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Caries risk assessment

"Risk" is defined as "the probability that some harmful event will occur". To predict if new carious lesions (a "harmful event") will develop, or if early lesions will continue to grow, is to assess the caries risk. The importance of properly predicting the occurrence of lesions is obvious as targeted preventive actions can be directed to those persons having a high risk for caries, and scarce resources can be properly utilized.

When should caries risk assessment be performed? In a population where a majority of people are caries-active, there is little use of risk assessment, as a population strategy is more effective (= general preventive measures given to everyone). Likewise, in a population where practically no persons develop caries, risk assessment would be of little use. Assessment is highly indicated in populations where a large portion is caries-free, but some individuals are still high caries-active - and also where resources are available to take care of these targeted persons.

How to select risk groups or risk individuals? Several attempts have been made, but so far the "perfect" method is missing, which is not surprising considering the multifactorial etiology of dental caries. On the other hand, there are several factors and characteristics that often accompany the development of an increased number of carious lesions, the reason why evaluation of such parameters often are helpful in caries risk assessment. Below are listed some such factors. In considering them, it is important to differentiate between factors that are directly involved in the biochemical events resulting in the carious lesions, and factors or circumstances that are indirectly related to such events, somtimes referred to as "risk indicators". The presentation starts with a number of the risk indicators, followed by factors involved in the biochemical process.

A. Risk indicators

    Socio-economic factors or circumstances which may indicate increased caries risk, examples:

  •  
    •  
      • Socially deprived, no work, bad economy
      • Low knowledge, low education of parents
      • No regular dental check-up
    •  
      • Geneneral diseases
      • Various handicaps
    •  
      • Living in high DMF country
      • Living in high DMF area
      • Member of high DMF family
      • High past caries experience
      • Intra-oral distribution of earlier lesions/fillings
    •  
      • Early signs of the disease (for example white spot lesions)
      • Newly erupted teeth
      • Exposed root surfaces
      • Crowded teeth
      • Deep fissures or other "natural" retentive sites
      • Retentive sites caused by dental treatment
  • But why are these factors related to caries? For example: The conditions can result in more cariogenic food, in less good oral hygiene, saliva problems, reduced fluoride support. It should be observed that 'bad economy' under certain circumstances may promote caries, for example if carbohydrate products in the area are cheaper than proteins. In another society, 'bad economy' may work in the opposite direction, as there will be no money to buy sweets.

    Factors related to the general health which may indicate increased caries risk, examples:

    But why are these factors related to caries? For example: Several diseases, or their treatments, affect saliva secretion. Also, the conditions can result in more cariogenic food and in less good oral hygiene. Handicaps can in various ways affect oral hygiene.

    Epidemiological factors or circumstances which may indicate increased caries risk, examples:

    But why are these factors related to caries? For example: Country/area/family can be characterized by frequent intakes of cariogenic food, high mutans streptococcal load, less good oral hygiene, low fluoride in drinking waters. High past caries experience indicates that the individual is susceptible and/or have been under cariogenic challenge - the same factors that caused the past disease may still be in operation. The distribution of earlier lesions/fillings reflect to some extent the cariogenic pressure that has been in operation. Fillings/cavities in front teeth in the lower jaw, for example, indicates a serious situation, as these teeth normally are the last ones to be affected by caries.

    Clinical findings which may indicate increased caries risk, examples

    But why are these factors related to caries? For example: Early signs of the disease can reflect an ongoing caries process and is therefore not a real risk indicator, as the "risk" stage has already passed. However, it is a risk factor in that sense that the caries process may continue also in the future. Newly erupted teeth and exposed root surfaces are less resistant. Crowded teeth and various retentive sites, including orthodontic appliances, indicate risk for increased plaque accumulation and reduced saliva flow over the tooth surfaces concerned.

For each of the circumstances or findings mentioned above, the reason why they may indicate increased caries risk is that they in one way or another reflect, or affect, the biochemical events on the tooth surface where a carious lesion may develop.

B. Biochemical factors

    Factors to which the toothsurface is directly exposed, and which contributes to the development of the lesion.

    These factors may, depending on the "dose" and "duration", indicate higher or lower risk for caries.

FACTOR

HIGH RISK

LOW RISK

Amount of plaque Large amount of plaque on the teeth, meaning many bacteria that can produce acids (low pH, demineralization) Few bacteria = "good" oral hygiene
Type of bacteria Large proportion of "cariogenic" types of bacteria, resulting in lower pH and sticky plaque and also prolonged acid production Low proportion of "cariogenic" types
Type of diet High in carbohydrates, in particular sucrose; "sticky" diet leading to low pH longer time Low sugar content; non- "sticky" type of diet
Frequency of carbohydrates High sugar frequency resulting in longer time per day with low pH Low sugar frequency
Saliva secretion Reduced saliva flow leading to prolonged sugar clearance time and to a reduced amount of other saliva protective systems Optimal, helps to wash out sugars and acids
Saliva buffer capacity Low buffer capacity resulting in prolonged time with low pH Optimal, time with low pH shorter
Fluorides Absent: reduced remineralization Available: increased remineralization

    Each of the factors has to be considered in terms of "dose" and "duration". For example, a large amount of plaque ("high dose") only indicates high risk if present for a longer period of time ("long duration").


Discussion

Terminology

The use of and distinction between the terms 'Risk indicator' and 'Risk factor' differs in medicine, toxicology and dentistry, as well as between how different authors use the terms. The "classic problem over the distinction between association and causation (or disease etiology) .... is still a controversial and somewhat philosophical issue" (Colton T. Statistics in Medicine). Therefore this issue will not be discussed in detail here. We believe that if the chain of events leading to disease is understood properly, the problems in terminology should be possible to overcome.

Evaluation of factors

Several studies have tried to evaluate how accurate the parameters (described above) are to predict development of caries. Several such studies are found in the references (see below). Often, methods such as simple correlation, sensitivity/specificity or positive/negative predictive values have been used, methods which are suitable to test for example the accuracy of analytical methods, but not factors in relation to a multifactorial disease. Consequently, practically all those attempts have given low or moderate values. Nevertheless, using one or several factors in combination often illustrates the caries risk in a for the clinician helpful way.

Sometimes 'past caries experience' is said to be an efficient parameter to predict caries risk. It should though be understood that as soon as proper preventive measures have been introduced, and thus eliminated the caries risk, 'past caries experience' is not a valid factor any more (if it was, a person with several fillings would never be able to come out of the classification 'high caries risk'). Similar discussion is relevant for early lesions (if it not is possible to differentiate correctly between active and passive incipient lesions).

We believe that the 'biochemical factors' mentioned above are the one that in the best way can predict for new caries. The indicators are good to explain the reasons way the biochemical factors are favourable or not. For ther clinician, combining different parameters with the 'clinical feeling' may give proper results.

The picture shows a case with large amounts of dental plaque, which has covered the teeth for a long period of time (=high dose, long duration). According to the Table above, these findings indicate "high risk".

However, no carious lesions had developed over several years - the reason being that other direct factors were favourable (low mutans streptococcal load, low and infrequent sugar consumption, some natural fluoride in water, normal saliva).

Nevertheless, the plaque situation is a risk factor, which under other circumstances could have resulted in cavities. The case illustrates the complex interrelationship of etiological factors and the need for an explanatory model which can handle such information in assessment of caries risk. In the Cariogram concept, we have tried to develop such a model.

 





Test for risk assessment

Download Cariogram

Caries risk assessment in Pub Med

Senast uppdaterad av Magnus Jando