Dental Plaque: Biofilm Concept PDF

Dental Plaque The concept of Biofilm By: Nagham khoury  Introduction The human fetus inside the uterus is sterile, but as soon as it passes through the birth canal, it acquiers vaginal and fecal microorganisms. Within 2 weeks, anearly mature microbiota is...

Dental Plaque The concept of Biofilm By: Nagham khoury  Introduction The human fetus inside the uterus is sterile, but as soon as it passes through the birth canal, it acquiers vaginal and fecal microorganisms. Within 2 weeks, anearly mature microbiota is established in the gut of the newborn. After weaning (>2 years), the entire human microbiota is formed and comprises a very complex collection of hundreds of different types of bacteria with approximately 10^14 microbial cells. From this moment on, our body contains 1.3 to 10 times more bacteria than human cells. It has been estimated that, for a normal, healthy human being, the bacterial population comprises 2 kg of the total body weight.  The colonization of the oral cavity also starts close to the time of birth. Within hours after birth, the sterile oral cavity is colonized by low numbers of mainly facultative and aerobic bacteria. At that time, the oral microbiota of newborns closely resembles the mothers vaginal microbiota or for newborns delivered by cesarean section, the mothers skin microbiota. From the second day, anaerobic bacteria can be detected in the infants edentulous mouth.  The number of oral bacteria increases gradually as a result of exposure to external environmental microbial sources  The ability of a bacterium to adhere to its host is crucial for the induction of infectious diseases, such as gingivitis or periodontitis.  Oral bacteria and especially pathogenic bacteria, such as Porphyromonas gingivalis (PG) and Aggregatibacter actinomycetemcomitans (Aa) have a large battery of virulence factors, one of which is the ability to adhere to hard intra- oral surfaces and/or to the oral mucosae.  On the basis of physical and morphologic criteria, the oral cavity can be divided into six major ecosystems (also called niches), each with the following distinct ecologic determinants: 1. The intraoral and supragingival hard surfaces (teeth, implants, restorations, and prostheses). 2. Subgingival regions adjacent to a hard surface, including the periodontal/peri-implant pocket (characterized by the presence of crevicular fluid, the root cementum or implant surface, and the pocket epithelium). 3. The buccal palatal epithelium and the epithelium of the floor of the mouth. 4. The dorsum of the tongue 5. The tonsils 6. The saliva What is a Biofilm?  Biofilms are biological structures composed of microbial cells encased within a matrix of extracellular polymeric substances, such as polysaccharides, proteins, and nucleic acids.  Variations in biofilm structure exist within individual biofilms, between different types of biofilms, and between individuals. Biofilms frequently contain micro-colonies of bacterial cells. Water channels are commonly found in biofilms, and these can form a primitive circulatory system that removes waste products and brings fresh nutrients to the deeper layers of the film.  Dental plaque is defined clinically as a structured, Dental plaque resilient, yellow-grayish substance that adheres firmly to the intraoral hard surfaces, including removable and fixed restorations. The tough extracellular matrix makes it impossible to remove plaque by rinsing or with the use of sprays. Plaque can thus be differentiated from other deposits that may be found on the tooth surface, such as materia alba and calculus.  Materia alba refers to soft accumulations of bacteria, food matter, and tissue cells that lack the organized structure of dental plaque and that are easily displaced with a water spray. Calculus is a hard deposit that forms via the mineralization of dental plaque and that is generally covered by a layer of non-mineralized plaque.  Composition of dental plaque Dental plaque is composed primarily of microorganisms. One gram of plaque contains approximately 10^11 bacteria. The number of bacteria in supragingival plaque on a single tooth surface can exceed 10^9 cells. In a periodontal pocket, counts can range from 10^3 bacteria in a healthy crevice to more than 10^8 bacteria in a deep pocket.  Composition of dental plaque The intercellular matrix of dental plaque consists of organic and inorganic materials derived from saliva, gingival crevicular fluid, and bacterial products. Organic constituents of the matrix include polysaccharides, proteins, glycoproteins, lipid material, and DNA. The organic components of plaque are predominantly calcium and phosphorus, with trace amounts of other minerals such as sodium, potassium, and fluoride. The source of inorganic constituents of supragingival plaque is primarily saliva, and the inorganic components of subgingival plaque are derived from crevicular fluid (a serum transudate). As the mineral content increases, the plaque mass becomes calcified to form calculus.  Calculus is frequently found in areas of the dentition adjacent to salivary ducts (e.g., the lingual surface of the mandibular incisors and canines, the buccal surface of Calculus the maxillary first molars), and this reflects the high concentration of minerals available from saliva in those regions. The calcification of subgingival plaque also results in calculus formation. Subgingival calculus is typically dark green or dark brown, which probably reflects the presence of blood products that are associated with subgingival hemorrhage.  Dental plaque is broadly classified as supragingival or subgingival on the basis of its position on the tooth surface toward the gingival margin. Supragingival plaque is found at or above the gingival margin; when in direct contact with the gingival margin, it is referred to as marginal plaque. Subgingival plaque is found below the gingival margin, between the tooth and the gingival pocket epithelium. In general, the subgingival microbiota differs in composition from the supragingival plaque, primarily because of the local availability of blood products and the anaerobic environment. The process of plaque formation can be divided into several phases: 1. the formation of the pellicle on the tooth surface. 2. The initial adhesion/attachment of bacteria. 3. colonization/plaque maturation.  All surfaces in the oral cavity, including the hard and soft tissues, are coated with a layer of organic material known as the acquired pellicle. The pellicle on tooth surfaces consists of more than 180 peptides, proteins, glycoproteins, and other molecules that can function as adhesion sites (receptors) for bacteria. The salivary pellicle can be detected on clean enamel surfaces within 1 minute after their introduction into the mouths of volunteers. By 2 hours, the pellicle is essentially in equilibrium between adsorption and detachment. Dental enamel is permanently covered with an acquired pellicle from the moment that teeth erupt.  The primary colonizing bacteria adhered to the tooth surface provide new receptors for attachment by other bacteria as part of a process known as co-adhesion. Together with the growth of adherent microorganisms, co- adhesion leads to the development of micro- colonies and eventually to a mature biofilm.  Plaque control 1. Microbial plaque biofilm control, also referred to as periodontal self-care, is an effective way of treating and preventing gingivitis and is an essential part of all procedures involved in the treatment and prevention of periodontal diseases. 2. It is a critical element in the long-term success of all periodontal and dental treatment. Methods for plaque biofilm control 1. The Toothbrush. 2. Powered Toothbrushes. 3. Dentifrices. 4. Interdental Cleaning Aids. 5. Gingival Massage. 6. Oral Irrigation. 7. Caries Control. 8. Chemical Plaque Biofilm Control With Oral Rinses. 9. Disclosing Agents.