Pathogenesis of Periodontal Disease 1 Workbook PDF

Pathogenesis of Periodontal Disease 1 Student name: Answers This workbook is to be used in conjunction with your session on the subject of Pathogenesis of Periodontal Disease.  The premise of this session is for you to complete the tasks in a self-directed way  There are links to d...

Pathogenesis of Periodontal Disease 1 Student name: Answers This workbook is to be used in conjunction with your session on the subject of Pathogenesis of Periodontal Disease.  The premise of this session is for you to complete the tasks in a self-directed way  There are links to documents/resources which will enable you to gain knowledge of this subject and to complete the tasks as you proceed  It is important that you complete and have your notes in preparation for the next session Pathogenesis of Periodontal Disease 2 in order that you have underpinning knowledge of the subject.  Please complete prior to self-checking your responses and self-assessing your knowledge of this subject. Resources: Review lectures of: Development of oral mucosa, junctional epithelium, immunology, dental plaque biofilm, virulence factor, Periodontal Disease-Microbiology ‘Host Defences’ pdf You will need to complete the workbook to meet the intended learning outcomes: By the end of this session, you should be able to:  Define periodontitis  Recall the development and role of plaque biofilm in periodontal disease  Review the tissues of the periodontium  List at least 3 types bacteria thought to be associated in the pathogenesis of periodontal disease and review the virulence factors deployed in the process  Outline the host defence in the oral cavity, with reference to the innate and acquired immune responses  Describe the functions of cytokines, prostaglandins and matrix metalloproteinases (MMPs) in the host response  Describe the basic factors which may contribute to the initiation of periodontitis  Periodontitis 1. Define the term periodontitis: Periodontitis is an microbial infection that triggers a host-mediated inflammatory response within the periodontium, leading to progressive and irreversible destruction of the periodontal ligament and supporting alveolar bone. Development and role of plaque biofilm in periodontal disease 2. Define the term plaque biofilm Plaque biofilm is an organised community of microorganisms embedded in an extracellular glycocalyx (slime layer) which build up on natural and restored solid surfaces in the oral cavity. 3. Composition of dental plaque biofilm: Intra-cellular Matrix Organic Polysaccharides Proteins Glycoproteins Lipids Inorganic (sources between supra & sub) Calcium Sodium Phosphorous Potassium 4. Complete the four stages of dental plaque biofilm formation: 1. Initial attachment of bacteria to pellicle 2. Initial colonisation of the tooth surface – new bacteria join 3. Secondary colonisation: Extracellular slime layer formation 4. Mature biofilm – mushroom shaped colonies  Tissues of the periodontium 5. Name the three distinct parts of the gingival epithelium with a description of where they are found. a) Oral epithelium-covering the free and attached gingivae b) Sulcular epithelium-lines the sulcus c) Junctional epithelium-at the base of the sulcus 6. Label the tissues of the periodontium: A- Gingivae B-Periodontal ligament C-Root cementum D- alveolar bone A B C D  Bacteria associated in the pathogenesis of periodontal disease and their virulence factors 7. The subgingival environment supports mainly anaerobic bacteria. True False 8. Name at least 3 bacteria species found to be associated with periodontal disease  Porphyromonas gingivalis  Aggregatibacter actinomycetemcomitans  Treponema denticola  Tannerella forsythia  Fusobacterium nucleatum  Prevotella intermedia 9. Note some of the virulence factors of named bacteria which enable them to colonise, invade and damage the periodontium P. gingivalis: Carbohydrate capsule- resists some host defences Produces gingipains to enable the bacterium to use GCF as a source of nutrients LPS (Lipopolysaccharide) Haemagglutinins & platelet aggregators Fimbrae and tissue invasion. Can suppress the early PMN (polymorphonuclear leukocytes) response Tannerella Forsythia: proteases and apoptotic-inducing factor Treponema denticola: Adherence factors can bind to fibroblasts Motile and can invade tissue Disruption of host defences by inducing and degrading cytokines May delay wound healing by inhibiting migration of PMNs A actinomycetemcomitans: Leukotoxin (can kill WBC, so disrupts the host defences) Other toxins can destroy fibroblasts and epithelial cells. Also produces proteases, including collagenase Can invade host epithelial cells Host defences in the oral cavity, innate and acquired immune responses 10. Which type of immune response will be initiated by plaque in the first instance? Innate immune response a) What are the key components of this immune response? Saliva, Epithelium, Inflammatory response b) Complete the table: Host defence Role in defence Inflammatory a) What is the fluid component, when does it form and what response is it’s function at this stage? GCF, forms as a result of acute inflammation; dilutes and washes out MO’s from sulcus; increases further in response to more inflammation (flow rate corresponds to degree of inflammation). Contains inflammatory mediators and antibacterial agents (complement/antibody/breakdown products) b) Which cells are mainly involved in the cellular response at this stage and what is their role? Cellular response is first line of defence; PMNs - phagocytes such as neutrophils and macrophages directly attack and remove invading MO’s. Epithelium a) How does the epithelium defend against plaque microorganisms? Creates an intact physical barrier against plaque MO’s. Epithelial cells tightly attached to each other; keratinisation; presence of a permeable barrier. b) How and when is the protective function of epithelium compromised? The junctional epithelium transforms into pocket- lining epithelium which has micro ulcerations and structure which is liable to leaking, therefore compromising the protective function c) Which cells of the junctional epithelium secrete cytokines and Tumour Necrosis Factor during the initiation of the inflammatory response in the gingival tissues? Keratinocytes d) What is the name of the tissue macrophages which are responsible for releasing host defences? Langerhans’ cells Saliva What is the role of saliva? Prevents drying of oral tissues. Antimicrobial effects – swallowing bacteria, secretion of salivary IgA- influences bacterial attachment- more likely to be swallowed. Peroxidase, lysosome and lactoferrin- mainly affect gram positive bacteria in saliva (supragingival role mainly) 11. Fill the blanks using the available words below. The adaptive immune response is also known as the acquired or specific immune response and it is activated when innate immunity is ineffective in eliminating pathogens and infection becomes established. It is highly specific to a particular pathogen by recognising it’s antigen due to immunological memory. Adaptive immunity uses two main mechanisms, known as humoral immunity (antibody response) and cell mediated immunity. antigen humoral antibody acquired cell-mediated memory specific pathogens  a) Humoral Immune response is when antibodies are produced against agents existing in the humours (extra-cellularly). Complete the table which relates to the humoral immune response: Mode Function Epithelial Langerhans’ cells Present antigenic parts from pathogens and present to circulating lymphocytes which stimulates clonal expansion after recognising the specific antigen B-cell lymphocytes Differentiate into plasma cells which then release antibody against the specific antigen Antibody IgG and IgA Production is thought to be protective Locally or systemically produced antibody To clump and prevent adherence of microorganisms to epithelium; work with complement to lyse bacteria; work with neutrophils for opsonisation (marking) and phagocytosis b) Cell-mediated response does not require the use of antibodies- uses it’s own T-Cell receptor. Antigen presentation via Langerhans’/dendritic cells TH cells: to T-Cell  produce cytokines  assist B cell differentiation into plasma cells  activate neutrophils and macrophages Progression from gingivitis to periodontitis elicits a T-cells have immunoregulatory role shift from T-cell to B-cell lesions Cytokines, prostaglandins and matrix metalloproteinases (MMPs) in the host response 12. There are several types of chemical mediators involved in periodontal disease. They are chemical messengers which link and regulate the inflammatory response, the immune response and tissue damage. Research where they are released from and complete the following table: Mediator type Action/function in periodontitis Cytokines e.g. Pro- What are cytokines? Small proteins which are crucial in inflammatory IL-1, IL-6 and controlling the growth and activity of other immune system TNF-α cells and blood cells. They signal the immune system to and aid Anti-inflammatory IL-4 and IL- in the inflammatory responses in various ways. 10 Action of cytokines in periodontitis: During periodontitis, pro- inflammatory cytokines are released in response to the pathogens which contributes to further destruction of the periodontal tissues Prostaglandins e.g. PGE_2 Bone resorption, neutrophil chemotaxis, vascular permeability and dilation Matrix metalloproteinases Pro-inflammatory- degrade connective tissue (MMPs) Factors contributing to the initiation of periodontitis 13. In health and in stable gingivitis, there is a dynamic equilibrium between dental plaque and the host defences. This equilibrium is disturbed in periodontitis which tips in favour of tissue damage. Describe what these factors are (refer to Periodontal disease- Microbiology session):  An increased amount of plaque  Increase in pathogenicity of the micro-organisms in the biofilm  Compromised host defence 14. For each of the following theories on the role of bacteria in periodontal disease, give an outline of the hypothesis, identify any issues and/or support for them. a) Non-specific Plaque Hypothesis b) Specific Plaque Hypothesis c) Keystone Pathogen- Host Response Hypothesis a) Non-specific Plaque Hypothesis -Theory proposed that stagnation of plaque biofilm and numbers of bacteria within would lead to inflammation in the adjacent gingival sulcus leading to periodontium tissue destruction Issues: Simplistic theory; most gingivitis cases do not progress to PD; patients with light traces of biofilm may suffer from PD; some sites affected, others not. b) Specific Plaque Hypothesis- Proposes that as periodontal disease develops that there is a shift in microbial composition rather than amount which determines the development of the disease Issues: Red complex (thought to be most pathogenic) can be seen in stable periodontal sites; questions arise as to whether pathogens are single causative factor; recent research recognises further species not found in red complex zone may be more causative, therefore concept of specific types as previously thought is less certain; Gram positive bacteria found in large amounts in periodontal pockets c) Keystone Pathogen-Host Response Hypothesis- theorises that specific bacterial species is key in shift from symbiotic microbes – dysbiotic microbes in biofilm colonies. This community triggers the uncontrolled host response= periodontal destruction. Previous research could not provide solid evidence to show that specific bacteria are the direct cause of periodontal destruction. Current evidence demonstrates that the immune response and uncontrolled host inflammatory response cause the tissue destruction found in periodontal disease.