Aggregatibacter actinomycetemcomitans: A species of Gram-negative, facultatively anaerobic spherical or rod-shaped bacteria indigenous to dental surfaces. It is associated with PERIODONTITIS; BACTERIAL ENDOCARDITIS; and ACTINOMYCOSIS.Pasteurellaceae: A family of coccoid to rod-shaped nonsporeforming, gram-negative, nonmotile, facultatively anaerobic bacteria that includes the genera ACTINOBACILLUS; HAEMOPHILUS; MANNHEIMIA; and PASTEURELLA.Pasteurellaceae Infections: Infections with bacteria of the family PASTEURELLACEAE.Actinobacillus Infections: Infections with bacteria of the genus ACTINOBACILLUS.Aggressive Periodontitis: Inflammation and loss of PERIODONTIUM that is characterized by rapid attachment loss and bone destruction in the presence of little local factors such as DENTAL PLAQUE and DENTAL CALCULUS. This highly destructive form of periodontitis often occurs in young people and was called early-onset periodontitis, but this disease also appears in old people.Actinobacillus: A genus of PASTEURELLACEAE described as gram-negative, nonsporeforming, nonmotile, facultative anaerobes. Most members are found both as pathogens and commensal organisms in the respiratory, alimentary, and genital tracts of animals.Exotoxins: Toxins produced, especially by bacterial or fungal cells, and released into the culture medium or environment.Periodontitis: Inflammation and loss of connective tissues supporting or surrounding the teeth. This may involve any part of the PERIODONTIUM. Periodontitis is currently classified by disease progression (CHRONIC PERIODONTITIS; AGGRESSIVE PERIODONTITIS) instead of age of onset. (From 1999 International Workshop for a Classification of Periodontal Diseases and Conditions, American Academy of Periodontology)Chronic Periodontitis: Chronic inflammation and loss of PERIODONTIUM that is associated with the amount of DENTAL PLAQUE or DENTAL CALCULUS present. Chronic periodontitis occurs mostly in adults and was called adult periodontitis, but this disease can appear in young people.Gingiva: Oral tissue surrounding and attached to TEETH.Campylobacter rectus: A species of CAMPYLOBACTER isolated from cases of human PERIODONTITIS. It is a microaerophile, capable of respiring with OXYGEN.Periodontal Pocket: An abnormal extension of a gingival sulcus accompanied by the apical migration of the epithelial attachment and bone resorption.Periodontal Diseases: Pathological processes involving the PERIODONTIUM including the gum (GINGIVA), the alveolar bone (ALVEOLAR PROCESS), the DENTAL CEMENTUM, and the PERIODONTAL LIGAMENT.Dental Plaque: A film that attaches to teeth, often causing DENTAL CARIES and GINGIVITIS. It is composed of MUCINS, secreted from salivary glands, and microorganisms.Gingival Hemorrhage: The flowing of blood from the marginal gingival area, particularly the sulcus, seen in such conditions as GINGIVITIS, marginal PERIODONTITIS, injury, and ASCORBIC ACID DEFICIENCY.Treponema denticola: A species of bacteria in the family SPIROCHAETACEAE, frequently isolated from periodontal pockets (PERIODONTAL POCKET).Fusobacterium nucleatum: A species of gram-negative, anaerobic, rod-shaped bacteria isolated from the gingival margin and sulcus and from infections of the upper respiratory tract and pleural cavity.Prevotella intermedia: A species of gram-negative, anaerobic, rod-shaped bacteria originally classified within the BACTEROIDES genus. This bacterium is a common commensal in the gingival crevice and is often isolated from cases of gingivitis and other purulent lesions related to the mouth.Porphyromonas gingivalis: A species of gram-negative, anaerobic, rod-shaped bacteria originally classified within the BACTEROIDES genus. This bacterium produces a cell-bound, oxygen-sensitive collagenase and is isolated from the human mouth.Dental Devices, Home Care: Devices used in the home by persons to maintain dental and periodontal health. The devices include toothbrushes, dental flosses, water irrigators, gingival stimulators, etc.Bacterial Load: Measurable quantity of bacteria in an object, organism, or organism compartment.Biofilms: Encrustations, formed from microbes (bacteria, algae, fungi, plankton, or protozoa) embedding in extracellular polymers, that adhere to surfaces such as teeth (DENTAL DEPOSITS); PROSTHESES AND IMPLANTS; and catheters. Biofilms are prevented from forming by treating surfaces with DENTIFRICES; DISINFECTANTS; ANTI-INFECTIVE AGENTS; and antifouling agents.Periodontium: The structures surrounding and supporting the tooth. Periodontium includes the gum (GINGIVA), the alveolar bone (ALVEOLAR PROCESS), the DENTAL CEMENTUM, and the PERIODONTAL LIGAMENT.Peri-Implantitis: An inflammatory process with loss of supporting bone in the tissues surrounding functioning DENTAL IMPLANTS.Alveolar Bone Loss: Resorption or wasting of the tooth-supporting bone (ALVEOLAR PROCESS) in the MAXILLA or MANDIBLE.Gingivitis: Inflammation of gum tissue (GINGIVA) without loss of connective tissue.Aggregatibacter: A genus of PASTEURELLACEAE. Members are nonmotile, Gram-negative, facultatively anaerobic rods or coccobacilli. Its members are X factor (HEMIN) independent and variably dependent on V factor (NAD).Bacterial Toxins: Toxic substances formed in or elaborated by bacteria; they are usually proteins with high molecular weight and antigenicity; some are used as antibiotics and some to skin test for the presence of or susceptibility to certain diseases.Streptococcus gordonii: A species of gram-positive, facultatively anaerobic bacteria in the family STREPTOCOCCACEAE. It is a normal inhabitant of the human oral cavity, and causes DENTAL PLAQUE and ENDOCARDITIS. It is being investigated as a vehicle for vaccine delivery.Periodontal Index: A numerical rating scale for classifying the periodontal status of a person or population with a single figure which takes into consideration prevalence as well as severity of the condition. It is based upon probe measurement of periodontal pockets and on gingival tissue status.Dental Plaque Index: An index which scores the degree of dental plaque accumulation.Adhesins, Bacterial: Cell-surface components or appendages of bacteria that facilitate adhesion (BACTERIAL ADHESION) to other cells or to inanimate surfaces. Most fimbriae (FIMBRIAE, BACTERIAL) of gram-negative bacteria function as adhesins, but in many cases it is a minor subunit protein at the tip of the fimbriae that is the actual adhesin. In gram-positive bacteria, a protein or polysaccharide surface layer serves as the specific adhesin. What is sometimes called polymeric adhesin (BIOFILMS) is distinct from protein adhesin.Aggregatibacter segnis: A species of Gram-negative, facultatively anaerobic pleomorphic rod-shaped often filamentous bacteria in the genus of AGGREGATIBACTER found in the oral cavity. It is associated with DENTAL PLAQUE; and BACTERIAL ENDOCARDITIS.Mouth: The oval-shaped oral cavity located at the apex of the digestive tract and consisting of two parts: the vestibule and the oral cavity proper.Gingival Crevicular Fluid: A fluid occurring in minute amounts in the gingival crevice, believed by some authorities to be an inflammatory exudate and by others to cleanse material from the crevice, containing sticky plasma proteins which improve adhesions of the epithelial attachment, have antimicrobial properties, and exert antibody activity. (From Jablonski, Illustrated Dictionary of Dentistry, 1982)Periodontal Attachment Loss: Loss or destruction of periodontal tissue caused by periodontitis or other destructive periodontal diseases or by injury during instrumentation. Attachment refers to the periodontal ligament which attaches to the alveolar bone. It has been hypothesized that treatment of the underlying periodontal disease and the seeding of periodontal ligament cells enable the creating of new attachment.Aggregatibacter aphrophilus: A species of Gram-negative, facultatively anaerobic spherical or rod-shaped bacteria indigenous to oral cavity and pharynx. It is associated with BACTERIAL ENDOCARDITIS; and MENINGITIS.Bacterial Adhesion: Physicochemical property of fimbriated (FIMBRIAE, BACTERIAL) and non-fimbriated bacteria of attaching to cells, tissue, and nonbiological surfaces. It is a factor in bacterial colonization and pathogenicity.Bacteroides: A genus of gram-negative, anaerobic, rod-shaped bacteria. Its organisms are normal inhabitants of the oral, respiratory, intestinal, and urogenital cavities of humans, animals, and insects. Some species may be pathogenic.Bacterial Proteins: Proteins found in any species of bacterium.Gene Expression Regulation, Bacterial: Any of the processes by which cytoplasmic or intercellular factors influence the differential control of gene action in bacteria.Haemophilus: A genus of PASTEURELLACEAE that consists of several species occurring in animals and humans. Its organisms are described as gram-negative, facultatively anaerobic, coccobacillus or rod-shaped, and nonmotile.Virulence Factors: Those components of an organism that determine its capacity to cause disease but are not required for its viability per se. Two classes have been characterized: TOXINS, BIOLOGICAL and surface adhesion molecules that effect the ability of the microorganism to invade and colonize a host. (From Davis et al., Microbiology, 4th ed. p486)Gram-Negative Bacteria: Bacteria which lose crystal violet stain but are stained pink when treated by Gram's method.Genome, Bacterial: The genetic complement of a BACTERIA as represented in its DNA.DNA, Bacterial: Deoxyribonucleic acid that makes up the genetic material of bacteria.Epithelial Cells: Cells that line the inner and outer surfaces of the body by forming cellular layers (EPITHELIUM) or masses. Epithelial cells lining the SKIN; the MOUTH; the NOSE; and the ANAL CANAL derive from ectoderm; those lining the RESPIRATORY SYSTEM and the DIGESTIVE SYSTEM derive from endoderm; others (CARDIOVASCULAR SYSTEM and LYMPHATIC SYSTEM) derive from mesoderm. Epithelial cells can be classified mainly by cell shape and function into squamous, glandular and transitional epithelial cells.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Polymerase Chain Reaction: In vitro method for producing large amounts of specific DNA or RNA fragments of defined length and sequence from small amounts of short oligonucleotide flanking sequences (primers). The essential steps include thermal denaturation of the double-stranded target molecules, annealing of the primers to their complementary sequences, and extension of the annealed primers by enzymatic synthesis with DNA polymerase. The reaction is efficient, specific, and extremely sensitive. Uses for the reaction include disease diagnosis, detection of difficult-to-isolate pathogens, mutation analysis, genetic testing, DNA sequencing, and analyzing evolutionary relationships.Haemophilus somnus: A species of gram-negative bacteria (currently incertae sedis) causing multisystem disease in CATTLE.Anti-Bacterial Agents: Substances that reduce the growth or reproduction of BACTERIA.Cardiobacterium: A genus of gram-negative, facultatively anaerobic bacteria in the family CARDIOBACTERIACEAE. It is found in the nasal flora of humans and causes ENDOCARDITIS.