INTRODUCTION:

Oral biofilms is a community of bacteria intimately associated with each other and included within an exopolymer matrix: this biological unit exhibits its own properties, quite different in comparison with those showed by the single species in planktonic form [1]. Oral biofilms develop under a range of different conditions and different environment. Factors that affect oral biofilm development, including inter bacterial co-adhesion, pH, oxygen and nutrients [2]

Biofilms can be formed by a single bacterial species, but biofilms more often consist of many species of bacteria, as well as fungi, algae, protozoa, debris, and corrosion products. Essentially, a biofilm may form on any surface exposed to bacteria and some amount of water.

Under certain circumstances, the microbial homeostasis can break down and diseases such as caries can occur. In dental caries, there is a shift toward increased proportions of acid – producing and acid-tolerating species, such as mutants streptococci and lactobacilli, although other species with relevant traits can participate in demineralization [3].

Control of oral biofilms is fundamental to the maintenance of oral health and to the prevention of dental caries, gingivitis, and periodontits [4]. This review is about the oral biofilms concept in micro ecology.

FORMATION OF ORAL BIOFILMS :

Formation of a biofilm begins with the attachment of free-floating microorganisms to a surface. These first colonists adhere to the surface initially through weak, reversible adhesion via van der Waals forces. If the colonists are not immediately separated from the surface, they can anchor themselves more permanently using cell adhesion structures such as pili. Hydrophobicity also plays an important role in determining the ability of bacteria to form biofilms, as those with increased hydrophobicity have reduced repulsion between the extracellular matrix and the bacterium[5].

DEVELOPMENT OF ORAL BIOFILM:

· Adsorption of Host and Bacterial Molecules to the Tooth Surface

· Passive Transport of Oral Bacteria to the Tooth Surface

· Co-Adhesion of later colonizers to already attached early colonizers

· Multiplication of the Attached Microorganisms

Adsorption of host and bacterial molecules to the tooth surface-

The first step in plaque biofilm development is the adsorption of host and bacterial molecules to the tooth surface. Within minutes of tooth eruption or a cleaning, pellicle formation begins, which can be defined as a thin coat of salivary proteins [9]. The pellicle acts like an adhesive by sticking to the tooth surface and encouraging a conditioning film of bacteria to attach to the pellicle [7]. This conditioning film directly influences the initial microbial colonization, and continues to adsorb bacteria to the tooth surface.

Passive Transport of Oral Bacteria to the Tooth Surface-

Following pellicle formation, there is passive transport of oral bacteria to the tooth surface, which involves a reversible adhesion process [8]. By using weak, long-range physicochemical interactions between the pellicle coated tooth surface and the microbial cell surface, an area of weak attraction is formed that encourages the microbes to reverse their previous adhesion to the pellicle and come off the tooth surface (hence the term "reversible adhesion") [7]. This reversible adhesion then leads to a much stronger, irreversible attachment, as short-range interactions between specific molecules on the bacterial cells and the complementary receptor proteins on the pellicle surface occur. Because many oral microbial species have multiple adhesion types on their cell surface, they can thus participate in a plethora of interactions with both other microbes and with the host surface molecules [7].

Co-Adhesion of later colonizers to already attached early colonizers-

The co-adhesion of the later colonizers to the already present biofilm continues to involve many specific interactions between bacterial receptors and adhesions. These interactions build up the biofilm to create a more diverse environment, which includes the development of unusual morphological structures like corn-cobs and rosettes [9].

Multiplication of the Attached Microorganisms-

Polymer production causes the development of the extracellular matrix, which consists of soluble and insoluble glucans, fructans, and heteropolymers [1]. This matrix is one of the key structural aspects of the plaque biofilm, much like that of other biofilms. Biofilms such as this are very thick, consisting of 100-300 cell layers. The bacterial stratification is arranged according to metabolism and aerotolerance, with the number of gram-negative cocci, rods and filaments increasing as more anaerobic bacteria appear [10]. As the biofilm thickens and becomes more mature, to further protect them from the oxygen-rich environment within the oral cavity.[9].

ORAL BIOFILMS ASSOCITATED DIESEASES:

Dental plaque is a biofilm or mass of bacteria that grows on surfaces within the mouth. It is a sticky colorless deposit at first, but when it forms tartar it is brown or pale yellow that is commonly found between the teeth, front of teeth, behind teeth, on chewing surface, along the gumline, or below the gumline cervical margins[11].

Fig :1. Formation of oral biofilms

Streptococcus pneumoniae causes Pneumococcal disease. These bacteria can cause many types of illnesses, including: pneumonia (infection of the lungs), ear infections, sinus infections, meningitis (infection of the covering around the brain and spinal cord), and bacteremia (blood stream infection). Pneumococcus bacteria are spread through coughing, sneezing, and close contact with an infected person.[12]

Periodontitis occurs when inflammation or infection of the gums (gingivitis) is allowed to progress without treatment. Infection and inflammation spreads from the gums (gingiva) to the ligaments and bone that support the teeth. Loss of support causes the teeth to become loose and eventually fall out. Periodontitis is the primary cause of tooth loss in adults. This disorder is uncommon in young children, but increases during the teen years[13].

Dental caries is bacterial breakdown of the hard tissues of the teeth (enamel, dentin and cementum). This occurs due to acid made from food debris or sugar on the tooth surface. Complications may include inflammation of the tissue around the tooth, tooth loss, and infection or abscess formation.[14].

ORAL BIOFILMS ASSOCIATED WITH SYSTEMIC HEALTH:

Atheroma-. Direct evidence for the role of dental biofilm infection in systemic inflammation comes from findings of periodontal microorganisms in human carotid atheromas. Studies of atheromatous lesions in carotid arteries revealed that over 40% of atheromas contain antigens from periodontal pathogens including P gingivalis, T forsythensis, and Prevotella intermedia. [15,16]

Respiratory Disease- Biofilm in the oral cavity may serve as a reservoir of infection leading to respiratory disease. Pseudomonas aeruginosa, Staphylococcus aureus, and enteric bacteria have been shown to colonize the teeth of patients admitted to hospitals and long-term care facilities. These bacteria may be released into saliva and aspirated into the lower airway causing respiratory infection[17-23,24]

Diabetes Mellitus- is another chronic systemic disease associated with periodontitis. In fact, periodontitis has been identified as one of the major complications of diabetes. Although diabetes increases the susceptibility to periodontal disease periodontitis may also increase the difficulty of maintaining satisfactory glycemic control in people with diabetes as compared with those with diabetes without periodontitis[25-26]

Cardiovascular disease is characterized by inflammatory plaque accumulation in blood vessels that can cause thromboses and lead to myocardial infarction. Atherosclerosis represents a chronic inflammatory process that causes endothelial dysfunction and injury to the elastic and muscular arterial tissue. Animal model studies of the relationship between cardiovascular disease and periodontal disease demonstrate that clinically induced oral infection with P gingivalis will increase atheroma size and elevate CRP levels in the blood. Conversely, some studies have shown that treatment of periodontitis decreases CRP blood levels [27].

TREATMENT PLAN FOR ORAL BIOFILM TO PROMOTE HEALTH:

Oral biofilm cannot be completely eliminated, its pathogenicity can be lessened through effective oral hygiene measures. Daily toothbrushing, interdental cleaning, and the use of topical antimicrobial chemotherapeutics are patient-based strategies to reduce the bacterial biofilm and to help prevent periodontal diseases. American Dental Association (ADA)-Accepted antimicrobial mouthrinses have been shown to help prevent and reduce plaque and gingivitis when added to a daily oral hygiene regimen of mechanical plaque removal.[28]

CONCLUSION:

Oral biofilm is three dimensional structure and is a complex, organized microbial community that is the primary etiologic factor for the most frequently occurring oral diseases, dental caries and periodontal diseases. Although the oral biofilm cannot be eliminated, it can be controlled with comprehensive mechanical and chemotherapeutic oral hygiene practices. Teaching patients to use daily brushing, interdental cleaning, and antimicrobial mouthrinses[27].

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Received on 03.06.2016 Modified on 20.06.2016

Research J. Pharm. and Tech 2016; 9(10):1812-1814.

DOI: 10.5958/0974-360X.2016.00368.1