Saliva Test for Lactobacilli

Evidence of excessive salivary contamination with lactobacilli is considered an indication of increased caries risk, as these are among the most important germs driving caries along with Streptococcus mutans. In addition to the most important caries-causing germ Streptococcus mutans (S. mutans), a number of other plaque bacteria (bacteria in dental plaque) are involved in the caries process, including lactobacilli. Although their involvement in the development of caries in tooth enamel is probably less than was previously assumed, they are particularly responsible for the demineralization of dentin (dissolution of mineral substances from the dentin). On the one hand, the number of lactobacilli can be used to draw conclusions about a patient’s sugar consumption, and on the other hand, they are an indication of open carious lesions that have already penetrated the dentin. Thus, a low test result suggests a low-sugar diet and a presumably (dentin-) caries-free dentition, whereas if the bacterial count is high, the dietary pattern may carry a caries risk due to high sugar consumption and a search should be made for an untreated carious dentin lesion.

Indications (areas of application)

The indication for testing saliva for excessive lactobacilli load arises in the context of individual prophylaxis:

  • Establishment of an individual prophylaxis program; the results of the saliva test are incorporated into the recommendations that the patient receives for fluoridation measures, dietary changes and recall intervals (interval between dental visits).
  • Follow-up of individual prophylaxis
  • Progress control in the presence of carious initial lesions in the enamel area, which have not yet penetrated into the dentin. If the value increases significantly in the course of recall (the regular control examinations), this may be an indication that the caries has penetrated further into the dentin and can no longer be brought to a halt by prophylactic measures.

Contraindications

  • Saliva testing for lactobacilli should not be performed during or within two weeks of antibiotic therapy.
  • An antibacterial mouth rinse must not be used in the 12 hours before saliva collection.

Before the examination

First, a saliva sample is collected, usefully in conjunction with a determination of the saliva flow rate, for which the patient chews on a kerosene pellet for five minutes and collects the resulting saliva in a cup. The amount produced allows conclusions to be drawn about the natural cleansing ability of saliva by rinsing the teeth. The saliva sample can also be used to determine the buffer capacity of the saliva, which, like the amount of saliva produced, allows conclusions to be drawn about the caries susceptibility of the dentition. Since one would like to get comparable results over longer periods of time, the following recommendations exist from the manufacturer’s side (KariesScreenTest by Aurosan), which refer to the behavior at least one hour before the test:

  • Do not eat
  • Drink nothing
  • Do not chew gum
  • Do not smoke
  • Do not brush teeth

The procedure

From the company Aurosan easy-to-use, double-sided coated culture media in sample tubes are offered (KariesScreenTest):

  • The carrier side coated with blue agar (culture medium) is used for the bacterial count test of S. mutans.
  • The carrier side coated with light agar is used for the bacterial count examination of lactobacilli.
  1. The agar carrier is taken from the sample tube.
  2. A NaHCO3 tablet is placed on the bottom of the tube. The sodium bicarbonate releases CO2 (carbon dioxide) during the incubation period of the saliva sample and thus ensures a low-oxygen atmosphere.
  3. The protective films are removed from the agar surfaces without touching them.
  4. Saliva is applied to the agar surfaces with a pipette, excess saliva is allowed to drip off by holding it at an angle.
  5. The tube is sealed after insertion of the agar carrier.
  6. Incubation of the upright sample is performed in the incubator cabinet for 48 hours at 37 °C. An incubation period extended by one to two days does not affect the number of germ colonies.
  7. Reading of colony density is done visually by comparison with a reference map. The classification is only in two risk classes:
Risk class CFU (colony forming units) per ml saliva
Low < 105
high > 105

After the examination

The incubated culture media can be used as visual aids in motivational talks with the patient and can be an important argumentation aid for switching to a tooth-healthy diet.