Dental Microbiology

What is it about?

The mouth consists of a number of ecological niches which are colonized by a characteristic mixture of microorganisms. The main ecological areas are: the mucosa of lips, cheeks and palate; the tongue; the tooth surfaces , saliva, the tonsillar area ,and dentures, if present Main organisms as oral commensals - Streptococcus are gram-positive cocci and mainly cause dental plaque/infective endocarditis dental caries and aphthousulceration.They are found on tongue, cheek tooth surface and palate.Themutans group comprise S.mutans, S.sobrinus, S.ratti,andS.crecetti. Arachniaarethe gram-positive pleomorphic bacilli and Eubacterium are pleomorphic gram-positive rods or filaments found in dental plaque/carious dentin or necrotic dental pulp. Lactobacillus are Gram-positive bacilli, catalase-negative bacilli are found in dental plaque in small numbers/Extension of dental caries Actinomyces are gram-positive non-motile bacilli and filaments seen in dental plaque and tonsillar cryptsand dental calculus formation. Eubacterium, Anaerobic Streptococcus, Proprionbacterium, Micrococcus Staphylococcus, Veillonella, Haemophilus, Eikenella, Capnocytophaga, Fusobacteria, Leptotrichia, Bacteroides, Treponema and Entamoeba are also found in dental plaque. The establishment, survival and persistence of microbial flora are determined by: Microbial factors like adherence, production of anti microbial agents, sensitivity to antimicrobial agents, metabolic capability and nuutritional requirements. Host factors like anatomical ,area saliva , crevicular fluid, diet, oral hygiene, oral and systemic disease and oral ral immune defenses. Dental plaque is the firm microbial deposit attached on hard surfaces within mouth, consisting of microbial cells with their products along with host compounds which are mainly derived from saliva or crevicular exudates. Plaque consists of proliferating microorganisms along with epithelial cells, leukocytes and macrophages in an adherent intercellular matrix. The pioneer species or first invading bacteria are usually streptococci, especially strep. salivarius. The oral flora of most children by one year contains streptococci, staphylococci, neisseria and veillonella, with the majority also possessing actinomyces, lactobacilli, and fusobacteria. The microorganisms which colonize the dental hard tissues appear usually when teeth have erupted, e.g. strep sanguis. strep mutans. Tooth eruption results in the shift to anaerobic flora, e.g. anaerobic streptococci and motile Gram-negative rods Dental plaque can be supragingival, subgingival and denture-related. Different stages of formation of plaque include: pellicle formation , transport and adherence of pioneering organisms, coaggregation and multiplication and seeding. Dental caries can be defined as the localized destruction of the tissues of the tooth by bacterial fermentation of dietary carbohydrates. Chemicoparasitic theory put forth by Miller suggested that oral bacteria converted dietary carbohydrates into acid whichsolubilizes the hard tissue.. Smooth surfaces caries as well as pit and fissures are mainly caused by Mutanstreptococci. The Etiology of caries consist of – Host, substrate, microorganism and the time. Most important bacteria involved in caries include streptococcus mutans. Others are lactobacilli, actinomyces, veillonella. Plaque hypothesis are commonly known as specific plaque hupothesis and non specific plaque hypothesis. Periodontal diseases can be plaque-associated and non-plaque associated. The plaque associated is gingivitis and periodontitis which can further be acute and chronic. Chronic gingivitis is a non specific ,reversible inflammatory response to dental plaque involving the gingival margins. Chronic form of advanced periodontal disease is a major cause of tooth loss. NUG also termed as Vincents disease/trench mouth is a severe form of necrotizing inflammation of interdental papillae, accompanied by spontaneous gingival bleeding and pain. It is characterized clinically by a grey pseudomembrane formation. The invading microbes resembles that of spirochaetal complex. Aggressive Periodontitis is an Uncommon condition usually occurs in adolescents. Strepmilleri is commonly isolated from endodontic infections, while black pigmented bacteroides, are the predominant anaerobic Gram-negative bacilli e.g. B. endodontalisand the B.gingivalis. Endodontic infections are usually polymicrobial facultative Gram-positive cocci, mainly strep. salivarius, strep mutans. Some other common infections of the oral cavity are dry socket, Ludwigs Angina, Cellulitis, Tuberculous Osteomyelitis, PeriImplantitis, PeriCoronitis and Angular Cheilitis, candidiasis, herpetic ulcers, Herpes Labialis Erythema Multiforme, Bullous Pemphigoid and papilloma

Featured Image

Photo by masakazu sasaki on Unsplash

Photo by masakazu sasaki on Unsplash

Why is it important?

To understand the oral microbiology and to combat various oral and dental diseases.