Deposits forming on the teeth (Zsuzsanna Tóth DMD - Péter Vályi DMD)Vályi DMD)

For several centuries, the importance of good oral health has been emphasised in the literature. There is mediaeval evidence originating from more than 5,500 year old findings of the Babylonians on the removal of deposits formed on the teeth. The role of the deposits causing periodontal diseases and caries are proved by scientific studies. A wide variety of materials of different hardness, colour and adhesiveness originating from the oral milieu can be deposited on the natural and artificial hard surfaces in the mouth:

• acquired pellicle

• dento-gingival plaque

• calculus

• debris

• materia alba

The dental plaque is a strong adhesive layer on the surface of the teeth, restorations and dentures, which develops by the help of acquired pellicle, and it can be removed only by rubbing and not by mouth rinsing or water jet (Figure 2.26.). The main components of the dental plaque are bacterial strains colonising in the intercellular matrix, which are located in the biofilm (See Chapter 1.8). The supragingival plaque adheres above the gingival margin, and the subgingival plaque adheres under it.

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Dental plaque (from Prof. S. Kneist)

The materia alba is a greyish-white-yellow soft layer that is clearly visible also by the naked eye on the hard surfaces. It is less adherent in comparison with plaque, and it can be removed using a water jet. Its main mass contains bacteria, salivary proteins, detached epithelial cells, disintegrated leukocytes, and often food remnants as well.

Debris may be found on the teeth, between the teeth, and possibly also on the surface of soft tissues, which is food remnant in the mouth washable by water, but usually they are removed by the mechanical effect of muscle function and salivary flow.

THE ROLE OF DENTAL PLAQUE IN GINGIVITIS

There are bacterial colonies organized in a biofilm, as members of the natural bacterial flora are present in the healthy oral cavity without causing any disease. Small amounts of bacteria causing diseases can often be detected, but in healthy conditions the human organism‘s defence mechanisms are able to maintain a balanced state without any damage to the tissues. Due to strengthening of the bacterial effects or weakening of the body's defence mechanisms, the balance will be tilted and pathological changes, pathoses occur.

The biofilm forming microorganisms can be classified as symbiotic (apathogenic) and pathogenic microorganisms. Against the members of the symbiotic flora the organism will not trigger the tissue destruction causing, damaging defence mechanisms. The members of the pathogenic flora cause inflammation and promote the development of disease characterized by direct and indirect (inflammatory and immunological) damage of tissues. Certain risk factors influence the development and the process of the pathosis significantly (see chapter 2.15.1.).

The increase in the amount of dental plaque results in gingivitis. Gingivitis without any treatment will be followed by periodontal disease. In most of the cases the regular and efficient dental plaque removal prevents or heals the gingivitis. Frequently experienced gingivitis in pregnant women developing as a result of the hormonal changes is of great importance, but it is also related to the formation of dental plaque.

According to the non-specific plaque theory of Loesche W. (1976) and Theilade (1986) the quantity of accumulating dental plaque is the cause of the consecutive gingivitis. In larger amount of dental plaque more harmful bacterial decomposed products will be produced leading to inflammation of gingival tissues and growing worse to inflammation of periodontal tissues. In some cases however excessive mass of dental plaque of the neglected mouth does not result in serious medical consequences. Therefore scientific examinations have focused on the bacterial composition of the dental plaque, and it was found that certain well-defined pathogenic strains can be isolated, which have important role in the periodontal pathological processes, they cause disease and their removal causes the healing. That is the explanation also for the experience whereas the same large

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amount of plaque in the oral cavity of neglected patients can cause inflammation of different stages: mild or quite severe as well. According to the specific plaque theory (Loesche W. 1979) the disease of the periodontium can be explained not by the quantity of the dental plaque, but by the presence of some pathogens. Among the disease causing parodonto-pathogen bacteria there are only a few species, which can not be found or only in trace amounts (exogenous pathogens) in the healthy mouth. Bacteria also of the healthy organism cause very often opportunistic infections due to a change in circumstances (constitutional factors, quantitative and qualitative changes of the composition of dental plaque, risk factors etc.). This is the endogenous infection, which plays an important role in the development of inflammatory and destructive disease of the periodontal tissue (Wirthlin and Armitage, 2004).

There is not still correct answer received what a role is played by the mostly obligate anaerobic parodonto-pathogen bacteria strains in the aetioparodonto-pathogenesis of the disease, since they can not be the initiators of the disease because of their nature, they are likely responsible for the progression of the disease.

Formation and properties of dental plaque see in chapter, 1.8.

THE ROLE OF DENTAL PLAQUE IN CARIES

In the chapter on biofilm is already mentioned that the composition of various colonies found on the different surfaces, mainly due to the different environmental conditions is significantly varied. While the bacterial strains at the gingival margin and below them play a role in the inflammatory processes of gingival and deeper periodontal tissues, the bacteria of dental plaque accumulating on the smooth surfaces and in pits and fissures of the coronal part of the teeth are the etiological factors of dental caries. The metabolism of cariogen plaque‘s components produces acidic milieu which initiates demineralization. If they can not be neutralised and compensated by remineralizing processes, the dental hard tissue will be damaged.

The role of dental plaque bacteria in caries aetiology detailed can be found in the next chapter.

THE FORMATION OF DENTAL CALCULUS

In mature dental plaque accumulating on the surface of the teeth mineral salts can be precipitated and calcifying the plaque forming supra- and subgingival type of dental calculus.

The supragingival calculus

In the beginning the supragingival calculus is a yellowish-white porous deposit above the gingival margin (Figure 2.27.). The characteristic places are the predilection sites, where they appear very early and easily.

Typical localization of dental calculus formation is as follows: the opposite tooth surfaces of the salivary glands‘

outflow, for example lingual surface of the lower front teeth, and vestibular surface of upper molars. Typical experience is, that in neglected subjects chewing only on one side (unilateral chewing), also the occlusal surface of the teeth of opposite side will be covered by calculus. Without any oral hygiene deposits can be formed not only on the surface of the teeth, but on the surface of the restorations and dentures, prosthesis as well. The cleaning of the dental calculus can not be perfect, because of its rough outer layer. At first it is porous, but in the course of time it will be harder and harder, its removal needs considerable effort. Its colour can vary regarding the meals and beverages and depending on the by-product of bacterial metabolism originated on its surface developing plaque. Its colour can vary from yellowish-white to dark brown or black. Note that the role of dental calculus is determining in the process of development of periodontal diseases because it is an important plaque-retentive factor. Beside this it widens the gingival sulcus that is why the forming of subgingival biofilm will be possible. The bacterial toxins originated from the plaque of the calculus surface cause pathological tissue destruction. Every roughness of the tooth surface promotes the formation of dental plaque and calculus. In addition the accumulation will be facilitated by gaps, leakage, margins of fillings, restorations, prosthesis and orthodontic appliances beside the original dental conditions.

The subgingival calculus

Subgingival calculus can be formed only in the gingival sulcus of inflamed gingiva. There is no predilection place for its development, but there is no subgingival calculus below the healthy gingival margin (Figure 3). In case of thin gingival margin its dark bluish purple discolouration is visible also by naked eye. Its diagnosis is possible by periodontal probe, by removal of inflamed marginal gingival with air, and its interproximal localization is visible in the X-ray picture as well. Subgingival calculus develops due to the mineralization of subgingival dental plaque, its colour is black, and its surface is very rough. Its calcifying is originated from sulcus secretion and blood, that is why the supragingival calculus is from saliva and contrast with it

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subgingival calculus is originated from the gingival sulcus. It adheres very strong to the tooth, stronger than supragingival calculus. It can be explained by the roughness of the root surface and by the fact, that not only dental plaque but also the acquired pellicle will be mineralized.

Supra- (yellowish-white) and subgingival (brownish-gray) calculus

In the inter-bacterial matrix of dental plaque some components (proteins, fats) are centres of crystallisation, here starts the crystallisation from the supersaturated salt solution of the saliva. Dental calculus mostly contains inorganic salts (octa–calcium-phosphate, tri-calcium-phosphate, magnesium- carbonate, sodium carbonate) and later hydroxyl-apatite crystals. Supragingival calculus has a layered structure, the mineral content of the layers are different but the average value is lower than in case of subgingival calculus.

The supra- and subgingival calculus should be fully removed from the tooth surface. In case of subgingival calculus, frequently, it cannot be performed only with the accidental attenuation of the root cement.