Buffer systems in saliva are able to neutralize acids and thus contribute significantly to the natural protection against caries in the dentition. The extent to which this acid binding occurs is determined by buffer capacity determination. The buffers contained in saliva are mainly hydrogen carbonates, but also proteins and phosphates. The buffer systems are formed by the salivary glands during active mastication, so that they are present in significantly higher concentrations than in resting saliva. Thus, the ability of saliva to buffer acid attacks is also closely related to its flow rate. The buffering of acid plays a significant role in that the acid contained in saliva, whether it is a metabolic product of cariogenic bacteria in the plaque (dental plaque) or directly supplied by acidic foods or beverages, causes demineralization (decalcification, dissolution of mineral components) of the hard tooth substance. In a healthy oral environment that is not over-supplied with cariogenic and/or acidic foods for prolonged periods, demineralization is in balance with remineralization processes (re-storage of mineral substances). However, if acid exposure continues over a longer period of time, cavitation of the tooth, i.e. the formation of a hole in the previously demineralized area, is the consequence. Using hydrogen carbonate as an example, let us show how the hydrogen ions (H+) that make up the acid value are bound in a chemical reaction and consequently less is released:
HCO3 – + H+ → H2O + CO2
Here, water and gaseous carbon dioxide are formed. The more hydrogen ions are bound by the buffer systems, the less frequently the acidity of saliva falls below the critical values at which decalcification of the enamel (pH < 5.7) and the dentin of exposed tooth necks (pH < 6.3) occurs.
Indications (areas of application)
- Buffer capacity determination is a useful addition within the overall caries risk determination options for a patient who does not have carious lesions (anymore).
- Like any method that leads to the visualization of test results, the buffer capacity determination contributes to the patient’s motivation in a very vivid way.
Contraindications
The use of the procedure is not indicated before sanitation of already diagnosed carious lesions, because the buffer systems must be to some extent permanently active due to the content of acid-forming bacteria in the existing cavitations (holes). Reliable comparisons can only be made after remediation and in the context of subsequent follow-up controls.
Before the examination
Before the buffer quality of saliva can be determined, a saliva sample must first be collected. This is usefully done as part of a saliva flow rate determination, 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. Since one wants to get comparable results over longer periods of time, the following recommendations exist from the manufacturer’s side (KariesScreenTest by Aurosan), which refer to at least one hour before the test:
- Do not eat
- Drink nothing
- Do not chew gum
- Do not smoke
- Do not brush teeth
- Do not use mouth rinses
The procedure
The test for buffer capacity determination (e.g. CRTbuffer) is fast and requires little effort:
- A small amount is taken from the previously collected saliva sample using a pipette and applied to a test strip loaded with an indicator system.
- Excess saliva is removed by an absorbent pad.
- After five minutes, the elapsed color change is compared with a reference scale and allows subdivision into three categories:
| Color change | Buffer capacity |
| Yellow-brownish | low, pH < 4.0 |
| Greenish | medium, pH 4.5 to 5.5 |
| blue | high, pH > 6 |
After the examination
Only several diagnostic procedures in their entirety contribute to making realistic statements about a patient’s caries risk to be expected in the further course.The determination of buffer capacity should therefore not be used solely for prognostic purposes. Rather, it should be viewed in addition to findings that are available on the following clinical and other salivary diagnostic parameters, among others:
- Assessment of oral hygiene
- Assessment of dietary habits
- Assessment of caries experience (already gone through carious dentition damage).
- Presence of carious initial lesions (visible whitish decalcification).
- Determination of the salivary flow rate
- Saliva test for Streptococcus mutans
- Saliva test for lactobacilli
