Microbiology of Periodontal Diseases PDF

Clinical criteria of normal gingiva: Color: the healthy gingiva is usually described as “coral pink” (pale pink), due to the vascular supply, the thickness, and degree of keratinization of the epithelium, and the presence of pigment- containing cells. It is correlated with...

Clinical criteria of normal gingiva: Color: the healthy gingiva is usually described as “coral pink” (pale pink), due to the vascular supply, the thickness, and degree of keratinization of the epithelium, and the presence of pigment- containing cells. It is correlated with the cutaneous pigmentation. The alveolar mucosa is red, smooth, and shiny. Physiologic pigmentation is usually found in black individuals.( due to Melanin, a non- hemoglobin-derived brown pigment). Dr. Ahmed Shawkat 1 Dr. Ahmed Shawkat 2  Form: It depends on the shape and size of interdental area, the gingival margin usually terminate against the tooth in a knife-edge fashion. The height of the interdental gingiva varies with the location of the proximal contact. the shape of interdental gingival papillae is correlated with shape of teeth and embrasures: A- Broad interdental papillae. B- Narrow interdental papillae. Dr. Ahmed Shawkat 3  Contour: The marginal gingiva envelops the teeth in collar-like fashion and follows a scalloped outline (festooned) on the facial and lingual surfaces. There are interradicular depressions and prominences corresponding to the contours of the roots. On teeth with pronounced mesiodistal convexity (e.g. maxillary canines) or teeth in labial version, the normal arc-like contour is accentuated, and the gingiva is located farther apically. On teeth in lingual version, the gingiva is horizontal and thickened. Dr. Ahmed Shawkat 4  Consistency: The gingiva is firm, resilient, and, with the exception of the movable free gingiva, tightly bound to the underlying bone. The collagenous nature of the lamina propria determine the firmness of the attached gingiva. Also, the gingival fibers contribute to the firmness of the gingival margin. Dr. Ahmed Shawkat 5  Surface texture: The gingiva presents a textured surface similar to an orange peel. The surface of dried gingiva should be matt. The attached gingiva is stippled, while marginal gingiva is not. The central portion of the interdental papillae is usually stippled, but the marginal borders are smooth. Stippling is a form of adaptive specialization or reinforcement for function. It is a feature of healthy gingiva. It is also related to the presence and degree of epithelial keratinization. Dr. Ahmed Shawkat 6 Microbiology of Periodontal Diseases Dr. Ahmed Shawkat Ass. Prof. of Periodontology and Oral Medicine Dr. Ahmed Shawkat 7 Microbiology of Periodontal Diseases As many as 500 different species of bacteria that colonize the oral cavity can affect the delicate balance of host-bacterial interactions leading to health or disease. Periodontal infection is initiated by specific invasive oral pathogens that colonize dental plaque biofilms on the tooth root surface. Local and systemic factors can also modulate an individual’s susceptibility to periodontitis. Dr. Ahmed Shawkat 8  In general, this microbiota lives in harmony with the host, but under special conditions (reduced host response, increased mass or pathogenicity) disease may occur.[most of oral bacteria are commensal and beneficial....illustrated by development of yeast infections when normal oral flora is reduced(when ?) ] The oral cavity with its microbiota is an ecologic system of great complexity. From a microbiologic viewpoint, teeth and implants are unique as they provide a hard, non- shedding surface that allows adherence of bacterial deposits. Dr. Ahmed Shawkat 9  Classification of Bacteria Morphology Cell wall characteristics Oxygen requirement for growth Bacterial metabolism Dr. Ahmed Shawkat 10  Morphotypes Several morphologic forms of bacteria exist as: - Cocci (spherical forms) - Rods (bacilli) - Spirochetes (spiral forms) Dr. Ahmed Shawkat 11 Dr. Ahmed Shawkat 12 Dr. Ahmed Shawkat 13 Dr. Ahmed Shawkat 14  Cell wall characteristics Bacteria can be divided according to gram staining into: - gram-positive. - Gram-negative. Dr. Ahmed Shawkat 15  Oxygen requirements for growth Aerobes: bacteria that require oxygen for growth. Anaerobes: bacteria that do not survive in presence of oxygen. Facultative anaerobes: bacteria that can survive in the presence or absence of oxygen. Capnophilic microorganisms: bacteria whose growth is stimulated by carbon dioxide. Dr. Ahmed Shawkat 16  Bacterial metabolism Saccharolytic microorganisms: obtain their energy from the breakdown of sugars to smaller end products. Asaccharolytic microorganisms: do not ferment sugars but can ferment amino acids and small peptides. Dr. Ahmed Shawkat 17  Oral cavity = Open system Nutrients + Microbes Removal of Bacteria ????????? 1. Flow of saliva 2. Flow of gingival fluid 3. Chewing 4. Desquamation of epithelial cells (high turn-over rate of intraoral epithelial cells) Some bacteria may be simply retained in pits and fissures or in the protected areas in-between the teeth or under the edges of dental restorations. Other organisms have specific mechanisms of adherence on tooth surfaces in the form of aggregates or plaque. Dr. Ahmed Shawkat 18  Acquisition of the oral flora An absolutely plaque-free condition in the oral cavity is unachievable or an illusion. At birth, oral cavity is sterile. Within few hours, microorganisms appear by transmission from other individuals, and those adapted to adhere to the oral mucosa such as Streptococcus salivarius. By 1 year of age, a more complex flora become established (e.g. Staphylococcus species, Streptococcus species, Actinomyces species,......etc) At puberty, marked shift in oral flora occur, and many periodontal pathogens become established. These changes may be the result of the availability of sex hormones(which can replace vitamin K requirements by some bacteria). Dr. Ahmed Shawkat 19  Criteria for identification of periodontal pathogens In 1870, Robert Koch developed the classic criteria by which a microorganism can be judged to be a causative agent in human infections (Koch’s postulates): 1- Must be routinely isolated from diseased individuals. 2- Must be grown in pure culture in the laboratory. 3- Must produce a similar disease when inoculated into susceptible laboratory animal. 4- Must be recovered from lesions in a diseased laboratory animal. e.g. Streptococcus mutans in dental caries. Dr. Ahmed Shawkat 20  In 1992, Sigmund Socransky proposed Socransky’s criteria: 1- Must be associated with disease, as evident by increase in number of organisms at diseased sites. 2- Must be eliminated or decreased in sites that demonstrate clinical resolution of disease. 3- Must demonstrate a host response. 4- Must be capable of causing disease in experimental animal models. 5- Must demonstrate virulence factors to cause destruction. Dr. Ahmed Shawkat 21 Characteristics of health-related bacteria: Gram positive. Aerobes or facultative anaerobes. Generally non-motile. Examples: Streptococcus sanguis, Streptococcus mitus, Actinomyces viscosus. ( yellow complex or purple complex of organisms) Dr. Ahmed Shawkat 22 Characteristics of disease-related bacteria: Predominantly Gram negative ( cell wall has a lipopolysaccharide base, also known as endotoxin, that has significant pathogenic potential). Strict anaerobes. Non-motile and motile forms. Examples: Aggregatibacter actinomycetemcomitans, Prevotella intermedia. (orange or red complex of organisms) Dr. Ahmed Shawkat 23 Dr. Ahmed Shawkat 24 THANK YOU Dr. Ahmed Shawkat 25