tooth health

Caries: causes and risk factors


Caries is a multifactorial pathology in which there are many predisposing conditions, some of which are still unknown. In fact, hundreds of hypotheses have been formulated to find an explanation on pathogenesis and origin of caries. What is certain is that caries is due both to exogenous causes and to endogenous factors, in the presence of a particular genetic predisposition.

Constitutional factors weigh heavily on the triggering of caries: some individuals, in fact, seem exceptionally resistant to cariogenic processes, unlike others that are extremely subject to caries. However, the familiarity with the disease could derive from the transmission of unhealthy habits, such as excessive consumption of sugar or poor oral hygiene.


Some constitutionally robust people, despite having acquired good manual dexterity in proper home dental cleaning (with toothbrush, toothpaste and dental floss), prove to be prone to dental infections in general and caries in particular.

Other individuals, on the other hand, despite having bad and disorderly dental hygiene and a slender build, exhibit an extraordinary constitutional resistance to tooth decay.

Endogenous causes

The endogenous causes intervene in the earliest phases of the cariogenic process, thus favoring its onset. The following are among the endogenous causes predisposing to caries:

  • Quantity and quality of saliva : with its action, the saliva is able to buffer the acidity of the mouth. Thanks to some substances dissolved in it it also has an antimicrobial, immune and protective function against cariogenic agents. It follows that any condition that leads to reduced salivary secretion, makes it more viscous, or lowers its pH (as happens, for example, during pregnancy) predisposes the teeth to bacterial attack. For example, pathologies like Diabetes Mellitus, diabetes insipidus, Sjögren's syndrome and sarcoidosis favor caries because they reduce the amount of saliva. Even the administration of some drugs (eg antihistamines and antidepressants) can decrease the amount of salivary fluid, thus favoring tooth decay.
  • Characteristics of the teeth : the structural characteristics of the teeth greatly affect the possibility of caries formation. An accentuated interdental groove will favor, for example, a greater stagnation of food residues which, as we know, are fertile ground for bacterial development.

There are also individual differences in the degree of dental mineralization; obviously, the more the tooth is rich in minerals and the more it will be protected from external aggressions.

Exogenous causes (external or local)

The exogenous causes of caries act directly on the outermost surface of the tooth, at the precise point where the infectious process begins. The list of exogenous causes that can favor a cariogenic process includes:

  • Dental plaque, the main causative agent of caries. The dental plaque, a patina adhering to the surface of the teeth on which the bacteria develop, originates from the precipitation of salivary proteins and mucoids: in such circumstances, the bacteria adhere and proliferate.

    Did you know that ...

    The dental plaque is not necessarily a reason for infections: within certain limits, a thin layer of plaque adhered to the teeth protects the enamel from the direct action of acidic foods. Clearly, the more the microbial flora increases, the greater the risk of caries onset.

    Although there are hundreds of microorganisms, in the fully formed bacterial plaque, Streptococcus mutans (in particular the cricetus, rattus, ferus, sobrinus), Lactobacillus acidophilus, and actinomycetes predominate. Among these the lactobacillus has the highest cariogenic power. It feeds on the glucose present in food residues, forming lactate as a waste product. Thanks to its acidity, this substance is able to gradually dissolve the dental enamel, affecting the dentine. The streptococcus mutans intervenes instead in the formation of the bacterial plaque on which the other pathogenic microorganisms adhere.

    It is important to point out that the bacteria just mentioned, involved in caries, are not specific: although they cause the onset of the infection, they do not act through their toxins, but rather by releasing the products of their metabolism. The bacteria are not the only ones responsible for caries. Indeed, there are other factors that can facilitate its appearance. Let's see them in detail.

Feeding : it is scientifically proven that excessive consumption of sugary foods (sweets, sweets, sweetened drinks and the like) alters the natural bacterial balance of the oral cavity, predisposing the subject to dental caries. Sucrose is in fact formed by the union of a fructose molecule and a glucose molecule, which as we have seen represents the main nourishment for the lactobacilli.

  • Did you know that ...

    Some statistical studies show that those who consume sugars out of meals over 4 times a day are highly prone to tooth decay. The most sticky sweeteners (for example caramel) are the most cariogenic because they tend to stay longer in contact with bacterial plaque.

    Generally speaking, it is possible to state that an individual tends to develop less caries if he is adequately fed, fully respecting the methods of cleaning the oral cavity. Furthermore, to prevent cavities, it is advisable to regularly take an adequate amount of mineral salts (calcium, magnesium, fluorine and phosphorus) and vitamins, which are essential for ensuring the health of dental tissues.

    Tobacco : the smoking habit triggers a series of literally disastrous chain events for tooth health. In addition to making teeth yellow, smoking promotes dental infections, including tooth decay. Suffice it to say that some types of tobacco contain a high sugar content, consequently increasing susceptibility to caries. But that's not all: smoking is a significant risk factor for periodontal disease (pyorrhea), which in turn is responsible for gum recession. The retracted gums favor the progressive exposure of the dental necks, which therefore become increasingly visible in the mouth. In such circumstances, the bacteria that are the protagonists of the cariogenic process are facilitated in their unstoppable destructive process: without necessarily piercing the enamel, the pathogenic micro-organisms find the ideal conditions to create a deep damage to the dental pulp (in a relatively short time) starting precisely from the collar dental.

Risk factors

In favorable circumstances, the bacteria are able to trigger a cariogenic process very easily. The endogenous and exogenous causes just described can in fact be supported by additional risk factors:

  • Age : tooth decay is a typical (but not exclusive) childhood disease, a period in which children are particularly attracted to sweets, sugars and delicacies of all kinds. To be considered also an important constitutional factor: at an early age, the teeth are more exposed to the risk of caries because the degree of dental mineralization is much lower than that of an adult.

    In general, the age most favorable to the onset of caries is between 4 and 8 years and between 13 and 18.

  • Gender : despite the differences in the frequency of cariogenic processes between the two sexes are almost negligible, the statistics reveal that the female is slightly more predisposed to the formation of dental caries.
  • Race : it seems that also the breed influences the pathogenesis of caries. In the US, for example, black individuals living in the same conditions as the white population seem to be less susceptible to karyogenic processes than white complexion groups.
  • Geographical location and climate : it seems strange, but in places with a prevalence of clayey soils, patients affected by caries are much more numerous than those that inhabit calcareous soils. Moreover, from the scientific evidence it is clear that the increase in the external temperature hinders, in some way, the development of caries; on the other hand, an excess of environmental humidity seems to considerably increase the number of fillings required to treat superficial or medium caries.
  • Pregnancy : the incidence of pregnancy in the pathogenesis of caries remains an open question. If on the one hand the statistics reveal a poor correlation, on the other hand the clinical evidence shows a significant increase of new carious lesions during the sweet wait.
  • Some diseases : the presence of some serious pathologies can favor the formation of cariogenic phenomena. These include: typhoid fever, anemia, uncontrollable vomiting, chronic diarrhea, eating disorders with self-induced vomiting, and drug addiction.
  • Last but not least, we find poor dental hygiene : an insufficient removal of food residues and plaque is directly linked to the appearance of caries. Bacteria - attracted by rotting food fragments and not removed with dental floss, toothbrush and toothpaste - can easily give rise to tooth decay: by first attacking the enamel, the micro-organisms target the dentin until it reaches the dental pulp.

From what has been said, it is easy to understand how it is indispensable to dedicate daily, several times a day, a few minutes of one's time to dental hygiene: healthy and strong teeth constitute an (almost) unassailable protective shield against the onset of caries.

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