Dental caries (Zsuzsanna Tóth DMD)

DEFINITION OF CARIES

Caries is damage to hard tissue in the presence of cariogenic microorganisms on erupted tooth surface covered by dental plaque. The chronic process is reversible in the initial stage but will be irreversible following cavitation. It extends from the coronal enamel surface towards pulp as a result of demineralising and remineralising processes depending on the frequency of the carious attacks. As a result of aging and recession of the gingival, caries can develop on the cementum and on the nude dentin as well. Over time the deep penetrating destruction results in pulp pathosis.

EPIDEMIOLOGY OF DENTAL CARIES

Epidemiology as part of medical sciences deals with pathological changes and epidemic diseases occurring on a large-scale. The existence, severity, frequency, development, spread and conditions of diseases are investigated regarding different parameters. These parameters can be e.g. the following: age, sex, occupation, qualification, behavioural and dietary habits, and geographical, social and economic conditions. After the evaluation of statistical data we may come to a conclusion about pathological factors, risk groups, therapeutical and preventive options, and about the effectiveness of therapy and prevention. Discovering the caries preventive effect of fluorides is also a result of epidemiological investigation.

Dental caries –besides inflammatory diseases affecting the periodontium – is the most frequent chronic disorder.

Its therapy is expensive for the society although only a few patients visit their dentist regularly. The right solution is prevention.

PATHOLOGY

Dental caries has been present since the start of human history. Its prevalence has increased to 90-100%

nowadays. In the 1970‘s and 1980‘s in some industrialised countries the increase stopped and then decreased, e.g. in the US, in western European countries, in New Zealand and in Australia. The decline can be attributed mostly to the presence of fluoride in the drinking water and later in the products of oral hygiene, first of all in toothpastes. Dental caries is a civilisational disease. In developing countries there used to be generally low values which rapidly increased with civilisation. There is a close correlation between disadvantageous dental caries conditions and dietary and oral hygiene habits.

Epidemiological survey

The participants in epidemiological studies are the population. Caries frequency (caries prevalence) shows the percentage of persons with carious teeth. The number of diseased teeth is expressed by caries intensity (caries experience). Horizontal or cross-sectional surveys provide information about the actual conditions, in a follow-up survey, or data of a longitudinal study are registered periodically (in case of caries: yearly) in the same way.

The changes in caries conditions can be determined. Caries increment reports new carious lesions, caries incidence indicates the number of persons with a new carious lesion.

DMF scores are individual quantitative data regarding caries; DMF index shows data of a group. It is a quotient: the sum of all DMF scores in the group should be divided by the number of subjects. DMF is an acronym, D means decay, M means missing and F means filled. DMF-T index (T means tooth) refers to carious teeth, DMF-S (S means surface) refers to tooth surfaces. The increasing depth of caries in the enamel is indicated by D1-D2 scores, dentinal lesions are indicated by D3-D4 scores. For primary teeth the nomination is the same but it is written with lower case letters: dmf-index. The indices df and def are widespread; in the second one e means deciduous tooth indicated for extraction. The df-t index refers to teeth and df-s index refers to tooth surfaces.

In comparative epidemiological caries surveys the data of the same age groups will be compared. Successful prevention and conservative therapy result in more remaining teeth in elderly patients although they have more periodontally involved teeth. The frequency of root caries on the exposed tooth neck is increasing due to gingival recession. RCI, root caries index expresses the quotient of carious root surfaces and exposed root surfaces. Recent epidemiological studies demonstrate an increasing number of root caries depending on age and remaining teeth. Root caries is more frequent in males and in lower teeth with the exception of the incisors.

DENTAL NOTATION

There are many nomenclatures in the literature for the definite identification of the 20 primary and 32 permanent teeth. In Hungary the Zsigmondy system is used the most frequently: the teeth are put in the Zsigmondy-cross.

The patient is sitting opposite the dentist, the mouth is divided into four quadrants and each permanent tooth is assigned a number from 1 to 8 starting at the midline.

Each primary tooth is numbered similarly but with Roman numbers from I to V starting at the midline.

Notation of teeth by Zsigmondy-system

PATHOLOGY

In scientific publications the two-digit notation of the World Dental Federation, FDI (Federation Dentaire Internationale) is adopted.

FDI notation of teeth (ISO system by WHO)

In the US the teeth are numbered simply following the quadrants clockwise from the upper right side numbering them continuously:

Universal numbering system "American method"

AETIOLOGY OF CARIES

Hundreds of theories explaining the development of caries have developed in the past centuries, many of which contain plausible mechanisms according to our present knowledge.

Modern theory of caries development

Dental caries is a disease of dental hard tissues with a multifactorial aetiology. Besides the four essential (primary) factors, secondary factors (e.g. biological, environmental, geographical, socio-economic, etc.) play an important role in the development of tooth decay.

The primary conditions for the formation of dental caries are (Figure 2.31.):

1. The surface of erupted tooth in the oral cavity 2. The microbial flora adhering on it

3. The substrate providing nutrients for microorganisms 4. The time factor

PATHOLOGY

The primary factors for the development of dental caries

Tooth surface as host indicates the importance of systemic factors. The outer cover of the crown, the enamel is the hardest tissue of our body, but it is still susceptible to environmental harmful effects. The enamel is of ectodermal origin, has an acellular structure, no circulation, and it is unable to defend itself or to reverse already existing tissue damage. In the oral cavity after eruption, the tooth surface as host is covered by a biofilm (dental plaque). The dental plaque is a strongly adhesive bacterial aggregate on the surface of oral structures which can only be removed by intensive mechanical cleaning. In the dental plaque there are microorganisms and nutrients as well.

Biochemical reactions taking place between the enamel and the dental plaque are in a dynamic equilibrium. This balance is disturbed during food intake. After carbohydrate intake (carious attack) microorganisms produce organic acids (such as lactic acid) by the degradation of carbohydrates. This decreases the pH of dental plaque.

The mineral components of hard tissue (e.g. calcium, phosphate) are dissolved, this process is called demineralisation. With the disappearance of carious attacks under the influence of saliva, pH is increased and remineralisation processes predominate. By the diffusion of calcium and phosphate (mostly in the presence of fluoride) the demineralised surface is remineralised.

Demineralisation and remineralisation processes occur many times a day. The frequency of carious attacks leads to a dominance of demineralisation, to macroscopic lesions and irreparable cavitation (Figure 2.32.).

PATHOLOGY

Carious cavity on the upper left wisdom tooth buccal surface

The significance of the time period is closely related to frequency. The more often the surface is exposed to carious attacks, (demineralisation) (e.g. due to frequent snacking), the less time is available for remineralisation (Figure 2.33.).

Changes of dental plaque pH according to the frequency of food intake (Bánóczy , 1990).

In addition to primary aetiological factors, many biological, behavioural, environmental, geographical, socio-economic factors play a role in influencing the likelihood of caries development

Microbiological background of caries

The complex and dynamic relationship between bacterial plaque, host and diseases in the oral cavity is the result of a working ecological system. The oral microflora of a toothless baby is poor, it will be rich in the presence of

PATHOLOGY

teeth, but under elderly edentulous circumstances the situation is similar to childhood. Only a limited number of bacteria of the 400-500 types existing in the oral cavity have an important role in caries development (cariogenesis). Dental plaque accumulates on the tooth surface in a determined sequence. Most of the microorganisms leave the mouth by swallowing and only a few of them are able to stay and adhere to soft and hard tissues. At different places of their retention there are different complex colonisations. That is why it is hard to prove the direct casual relation between the caries process and one single pathogen, but the role of Streptococcus mutans and Lactobacilli is definitive in caries development and progress.

The shape of the tooth is important in dental plaque formation and in caries development. In retention places of grooves, pits and fissures dental plaque adheres very easily, but plaque removal is complicated, and these retention places are harder to assess for the rinsing and protecting effect of saliva. Saliva is a very important endogenous factor against caries development. In case of dental congestion, there are hardly any places that can be cleaned effectively, and these are optimal for plaque retention. The role of dental plaque is dominant in caries development and do not forget its important role in the aetiology of periodontal diseases.

Formation of the dental plaque (see under II. Pathology, in chapter 12. Deposits forming on the teeth)

The dental plaque adheres to undisturbed surfaces, where the cleaning effect cannot operate due to the movement of soft tissues while chewing. In caries aetiology the supragingival plaque has special importance.

Dental plaque in the development of caries

The dental plaque is an ecological community: if it produces mostly organic acids, under it caries will develop.

Initially the composition of the dental plaque is rather aerobic, and has low pathogenicity. The maturation process results in a mostly anaerobic combination. Carbohydrates metabolised to organic acids cause significant and long lasting decrease in pH. At pH between 5.0 and 5.5 demineralisation starts in the enamel: under the clinically intact enamel surface the subsurface mineral content decreases, becomes porous. After drying its appearance is chalk-white and opaque (incipient caries). This stage is still reversible, and in the presence of fluoride the enamel can be remineralised, which results in a hard and acid-resistant enamel surface, more resistant than the original was. The dental plaque is different in caries free and caries active individuals. In caries-resistant persons fasting pH is higher. If the plaque-pH remains under the critical pH of 5.5 for a period of 20-50 minutes after a single sucrose intake, it is called caries active. The acid production of the caries active plaque is twofold than the acid production of caries inactive one. Note that the consumption of sweets between main meals results in a constant acidic attack on the tooth surface.

The role of saliva in the development of caries

Saliva is particularly important in cariogenesis. The water and mucin content of saliva moistens the mucous membranes and helps taste and swallowing. An adequate amount of saliva (appropriate level of flow rate) cleans the oral cavity from a significant part of food remains, microorganisms and dissolved metabolites by its mechanical washing and diluting effect. This role inhibits the development of caries. The lubricant components of saliva facilitate speaking. Mucin and mucoid content increases viscosity and thereby facilitates the formation of dental plaque and consequently, the formation of caries as well. Enzymes of the saliva already start to digest nutrients in the oral cavity; carbohydrate breakdown results in an acidic pH in the mouth promoting caries development. In contrast to this, however the caries inhibitory properties of saliva predominate. The high number of bicarbonates has a buffering effect; its efficiency is enhanced by phosphate and to a certain extent by the protein buffer system as well. The antibacterial activity of saliva is provided partly by immune proteins and enzymes. Growth factors in saliva promote wound healing; inorganic ions (calcium, phosphate, fluoride) promote the remineralisation of enamel. Decreased salivary secretion (xerostomia) reduces the amount of protective proteins (protective function) and reduces acid and carbohydrate clearance. A decreased salivary flow rate is a physiological phenomenon of aging, menopause, symptoms of some diseases, for example psychic disorders, autoimmune diseases of the salivary glands (e.g. Sjögren's syndrome) or diabetes mellitus. It can be associated with anaemia, dehydration, vitamin deficiency or pregnancy as well, and can also occur as a result of drugs. The reduced production of saliva leads to caries increment.

Nutrition and caries

Food intake is of crucial importance in dental caries and in periodontal diseases because it provides the essential nutrients for the microorganisms in the dental plaque. The composition and consistency of food, the way, the quantity, the frequency of food intake and the duration of residence in the mouth are all important factors. Its effect can work in two ways:

PATHOLOGY

• praeresorptive effectprevails in the oral cavity before the absorption in contact with teeth and other oral surfaces during chewing.

• postresorptive effectis a systemic effect after absorption, as in the developmental period of teeth before eruption (praeeruptive).

Other factors affecting caries development

In addition to the primary factors in the aetiology of dental caries there are also non-negligible secondary factors playing a role in the process, for example macroscopic and microscopic properties of the teeth, physique (genetic background), age, sex, hormonal and immunological factors, and some geographical, social and economic factors.

THE LOCATION OF CARIES

Caries develops if in the presence of bacteria, the balance of demineralisation and remineralisation processes is upset, leading to increased demineralisation. The anatomical location of caries is on the crown and on the root.

Morphological and histological differentiation is based on enamel, dentin and cement tissue. Predilection sites are areas susceptible to caries development. The predilection sites are the non- self-cleaning surfaces, so-called habitually unclean areas. As a result of self-cleaning, the dental plaque disappears from tooth surfaces which are in contact with the lips, tongue, and bucca due to speaking and chewing or due to the abrasive effect of food. To clean the non- self-cleaning or habitually unclean areas is often very difficult. The caries susceptible predilection sites are as follows (Figure 2.34.):

1. pits, grooves, fissures,

2. smooth surface interproximally below the contact point, 3. smooth surface at the gingival border,

4. root surface.

Caries predilection sites (Wannemacher 1963)

PATHOLOGY

Crown caries

Crown caries means circumscribed carious lesions developing on the tooth crown in pits, fissures or on the smooth surface (Fig. 2.35.).

PATHOLOGY

Fissure caries

To clean deep and narrow fissures is often impossible; in this case fissure sealing in due time is possible to prevent caries formation (Fig. 2.36., see under IV. Prevention, in chapter 5. Fissure sealants). Pits and fissures are to be found on the occlusal surface of premolar and molar teeth and on the palatal surfaces of the upper incisors (foramen caecum).

PATHOLOGY

Fissure sealing

Areas between the gingival margin and equator of the crown are not self-cleaning smooth surfaces, although it is easy to clean them because of good access. Caries in these areas draws the dentist‘s attention to the lack of oral hygiene or disorder of saliva production (Figure 2.37.).

PATHOLOGY

Caries at the gingival margin

The approximal smooth surface of the teeth below the contact point belongs to habitually unclean areas. The cleaning of this area requires some manual skill and the use of tools for oral hygiene besides the tooth-brush (e.g. dental floss, interdental brushes) (Fig. 2.38.).

Approximal caries Root caries

Nowadays more and more elderly people have their own teeth, but often the root surface is exposed. This area is not self-cleaning, plaque formation is promoted also by the decreased saliva flow rate. Due to the deterioration of manual skills, cleaning is problematic. At the enamel cement junction a soft, irregular, often discoloured lesion develops and extends relatively quickly.

PATHOLOGY

THE EXPANSION OF CARIES

Dental caries is a pathological process extending from the enamel (root cement) surface through the dentine toward the pulp into the depths. Because of the prismatic structure and the different formation of enamel prisms, the cross-section of fissure caries and smooth surface caries are different in the enamel. There is no difference in the dentine, which has a tubular structure, and in both cases the cross-section is similar (Fig. 2.39.).

Smooth surface caries and cross-section of groove

Primary dental caries (caries primaria) occurs on an intact tooth surface which is not self-cleaning. Secondary caries (caries secundaria) develops along the margin of crowns, fillings or inlays placed in the teeth. In the stage of caries incipient the enamel surface is carious without any clinically or histologically macroscopic cavity formation. There is a chalky white spot on the tooth surface, and it becomes porous (Fig. 2.37.). From the occlusal surface at the bottom of the fissure, developing incipient caries appears to be a dark or an opaque area.

The therapy of incipient caries is remineralisation. Superficial caries is a cavitated lesion progressing to the dentine. Caries media extends to the dentine, the deepest part of the process is far away from the pulp chamber.

The differences in colour, transparency and the changes in the surface and the contour are visible to the naked eye as well, the break in continuity is tactile by a dental probe. Caries profunda is an extensive carious process, at this stage there is only a thin intact dentin layer between the pulp chamber and the carious process. In the case of caries penetrans the carious process has extended into the pulp, which communicates with the oral cavity.

The contamination of the pulp leads to inflammation.

THE TIME COURSE OF CARIES

Dental caries is a chronic disease. Between the incipient stage and the clinically diagnosed cavitated the development takes about 18 ± 6 months. The process extends faster in the pits and fissures than in the smooth surface. If poor oral hygiene is connected with snacking, the frequency of daily carbohydrate intake is high, incipient enamel caries can develop in three weeks. X-ray irradiation leads to xerostomia, which can cause dental caries in three months. In healthy subjects the development of caries is slower. Depending on the time, an acute and a chronic type of caries can be distinguished despite the chronic character of the process. The disintegration of the enamel and cavity formation in children develops rapidly; it is caries rapida (florid, or rampant caries). The lesion is white coloured (caries alba), it is filled with crumbly pasty mass (caries humida). At older age, when the dentinal tubules are narrower due to calcification, the process advances more slowly (caries tarda). The lesion itself is drier and harder (caries sicca), and the area has a dark brown or black discolouration (caries nigra). Stationaer or chronic caries means a carious process, which does not show further progress after the cessation of the cariogen attacks (insistens caries, arrested caries). During remineralisation, the enamel surface gets dark brown and black due to exogenous discolouration.

PATHOLOGY

The acid solubility of the enamel will be reduced, its surface will be more acid resistant compared to the original condition if remineralisation occurs in the presence of fluoride. This situation can be seen, for example in approximal caries after the extraction of the adjacent tooth. Latent or hidden caries is difficult to diagnose. In this case the carious lesion involves the dentine as well, and the process extends into the depth although the

The acid solubility of the enamel will be reduced, its surface will be more acid resistant compared to the original condition if remineralisation occurs in the presence of fluoride. This situation can be seen, for example in approximal caries after the extraction of the adjacent tooth. Latent or hidden caries is difficult to diagnose. In this case the carious lesion involves the dentine as well, and the process extends into the depth although the

In document HANDBOOK OF DENTAL HYGIENIST (Pldal 110-122)