Are there still bacteria in saliva after it dries?

Saliva is a liquid in the human mouth. It contains human bacteria, various viruses and antibiotics. It also contains some trace elements of the human body. It also contains some proteins in the human body, as well as parasites or germs in the teeth or mouth. When saliva is spit out, these substances will survive in the saliva. Generally, there will be certain bacteria after the saliva dries, but the amount of bacteria is very small and will not cause harm to the human body.

Saliva is nearly neutral, with a pH of 6.6 to 7.1. An adult secretes about 1 to 1.5 L of saliva per day, of which about 99.4% is water, and the rest is salivary amylase, lysozyme, and a small amount of inorganic substances (such as inorganic salts containing sodium, potassium, and calcium). So after drying, there will be a very small amount of inorganic matter left, which is invisible to the naked eye, and saliva bacteria

The oral cavity is one of the main pathways for bacteria, viruses, fungi and other foreign antigens to enter the human body. In addition to this exogenous burden, there are also a large number of endogenous microbial flora parasitic in the oral cavity, teeth and mucosal surfaces, thus providing a large amount of antigenic stimulation to the host. Regarding microbial colonies, they can be divided into two major categories: the first category consists of bacteria in free form, mainly found in saliva, and the second category consists of bacteria in colony form, mainly found on dental plaque or mucosal surfaces.

Main components

The composition of saliva

The oral cavity is constantly bathed in saliva, a special secretion that contains a large number of antibacterial active ingredients and plays an extremely important role in maintaining oral health (1). These saliva-derived substances are usually proteins that are mainly synthesized in the large and small salivary glands (2), but a considerable portion also comes from the blood through the gingival crevicular fluid or directly from the polymorphonuclear cells (PMN) in the oral cavity (3). Generally, the antimicrobial substances in saliva are divided into non-immunoglobulin-intrinsic factors and immunoglobulin-acquired factors.

Bacteria in saliva

There are other important substances in saliva that indirectly act on pathogenic microorganisms and work synergistically with the antibacterial substances in saliva. These substances are some small molecule peptides, often called growth factors. Many studies have shown that there is a direct correlation between the concentration of growth factors in saliva and the receptors of growth factors on the surface of mucosal cells. These receptors are activated when biofilm bacteria attach.

Major antimicrobial factors and growth factors in human saliva

Non-immunoglobulin, endogenous factor

Lysozyme

Lactoferrin

Salivary peroxidase

SCN-

H2O2

Myeloperoxidase

Cl-

Lectins

Histidine-rich proteins

Proline-rich proteins

Mucin

Macrophages

Immunoglobulins, acquired factors

IgA (sIgA), IgG and IgM

Growth Factors

EGF : Epidermal Growth Factor

PDGF : Platelet-derived Growth Factor

TGF : Transforming Growth Factor

FGF : Fibroblast Growth Factor

IGF I&II: Insulin I&II Growth Factor

Past studies on the activity of OSCN produced by some antimicrobial factors such as lactoferrin, lysozyme, and lactoperoxidase systems have yielded mixed results. In fact, a single antibacterial substance cannot prevent the occurrence of periodontal disease. On the contrary, it is the synergistic effect of all these antibacterial substances, endogenous/acquired factors and growth factors that constitute an effective defense system against oral diseases.