Dental Plaque Microbiology PDF

Microbiology Unit 20 Dental Plaque Ve más allá 1 DENTAL PLAQUE • Biofilm formed by microorganisms attached to each other and to the tooth surface, embedded, interwoven and surrounded by extracellular material of a triple abiotic origin: bacterial, saliva and diet • Its composition varies with ti...

Microbiology Unit 20 Dental Plaque Ve más allá 1 DENTAL PLAQUE • Biofilm formed by microorganisms attached to each other and to the tooth surface, embedded, interwoven and surrounded by extracellular material of a triple abiotic origin: bacterial, saliva and diet • Its composition varies with time and location (continuous reorganization) DENTAL PLAQUE Bacterial plaque versus dental plaque  Viruses, fungi and protozoa have been isolated from plaque. Due to this, the term dental plaque is used since it offers the possibility of including many more microorganisms in its content.  Another name today is biofilm. Types of plaque according to location 1.- Supragingival or dentogingival plaque or smooth surfaces plaque. Plaque of the gingival margin. 2.- Subgingival plaque: plaque of the gingival sulcus or periodontal pocket in periodontitis. 3.- Root surfaces plaque SUPRAGINGIVAL OR DENTOGINGIVAL PLAQUE Plaque on the surface of the teeth (enamel), above the gum. It is greater in the dent gingival area (in the margin of the gingiva) where cleaning is less effective  Smooth surfaces plaque: On smooth surfaces such as the buccal or buccal and palatal or lingual surfaces of the teeth.  Approximal plaque: On the contact areas of teeth (interdental spaces).  Fissure plaque: On the pits, fissures and grooves on the occlusal surfaces. Subgingival plaque Plaque located below the gingival margin in the gingival sulcus, or in the course of periodontal disease in the gingival pocket (sulcus greater than 3 mm)  Subgingival plaque attached to tooth (cementum)  Plaque attached to epithelium  Floating plaque: between both of the above structures Root surface plaque Plaque on the cementum when it is exposed to the oral microenvironment (gingival recession, periodontitis)  Appears when the roots are exposed to the oral environment.  Very similar to the subgingival one attached to the tooth and to the one with smooth surfaces at the dentogingival junction Relative distribution of bacteria in the different plaques in healthy individuals Smooth surfaces Fissure Approximal Root Subgingival Oral Streptococci +++ +++ ++ +++ +++ Actinomyces spp. +++ ++ +++ +++ +++ ++ + ++ + + BG- strict anaerobes + - + +/- + BG – facultative anaerobes + - + ++ -/+ Other BG+ Facultative anaerobes + + -/+ -/+ + +/- - - - -/+ Veillonela spp. Oral Treponemas (Capnocytophaga) PLAQUE DEVELOPMENT  The plaque formation is an autogenic process.  There are changes in composition induced by microorganisms. 1 - Acquired pellicle (AP) 2 - Transport of bacteria to the AP 3 - Reversibly adhesion to the AP 4 - Primary settlement 5 - Secondary Colonization 6 - Mature plaque 7 - Mineralization phase PLAQUE DEVELOPMENT 1. Acquired pellicle  It is an insoluble, amorphous and acellular coating that can be generated naturally and spontaneously on the surface of the tooth.  It is not made up of bacteria  It is made by a selective deposition of salivary glycoproteins on the surface of the hydroxyapatitebased tooth enamel. PLAQUE DEVELOPMENT Acquired pellicle functions: a) Protective: avoids tooth decalcification, prevents the penetration of acids and the output of cations. b) Destructive: allows bacterial colonization. The microorganisms (primarily cocci) can be adhered to it. PLAQUE DEVELOPMENT 2. Transport of bacteria to acquired pellicle While the AP appears, the first bacteria arrive: • By the saliva flow • By own movements • By desquamated epithelial cells PLAQUE DEVELOPMENT 3. Reversibly adhesion to the acquired pellicle • By deposition: in fissures (structural enamel defects) • By adherence: on smooth surfaces, such as buccal surfaces • Adhesion by ionic bridges between the AP and negatively charged bacteria. Union through positive ions (calcium, hydrogen, magnesium) provided by saliva. PLAQUE DEVELOPMENT 4. Primary colonization • Irreversible adhesion between AP receptors, adhesins and fimbriae of bacteria • Pioneer bacteria are oral streptococci (viridans group and S. sanguinis, S. oralis, S. mitis) and Actinomyces naeslundii. • They multiply itself during the first 48h of acquisition of the AP • Thin plaque: aerobic metabolism PLAQUE DEVELOPMENT 5. Secondary colonization  The plaque becomes thicker and deeper areas become anaerobic.  Incorporation of new microorganisms mainly anaerobic. 6. Mature plaque  At 2-3 weeks.  Stable plaque with few variations.  Empty spaces at depth spaces (lack of O2 and nutrients), bacterial autolysis. PLAQUE DEVELOPMENT 7. Mineralization  After a certain time, very variable (days or weeks), formation of calculus or tartar  70-80% inorganic salts: hydroxyapatite, octocalcium phosphate…  The rest organic compounds: proteins, carbohydrates, lipids MATURE PLAQUE COMPOSITION • Microorganism (bacteria, viruses, fungi and protozoa) • Acellular matrix Mature plaque composition Bacteria Other microorganisms: Mycoplasma spp., Candida spp, Trichomonas tenax, Entamoeba gingivalis ... Mature plaque composition COCCI  Gram positive facultative anaerobes: oral Streptococci  Gram negative strict anaerobes: Veillonella spp.  Gram negative aerobes: Neisseria spp.  Gram positive anaerobes: Peptostreptococcus and Peptococcus Mature plaque composition BACILLI  Gram + facultative anaerobes: Actinomyces naeslundii and A. viscosus  Gram - facultative anaerobes : Eikenella spp, Capnocytophaga spp.  Gram - strict anaerobes: Fusobacterium spp, Porphyromonas spp.  Gram + strict anaerobes: Eubacterium spp, Bifidobacterium spp. Mature plaque composition In caries increases: Streptococcus mutans In periodontitis increases: • Porphyromonas gingivalis • Aggregatibacter (Actinobacillus) actinomycetemcomitans Bacterial species found in the dental plaque Facultative anaerobes Grampositive Actinomyces naeslundii Streptococcus mutans Streptococcus sanguinis Gramnegative Aggregatibacter actinomycetemcomitans Capnocytophaga spp Eikenella corrodens Spirochetes Strict anaerobs Porphyromonas gingivalis Fusobacterium nucleatum Prevotella intermedia Bacteroides forsythus Campylobacter rectus Treponema denticola Treponema spp Mature plaque composition Acellular matrix  Surrounding the microorganisms of the plaque  Nutritional intake  It comes from the microbiota, diet and saliva Mature plaque composition Acellular matrix Composition: • Inorganic compounds: K, Na, Ca and phosphates etc. Variable. • Water: ~ 70-80% • Carbohydrates: 10-30%, come from diet, saliva, cellular debris and bacteria.  Its catabolism generates acid. When the pH <4.5 to 5 demineralization occurs.  Importance for bacterial aggregation in the plaque (glucans) • Protein: 30-50%, come from diet, saliva and cell desquamation. Catabolism liberates amines that neutralizes the acidic pH (protection) • Lipids: Scarce, 20% (glycolipids, glycerides, cholesterol, etc.) Microbiologic control of plaque The most prevalent diseases in the oral cavity (caries and periodontal disease) are caused by plaque. It is important to prevent and eliminate it. Control methods  Antimicrobials  Anti-adhesive compounds  Mechanical removal Microbiological control of plaque Antimicrobials • Generally topically administrated (gels, mouthwashes, chewing gums ....) • They have to penetrate into the plaque • Specificity: they should not affect normal intestinal flora.  NO antibiotics, only if there is any involvement of the subgingival area.  YES: Antiseptics (bisbiguanides), etc. fluorides. Microbiological control of plaque Antiseptics: bisbiguanides  Chlorhexidine and others (alexidine, heptihexidina ...)  Active against GP and GN, especially against oral streptococci.  Bactericidal or bacteriostatic depending on concentration.  Anti-adhesive activity and antimicrobial performance by altering the membrane.  Use: 0.2 and 0.12%.  Does not pass through oral epithelium  Retention and slow elimination Microbiological control of plaque Fluorides  The main action is to strengthen enamel and cement  It also has anti-plaque effectiveness.  Negatively charged ions interfere with ionic bonds  It decreases intracellular pH of bacteria, by inhibition of transport pumps. Microbiological control of plaque Other agents • Activators of lactoperoxidase • Phosphates • Essential oils such as thymol and eucalyptol • Xylitol Microbiological control of plaque Mechanical removal • Suitable method • Brushing twice a day (at least) with appropriate toothpaste. • Dental floss • Removal of plaque: curettes, chisels, etc.. THANKS FOR YOUR KIND ATTENTION! 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