Periodontology Lec. 2 سهى محمد سامي حسن.د – جراحة الفم والوجه والفكين-ماجستير Etiology of periodontal diseases. The reasons why gingivitis was established or why gingivitis develops into periodontitis ? are still incompletely understood . It appears that: 1. the proliferation of pathogenic microorganism . 2. their toxic potency . 3. their capacities to invade tissues . 4. Individual host response . Gingivitis is completely reversible periodontitis is only partially reversible . Gingivitis and periodontitis is due to a multifactorial diseases . 1. pathogenic microorganisms which is the primary etiological factor for existences of Gingivitis and periodontitis . 2. heredity the genetically determined non – specific and specific immune responses as well as systemic syndromes and diseases influence the existence and the clinical course of periodontitis . 3. Habits and the patient s own approach to general health will influence plaque formation and host response , both systematically and particularly with regard to oral health . 4. Social circumstances influence the systemic and psychic well being of the patient .Problems in the socioeconomic arena lead to negative stress . 5. Psychic burdens and stress influence the immune status . Experimental gingivitis model: From day 0 on when mechanical plaque , control was stopped , plaque will slowly form on the teeth ,with the time the plaque composition changes , with a shift to more gram – negative species and more rods ,film filaments, and from day 7 on , spiriles and spirochetes from day 3 on , the first symptoms of gingival inflammation become visible . When proper plaque control is reestablished , the plaque composition returns to the initial situation ,and the symptoms of gingivitis disappear . Gram + positive microorganisms 1. streptococcus . S. anginosus S. milleri S. mutans S. sanguis S. oralis S. mitis S. intermedius 2. Acinomyces A. naeslundii A. viscosus A. odontolyticus A. israelii 3. Propionibacterium 4. Rothia R. dentocariosa. 5. Lactobacillus . L. oris L.acidophilus L. salivarius L. buccalis Gram – negative microorganisms 1. Neisseria . 2. Branchamella . 3. Actinobacillus . 4.Haemophilus . 5. Bacteroides . 6. Fusobacterium. 7. Campylobacter . Mycoplasm Spirochetes acute necrotizing ulcerative gingivitis . Candida albicans Entamoeba .