BIOFILM
INTRODUCTION :
Free-floating bacteria in the oral cavity are called planktonic; however, they can organize themselves within a microbial community to increase their chances of survival.
1-DEFINITIONS OF BIOFILM
*According to LOE in 1963: It is a soft, non-calcified, bacterial deposit that forms on insufficiently cleaned teeth.
*According to FRANK in 1969: It is an extremely polymorphic microbial jungle made of aerobic and anaerobic bacteria, linked by an extracellular matrix attached to the surface of the tooth by the acquired pellicle, as well as desquamated epithelial cells, polymorphonuclear cells and leukocytes.
It can remain soft for a long time, it varies from one individual to another and from one place to another in the same mouth.
*According to GLICKMAN in 1972: It is a granular, soft, amorphous deposit which accumulates on the surfaces of teeth, on dental restorations and on tartar, it can only be detached by mechanical cleaning.
*According to LINDHE in 1983: It is a white, soft material, consisting of bacterial aggregates, leukocytes and desquamated epithelial cells which develop on the surface of teeth or other solid oral structures.
*HALL-STODLEY et al 2004: Biofilms are not simply a passive collection of cells adhering to a surface, but are complex, structured and dynamic biological systems.
2. FORMATION OF DENTAL BIOFILM
It begins with the formation of the acquired film, then its colonization by bacterial germs and finally its maturation.
2.1. Formation of exogenous acquired film (EAP) :
It forms spontaneously on the mineralized dental surface by the selective adsorption of salivary proteins. The main constituents of PAE are glycoproteins and phosphoproteins. PAE can be beneficial to dental health or contribute to its imbalance. Protective, it opposes the decalcification of the tooth, particularly during the ingestion of acidic foods or drinks.
2.2. Bacterial adhesion and colonization:
Adhesion is a primary ecological determinant for oral bacteria to persist and survive. Attachment of pioneer bacteria is the initial step in dental biofilm formation. These bacteria have adhesins on their surface that specifically recognize PAE receptors. Mitis group streptococci are the pioneer organisms. This adhesion results from nonspecific physicochemical interactions between the bacteria and surfaces (reversible phase). Irreversible adhesion involves nonselective and selective interactions, the first being established between a globally negatively charged bacterial surface and PAE. The second involves specific interactions between bacterial adhesins “lectins” and host receptors.
2.3. Maturation of the biofilm:
Pioneer bacteria are able to withstand high O₂ concentrations and the various elimination mechanisms of the oral cavity. Their growth allows the adhesion of other bacterial species that were unable to attach to the PAE. This is a secondary colonization.
As the number of layers increases, new environmental conditions appear, the oxygen level decreases and anaerobic bacteria develop. After several hours, new species attach to the established bacteria and thus increase the diversity of the young dental biofilm. These bacterial species “secondary or late colonizers”, appear mainly in the Gram-negative genera: Fusobacterium, Porphyromonas, Veillonella, Prevotella, Treponema.
When dental biofilm is not eliminated, the community becomes increasingly complex. Equilibrium is reached within 2 to 3 weeks. At this stage, dental biofilm can contain up to 10⁹ bacteria per mg of material. The growth of the biofilm constitutes the maturation stage.
3. THE COMPOSITION OF DENTAL BIOFILM
The biofilm consists of an extracellular matrix and bacteria.
3.1. The extracellular matrix which results in the synthesis of extracellular membrane “ECM”. This matrix allows the aggregation of secondary colonizing bacteria and the cohesion of the biofilm. The inter-bacterial substance is composed of salivary glycoproteins, lysed bacteria and bacterial ECM.
The MEC is composed of 25% aqueous phase but also saccharides (dextrans, levans, other polysaccharides, glycogen), simple sugars, lipids, proteins, trace elements, calcium ions and phosphates.
Carbohydrates (polysaccharides, levans and dextrans) represent 20% of the dry weight of biofilm. They serve as an energy source for bacteria or act as a framework for the matrix and structure of the biofilm.
3.2. Bacteria : More than a dozen of them are now classified as pathogenic for the periodontium. Among these, there are mainly Gram-negative bacteria, in particular Pg, AgC, Tf, Td. Some of these bacteria have biochemical properties important for the pathogenesis of periodontal diseases. A stable ecological balance is gradually established in these complexes and among the bacteria involved, we differentiate between highly pathogenic complexes and low pathogenic complexes.
• Aggregatibacter actinomycetemcomitans serotype b which forms a complex on its own, not having been able to be brought closer to the other bacteria.
• the yellow complex: formed from Streptococcus spp.
• the green complex: Capnocytophaga spp., AgC serotype a, Ec .
• the purple complex: Veillonella parvula and Actinomyces odontolyticus .
• the orange complex: Cg, Cr, Cs, En, Pi, Pn, Pm, and the subspecies of Fn .
• the red complex: Pg, Tf and Td .
BIOFILM
Bacterial complexes of Socransky et al. (1998)
Some bacteria may secrete growth factors for others. In addition, intercomplex associations exist, with the orange complex being strongly related to the red complex, and the yellow and green complexes also being related.
4. TRANSFORMATION OF BIOFILM INTO SCALE
Tartar is defined as the mineralization of the biofilm producing crystals of different calcium phosphates. Dental tartar is mainly composed of mineral, organic and inorganic components. Initially, small crystals will appear at the periphery of the bacterial membrane. This phenomenon then extends to the entire interbacterial matrix and then to the bacteria themselves. The formation of crystals in the biofilm begins after 38 h and it takes only 12 days to obtain a well-calcified tartaric tissue.
Tartar is mainly formed by the precipitation of carbonate and phosphate ions from saliva. These mineral salts will be united by an organic matrix, epithelial cells, fat globules, leukocytes and bacteria. In addition, it would seem that alkaline saliva is an essential condition for the formation of tartar. There are two types of tartar:
¬ Supragingival tartar: Or salivary tartar located coronally or above the gingival margin. It is whitish in color, gelatinous in consistency, more or less easy to remove by manual scaling.
¬ Subgingival calculus: Or serum calculus located apically or under the gingival margin, in the sulcus or in the periodontal pocket. It is often much darker, harder and more difficult to remove by manual scaling than supragingival calculus.
BIOFILM
5. CLASSIFICATION OF BIOFILM
5.1. Supragingival biofilm: is clinically detectable only when it reaches a certain thickness, it then appears as a yellowish-white coating located first along the gingival margin. Its identification is carried out either by using a probe moved over the tooth surface or by staining. Supragingival plaque forms more quickly during sleep and is influenced by saliva. Patients with dry mouths have a high amount of supragingival plaque. Supragingival plaque forms quickly in patients following a diet based on soft foods, while fibrous foods that must be chewed delay plaque formation.
From 0 to 2 days: Multiplication of initially adherent microorganisms.
45% cocci G+: streptococcus
25% G+ rod: facultative or obligate anaerobes (actinomyces)
20% cocci G- . and 5% rods G- .
3 to 4 days : proliferation of fusiform and filamentous bacteria .
5 to 9 days: Appearance of spirillae and spirochetes (complex flora).
9 to 14 days Around the 14th day , the plaque becomes mature. It is composed of:
50% G+; 30% G-;
8% fusiform; 8% filaments;
2% vibrios; 2% spirochetes.
5.2. Subgingival biofilm :
It constitutes the apical continuity of the supragingival biofilm; it is the origin of periodontal diseases. An initial colonization by bacteria of the yellow, green and purple complexes at the same time as actinomyces modifies the environment in the biofilm, allowing bacteria of the orange complex first, then finally those of the red complex to develop and become the majority in subgingival biofilms.
| Attached to the tooth | Attached to the epithelium | Not attached |
| Does not extend to the junctional epithelium | Extends to the junctional epithelium | Extends to the junctional epithelium |
| Can penetrate into cementum | Can penetrate epithelium and connective tissue | |
| Associated with tartar formation and root caries | Associated with gingivitis and periodontitis | Associated with gingivitis |
6. PATHOGENIC POWER OF BIOFILM
6.1. Direct factors: Lytic enzymes
The enzymes produced by microorganisms are numerous and varied. Proteases and collagenases are the main lytic enzymes attacking the proteins constituting the periodontium.
- Exoenzymes: released by bacteria into the external environment, where they degrade the organic constituents that cannot diffuse through the plasma membrane. These are lipases, nucleases, proteases, polysaccharides and especially hyaluronidases.
- Ecto-enzymes: linked to the cytoplasmic membrane, which intervene in the penetration and metabolism of substrates within the cell, these are essentially permeases.
- Endo-enzymes: are intra cytoplasmic and come from an enzymatic excretion of the living bacteria into the external environment, but also produced following the destruction of the bacterial membrane.
| Enzymes | Action |
| Hyaluronidase | – Widening of the intercellular spaces of the epithelium. – Dissociation of the cells of the epithelium at the level of muccopolysaccharides with loss of desmosomes and other intercellular joints. – Decrease in the viscosity of the ground substance of the connective tissue. – Increase in the permeability of the connective tissue. |
| Collagenase | – Destruction of collagen fibers. – Alteration of the endothelial wall of capillaries. |
| Protease | – Protein degradation. – Decrease in acidic pH. – Destruction of collagen fibers. |
| B.Glucuronidase | – Role identical to that of hyaluronidase |
6.2. Indirect factors:
6.2.1. Toxins: Bacteria release toxins that play an important role in the progression of the inflammatory phenomenon and trigger the synthesis of lytic enzymes.
We distinguish:
- Endotoxins: Lipopolysaccharides are released following the destruction of Gram-negative bacteria.
They can cause:
- A pyrogenic action resulting in an increase in the temperature of the host.
- Transient leukopenia followed by hyperleukocytosis.
- Hypoglycemia.
- A decrease in resistance to microbial infection.
- A wide variety of circulatory disorders especially hemorrhages.
6.2.2. Antigens:
Antigens from bacteria are not completely inhibited by immune defense reactions, this reaction turns against the attacked organism and lyses it
the tissues it should have protected. We mainly have the wall antigens and those associated with the bacterial cytoplasmic membrane and the flagellar antigens.
7. FOCAL INFECTION
The bacterial aggression characteristic of periodontal pathologies results in tissue destruction modulated in particular by enzymes (metalloproteases) and proinflammatory cytokines, such as IL1 and (TNF) α, produced by the host cells. Hence the hypothesis recently put forward and confirmed by some studies that these compounds can play a role in the development of various general pathologies.
BIOFILM
CONCLUSION
Knowledge of the characteristics of biofilms should soon allow access to new therapies that are more respectful of the local environment, less harmful to the health of the individual and the community, and allow the establishment of a protective commensal bacterial plaque in balance with the host’s defenses.
BIOFILM
Wisdom teeth can cause infections if not removed.
Dental crowns restore the function and appearance of damaged teeth.
Swollen gums are often a sign of periodontal disease.
Orthodontic treatments can be performed at any age.
Composite fillings are discreet and durable.
Composite fillings are discreet and durable.
Interdental brushes effectively clean tight spaces.
Visiting the dentist every six months prevents dental problems.