Infectious leather - General and specific pathology in dentistry

Some microorganisms have a useful function in the body, while others are harmful. There are also microorganisms that are neither useful nor harmful, the commensals.

Infectious leather - General and specific pathology in dentistry
Some microorganisms have a useful function in the body, while others are harmful. There are also microorganisms that are neither useful nor harmful, the commensals.

Infectious leather


The microorganisms include:

  • Bacteria
  • Viruses
  • Fungi
  • Yeasts
  • Protozoa


Some microorganisms have a useful function in the body, while others are harmful. There are also microorganisms that are neither useful nor harmful, the commensals.


The useful and commensal microorganisms can become harmful if they end up in places where they do not belong (intestinal bacteria can cause an infection in the bladder). They can also become harmful through the use of antibiotics, for example. Other microorganisms with which they normally live in balance are killed by the antibiotic. The natural balance is disturbed and the commensal microorganisms can increase in number. The latter is, for example, the case with Candida albicans. As a result of antibiotic use, the oral bacteria are killed and the fungus starts to dominate. In addition to the useful and commensal microorganisms, there are the pathogenic (pathogenic) microorganisms. They can make people sick through direct damage to body cells or through certain toxins (toxins). When a pathogenic microorganism invades the body, we speak of contamination. If the microorganism can maintain and multiply in the body after being infected, then you have an infection.


There are many different microorganisms. Fortunately, the number of microorganisms that can be pathogenic to humans is small. The most important groups of microorganisms, bacteria and viruses are discussed below.



Bacteria are single-celled living organisms. They reproduce through cell division. Each bacterium has a cell wall, a core and cytoplasm. Pathogenic bacteria cause diseases if they can multiply in the body tissues. Our body (the host for the bacteria) is troubled by intruders. Pathogenic bacteria produce toxic (waste) substances that can end up in the tissue fluid or in the bloodstream. Those (degradation) products from bacteria can cause general and specific symptoms. Pyrogenic substances cause a fever. Toxins affect the tissues; for example, tetanus toxin affects the nervous system (see image below).


Micro-organisms can be seen with an electron microscope.


Bacteria are divided into groups according to their appearance. Examples of groups are:

  • Bacilli: Rod-shaped bacteria;
  • Kokken: Spherical bacteria;
  • Staphylococci: Lying together in clusters;
  • Streptococci: Forms dashes;
  • Spirils: Rod or helical bacteria.



A virus is a very small particle that is only visible with a so-called electron microscope. Unlike the bacteria, a virus has no cell wall and no cytoplasm. A virus consists of nuclear material (DNA or RNA) and is surrounded by a protein coat. A virus acts like a dead substance outside of a living organism. It cannot multiply there. A virus can therefore only be grown on a living breeding ground, such as a fertilized chicken egg.


A virus is pathogenic because the virus invades the cells of the host. There, the core material of the virus displaces the cell nucleus of the host. The host cell will then create virus material. As a result, the host cell no longer functions normally. The result is that symptoms of disease occur. Some diseases caused by a virus are: herpes simplex, aids, mumps, measles, chicken pox and hepatitis A, B and C.


Methods of contamination during dental treatment

In dentistry the treatments are limited to the oral cavity. There are countless microorganisms in and around the mouth that can cause diseases. There are patients who pose a risk of infection to dental personnel. The infection can occur through mucous membranes or air, but most of the time one should be aware of infection through wounds on the hands and puncture accidents.


Via cross-contamination, microorganisms of a patient can also pose a risk to other patients. Cross-contamination is the transfer of microorganisms from one person to another. This is not done directly, but via an infected object, contaminated surfaces and contaminated hands of the dentist or assistant.


Contamination can occur via various access routes, the so-called portes d'entrées.


General transfer methods of microorganisms

Our bodies can become contaminated by microorganisms in various ways.

  • Congenital: The infection takes place in the womb. The infection therefore passes through the mother to the unborn child.
  • Oralofenteral: The infection takes place through the mouth and the gastrointestinal tract. Contamination in this way can begin with the hands, food or drinking water. An example of this method of infection is hepatitis.
  • Via skin and mucous membranes: The infection takes place via (small) wounds in the skin and mucous membranes (wound infections, tetanus bacillus). Sometimes contamination occurs through direct contact with mucous membranes, such as with venereal diseases such as syphilis and gonorrhea and with Pfeiffer's disease ("kissing disease").
  • Aerogenic: The infection takes place via the respiratory tract. Coughing, sneezing and speaking can cause small water droplets to enter the air that are full of microorganisms. These droplets can be inhaled by others, and this is how contamination occurs. This method of infection occurs among other things in angina, diphtheria, tuberculosis (TB), scarlet fever, flu (influenza) and measles.
  • Hematogenic: The infection takes place via the blood. The microorganisms enter the bloodstream directly. This can happen with a blood transfusion with contaminated blood, an injection with contaminated needles or with a stab of an insect that carries the microorganism, such as the malaria mosquito.
  • Contamination by zoonoses: The disease is transmitted from an animal to humans. The deviation normally only occurs in animals, but can also make people sick. An example is rabies (rabies).


Spread of microorganisms throughout the body

The micro-organisms do not always remain at the site of infection after an infection. They can spread throughout the body. This can happen in different ways:

  • Via a phlegmone, an acute tissue infection where pus is formed. The process can expand very quickly.
  • Via the lymph lanes. The microorganisms use the 'fixed pipe network' of the body, the lymph system.
  • Via the blood vessel system. Here too, the micro-organisms use an existing transport system. When bacteria occur in the bloodstream, we speak of a bacteremia. When a tooth is extracted, a quantity of bacteria will circulate in the bloodstream temporarily. This short-term bacteremia does not cause any symptoms in a healthy patient. The leukocytes clear the invaders quickly. When so many bacteria enter the bloodstream that they can multiply and spread to all organs, we speak of a sepsis. A patient with sepsis is seriously ill and suffers from fever attacks. Sepsis can occur with any serious infection, but it usually occurs in patients with poor general resistance or a poor defense against bacteria.
  • Through the body cavities. The organs in the body lie against each other, separated by membranes. Although it is not really possible to speak of cavities, microorganisms can move along these membranes from one cavity to another and thus spread throughout the body.
  • Through the tubular organs in our body, for example the urinary tract and respiratory system. A microorganism can move within these tubular organs. An example is a rising urinary tract infection.


Virulence and resistance

Fortunately, a person does not get sick after every infection. Whether an infection actually leads to an infection depends on two factors:

  1. The virulence or attack power of microorganisms;
  2. The resistance to microorganisms.



By the virulence of microorganisms we mean the "attack power" of microorganisms. A microorganism is virulent if it is capable of causing a disease.


The number of microorganisms that invade the body naturally also has to do with virulence. The more intruders there are, the greater the chance of illness. There are other factors that also determine whether illness occurs after infection:

  • The place of infection;
  • The nature of the micro-organism: commensal or pathogenic.



We distinguish two types of resistance: general and specific. General resistance plays a major role in infections. Age, psychological factors, illnesses and nutritional status of the person determine the general body resistance. By specific resistance we mean the presence of antibodies against specific pathogens. This is very important for contamination with pathogenic microorganisms.


Reactions of the body to an infection

The body responds to infections with an inflammatory response. An ignition has five general characteristics (see image below):

  • Redness (Rubor);
  • Pain (Dolor);
  • Heat (Calor);
  • Swelling (Tumor);
  • Disturbed function (Functio laesa).


Inflammatory symptoms in the mouth.


With an infection, many white blood cells, leukocytes, will go to the site of the inflammation. These leukocytes can penetrate the blood vessel wall. At the inflammatory site, they attack the pathogens: leukocytes can, as it were, eat bacteria and destroy them within the cell. We call this process phagocytosis. With a bacterial infection the need for leukocytes is increased. This is because leukocytes can perish in the phagocytosis process, resulting in pus. Because more leukocytes are needed, the bone marrow will also produce more leukocytes. The result is that there are more leukocytes in the blood than normal. This phenomenon, more leukocytes than normal, is called leukocytosis.


With a small inflammation recovery can now occur: the leukocytes clear up the bacteria. The tissue fluid that is released during inflammation is cleaned up via the blood and lymphatic pathways. With more severe inflammation, however, usually death or necrosis will occur. Pus consists mainly of dead white blood cells, bacteria and sometimes necrotic tissue residues.


Gaining immunity

The body reacts locally to an infection with the five inflammatory symptoms rubor, dolor, calor, tumor and functio laesa. Moreover, leukocytes attack the intruders. The body will therefore try to provide healing itself.


Despite the body's attempts to control the microorganisms, inflammation can persist for a long time. This is possible without directly giving complaints. An inflammation that appears to be persistent is what we call chronic inflammation. A chronic inflammation can eventually cause symptoms, because the amount of inflammatory tissue increases or because the inflammatory process suddenly becomes acute.


In addition to the local reaction with the five inflammatory characteristics, other actions are being taken against the intruders. The body recognizes the invaded microorganism as a foreign substance. It can then produce specific antibodies. We call this an immunological response. Micro-organisms against which the body has made specific antibodies are called antigens.


This happens not only when microorganisms invade the body, but also during the transplantation of foreign organs or during a blood transfusion with the wrong blood type.


The formation of antibodies starts about ten days after the infection. Antibodies are also referred to as immunoglobulins or gamma globulins. These immunoglobulins are produced and transported through the lymphocytes. Immunoglobulins are specific, that is, they are only effective against the antigen (foreign body) against which they are produced.


The gamma globulins, which circulate in the blood, also disappear from the blood after a certain time. When the infection is effectively controlled, the lymphocytes (also a type of white blood cells) no longer produce antibodies. Because the body renews all blood components through degradation and production, the immunoglobulins will disappear from the blood. However, antibody renewal can occur quickly with renewed contact with the disease. This is because lymphocytes have the ability to 'withhold' an antigen against which an immunoglobulin has already been produced. So they quickly form new antibodies again. This ability of the lymphocytes to recognize pathogens is called immunity.


There are different ways to obtain immunity against pathogens.

1. Active immunity. The body must produce the antibodies itself. Active immunity can be divided into active natural immunity and active artificial immunity.

  • Active natural immunity occurs when someone becomes sick and the body's defense mechanism produces enough antibodies to combat the disease. After the disease, the antibodies disappear from the body again. Due to the 'memory' of the lymphocytes, renewed contact with the pathogen can quickly produce gamma globulin. The ability of the lymphocytes to produce gamma globulins again does not last the same time for all diseases: for one disease (eg for measles) lifelong, for the other (eg tetanus) only a few years.
  • Active artificial immunity means that here too the body must take care of the production of antibodies, but now the pathogen is artificially introduced into the body. The pathogen is administered in a strongly weakened form. We call this a vaccination. Because of this the body will not really get sick. Symptoms of the normal infectious disease, such as fever, do not occur. The formation of antibodies is not perceptible, the 'disease' is subclinical. The lymphocytes will make antibodies against the pathogen. If infection occurs at a later time with the same (but not weakened) pathogen, the 'memory' of the lymphocyte is able to quickly produce the correct immunoglobulins again. Some examples of vaccinations are DKTP (diphtheria, whooping cough, tetanus, polio (myelitis)), measles and rubella and hepatitis B vaccination for high-risk groups such as dentist and dental assistant.


2. Passive immunity. The body's immune system does not have to do anything to produce antibodies. The antibodies are brought into the body from outside. Passive immunity can also be subdivided into passive natural immunity and passive artificial immunity.

  • Passive natural immunity. The term "natural" means that this form of immunity is obtained without the intervention of a doctor. Passive natural immunity is therefore obtained from mother to child. During pregnancy, antibodies from the mother can cross the placenta and circulate in the bloodstream of the unborn child. For example, the child has protection from the mother's antibodies for a while after birth. Breast milk also contains antibodies and is important for the defense of the newborn child. The passive natural immunity provides protection for a few months, until the defense of the newborn child starts to work properly.
  • Passive artificial immunity. With this form of immunity, the body defenses of the sick or infected patient do not have to do anything. The patient only has to visit the doctor himself. This is because passive artificial immunity means that ready-to-use antibodies are administered to the patient via an injection. This is how immunity is obtained. An example of this form of immunity is the administration of the tetanus toxin ('tetanus prick') to wounds that (may) be contaminated with street dirt.


Anti-infectious agents

Sometimes it is too difficult for the body to remedy inflammation. If vaccination and administration of antibodies can no longer help, anti-infectious agents are used. These are, as the word suggests, medicines that work against the pathogens in infections. This includes antibiotics, antiviral agents and antifungal agents.


Relatively little use is made of anti-infective agents in dentistry. The dentist usually first treats the cause of an inflammation.


If an infection based on the teeth has already been greatly expanded, it may be decided to use anti-infective agents. This is done when it is expected that dental curative therapy alone will not sufficiently help. In certain patients, the so-called at-risk patients, it is (sometimes) necessary to take measures to prevent infection and infection. We will discuss this risk patients in another chapter.