Lactobacillus spp. and Streptococcus oralis. THE ORAL CAVITY FROM A MICROBE’S PERSPECTIVE  BACTERIA AND THEIR BIOFILM MODE OF LIVING Biofilms are composed of microbial cells encased within a matrix of extracellular polymeric substances, such as polysaccharides, proteins, and nucleic acids. The intercellular matrix consists of organic and inorganic materials derived from saliva, gingival crevicular fluid, and bacterial products. Organic constituents of the matrix include polysaccharides, proteins, glycoproteins, lipid material, and DNA. The inorganic components of plaque are predominantly calcium and phosphorus, with trace amounts of other minerals such as sodium, potassium, and fluoride.  BACTERIA AND THEIR BIOFILM MODE OF LIVING Supragingival plaque is found at or above the gingival margin; when in direct contact with the gingival margin, it is referred to as marginal plaque. Subgingival plaque is found below the gingival margin, between the tooth and the gingival pocket epithelium.  BACTERIA AND THEIR BIOFILM MODE OF LIVING The tooth-associated cervical plaque that adheres to the root cementum does not markedly differ from that observed in gingivitis. At this location, filamentous microorganisms dominate, but cocci and rods also occur., This plaque is dominated by gram-positive rods and cocci. The apical border of the plaque mass is separated from the junctional epithelium by a layer of host leukocytes, and the bacterial population of this apical-tooth–associated region shows an increased concentration of gram- negative rods. Techniques have been developed that allow for the specific visualization of individual bacteria within mixed populations.With these methods, specific labeling is achieved by using nucleic acid probes (fluorescence in situ hybridization [FISH]) or specific antibodies (immunofluorescence).  BACTERIA AND THEIR BIOFILM MODE OF LIVING Techniques have been developed that allow for the specific visualization of individual bacteria within mixed populations. With these methods, specific labeling is achieved by using : Nucleic acid probes (fluorescence in situ hybridization [FISH]) Specific antibodies (immunofluorescence).  BACTERIA AND THEIR BIOFILM MODE OF LIVING Accumulation of a Dental Plaque Biofilm: (1) the formation of the pellicle on the tooth surface, (2) the initial adhesion/attachment of bacteria. (3) colonization/plaque maturation.  BACTERIA AND THEIR BIOFILM MODE OF LIVING Clinically, early undisturbed plaque formation on teeth follows an exponential growth curve when measured planimetrically. During the first 24 hours when starting with a clean tooth surface, plaque growth is negligible from a clinical viewpoint.  BACTERIA AND THEIR BIOFILM MODE OF LIVING Factors That Affect Supragingival Dental Plaque Formation: 1. Topography of Supragingival Plaque 2. Surface Microroughness 3. Individual Variables That Influence Plaque Formation 4. Variation Within the Dentition 5. Impact of Gingival Inflammation and Saliva 6. Impact of Patient’s Age 7. Spontaneous Tooth Cleaning  MICROBIOLOGIC SPECIFICITY OF PERIODONTAL DISEASES Nonspecific Plaque Hypothesis This theory, which is called the nonspecific plaque hypothesis, was supported by epidemiologic studies that correlated both age and the amount of plaque with evidence of periodontitis.  MICROBIOLOGIC SPECIFICITY OF PERIODONTAL DISEASES Specific Plaque Hypothesis The pathogenicity of dental plaque depends on the presence of or an increase in specific microorganisms. This concept encapsulates that plaque that harbors specific bacterial pathogens may provoke periodontal disease because key organisms produce substances that mediate the destruction of host tissues.  MICROBIOLOGIC SPECIFICITY OF PERIODONTAL DISEASES Ecologic Plaque Hypothesis According to the ecologic plaque hypothesis, both the total amount of dental plaque and the specific microbial composition of plaque may contribute to the transition from health to disease.  MICROBIOLOGIC SPECIFICITY OF PERIODONTAL DISEASES Keystone Pathogen Hypothesis The keystone pathogen hypothesis indicates that certain low- abundance microbial pathogens can orchestrate inflammatory disease by remodeling a normally benign microbiota into a dysbiotic one.  THE TRANSITION FROM HEALTH TO DISEASE A change in the composition of a bacterial community as the result of external, nonmicrobial factors is termed: allogenic succession. Smoking is a good example of such interaction. In autogenic succession (i.e., a change in the composition of a microbial community that arises from microbial activities), interbacterial and viral–bacterial interactions are involved.  THE TRANSITION FROM HEALTH TO DISEASE When comparing the microbiota among conditions of health, gingivitis, and periodontitis, the following microbial shifts can be identified as health progresses to periodontitis: From gram-positive to gram-negative From cocci to rods (and, at a later stage, to spirochetes) From nonmotile to motile organisms From facultative anaerobes to obligate anaerobes From fermenting to proteolytic species  THE TRANSITION FROM HEALTH TO DISEASE Gingivitis: Predominant gram-positive species include Streptococcus spp. (S. sanguinis, S. mitis, S. intermedius, S. oralis, S. anginosus), Actinomyces spp. (A. oris, A. naeslundii), E. nodatum, and P. micra. Chronic Periodontitis: In patients with chronic periodontitis, the bacteria that are most often detected at high levels include P. gingivalis, T. forsythia, P. intermedia, Localized Aggressive Periodontitis: A. actinomycetemcomitans is generally accepted as the primary etiologic agent in most but not all cases of localized aggressive periodontitis.