The 2 players: biofilm and the host

Your mouth, a genuine ecosystem!

Don't panic! Bacteria (more than 200 species) are always present in your mouth, even when you are in good health. These bacteria constitute a flora that maintains a stable relationship with you and that has no impact on your health. Beware however, any disruption to this equilibrium may have an impact leading to periodontal disease.

Biofilm, a 5-step formation process.

The bacteria present in your mouth attempt to colonise all favourable niches, in particular the hard surfaces
(teeth, implants, prostheses, etc.).
The majority of these bacteria are able to survive and multiply by forming a biofilm on these surfaces.

This biofilm can be divided into:
. supragingival biofilm that forms on the dental crown
. subgingival biofilm, located in the gingivodental crevice

Biofilm forms in 5 successive steps:
. Step 1: formation of a non-bacterial salivary pellicle
. Step 2: attachment of bacteria, either alone or in colonies, on the salivary pellicle or enamel
. Step 3: colonisation of the tooth and binding of bacteria to each other
. Step 4: bacterial multiplication resulting in the formation of micro-colonies
. Step 5: complex formation by microcolonies = biofilm
Biofilm forms in the space of several hours to several days.
Warning: Biofilm represents a protective barrier for its component bacteria, that can then become increasingly aggressive.

Your body, a shield with a varied defence system.

Your body possesses several mechanisms for preventing bacterial infection.
Indeed, you possess both physical and chemical barriers (skin, mucous membranes, saliva, etc?) that, when insufficient, are backed up by your immune system. This latter constitutes the most important of defence mechanisms.
 The immune system can be broken down into:
. "innate" immunity, that is naturally present.
. "acquired" immunity, that develops in response to diseases encountered.
Your defences may be weakened by certain specific factors such as tobacco consumption, diabetes, inappropriate brushing of teeth, etc.

Biofilm-host, a balanced relationship.

A balance is reached between biofilm accumulation and reduction. Without certain host-specific biofilm reduction actions, this latter would accumulate indefinitely.
Biofilm reduction actions are:
. self-cleaning mediated by the cheeks and tongue,
. diet,
. tooth brushing

Disrupted biofilm-host equilibrium:

periodontal disease
An imbalance between the biofilm and your defence mechanisms may occur as a result of:
. An increase in one bacterial species within your oral ecosystem, rendering it more aggressive.
. A drop in the efficiency of your physical and chemical barriers and of your immune system, due to "risk factors" that weaken your defences.

The host, whose defences have been weakened, thus experiences greater difficulty in combating the biofilm, thus presenting a fragile profile used advantageously by one or more bacterial species.
This imbalance created by one and/or the other, will determine the appearance and progression of a periodontal disease.

How does tartar form?

The tartar on your teeth is the result of calcification (calcium deposit) of the existing biofilm. It is a white or brown substance that forms on your teeth or on any other hard surface in your mouth.
As for biofilm, we can distinguish supragingival tartar (on the crown) from subgingival tartar (in the gingivodental crevice).
The amount of tartar formed is governed by individual factors such as the composition of saliva, dental hygiene, etc. It therefore varies from one individual to another.
Once formed, the tartar can only increase, particularly in difficult to clean areas. You cannot eliminate it yourself, it must be removed by your dental surgeon.
The tartar protects and promotes the development of biofilm and hence the appearance of periodontal disease

References :
Bercy P. Le parodonte sain et ses modifications histopathologiques. In Bercy P, Tenenbaum H. Parodontologie, du diagnostic à la pratique. 1st Ed. Bruxelles, De Boeck Université; 1996. p.13-23.
Mouton C. Bactériologie et pathogénie des maladies parodontales. In Bercy P, Tenenbaum H. Parodontologie, du diagnostic à la pratique. 1st Ed. Bruxelles, De Boeck Université; 1996. p.37-47.
Wolf HF, et al. Parodontologie. 3rd Ed. Paris, Masson; 2005. p.23-66.