Modern dentistry can predict the appearance of caries by means of diagnostic studies of saliva.
In determining the risk of developing caries helps to study saliva: its microbiological composition, pH, buffer capacity and viscosity.
Microbiological analysis of saliva
Microbiological analysis helps determine the number and type of bacteria in the saliva, namely, acid-forming streptococci (Streptococcus mutans, Str. Sanguis, Str. Mitis, Str. Salivarius) and lactic bacteria (Lactobacteria). Despite the many other bacteria in the oral cavity, they are considered to be the main culprits of caries.
Three hours before picking saliva for analysis it is impossible to brush your teeth, rinse your mouth, eat food, chew gum.
For analysis on Streptocuccus mutans, a soft plaque or saliva test is taken. The investigated material is applied to a slide glass, which is placed in a special broth and incubated for two days at 37 degrees. Then the concentration of the grown colonies is read and compared using tables per ml of saliva. By the number of Streptococcus mutans, the individual risk of caries is determined.
Before testing for Lactobacteria, stimulate the secretion of saliva in the patient by chewing a fraction of paraffin in a minute. Then the saliva is placed on the slide with the nutrient medium. Excessive saliva from the glass is removed, and the sample is placed in a container.
The incubation period is four days at 37 degrees. After that, the colonies on the glass are compared to the standard on the table. The amount of lactobacilli is determined by the diet and consumption of carbohydrates (sugar).
Knowing the state of microbiocenosis in the oral cavity can reduce the risk of not only caries, but also chronic periodontitis, gingivitis, stomatitis.
Determination of the acidity of saliva
The degree of acidity of the liquid is determined by the pH-index. The average indicator - its neutral value - is 6.4. The pH of the saliva changes all the time due to nutrition, the activity of the microflora of the oral cavity, etc. If the pH is below the average (eg 5.6), there is an acidic environment, and the risk of developing caries is increasing.
The acidity of saliva is determined using potentiometry, using the electronic device (pH-meter) at the same time. One and the same sample are examined three times, after which the average pH is calculated. In most cases, the reaction of the medium ranges from 6.8 to 7.4.
Buffer capacity of saliva
Chicken and alkaline buffer capacity of saliva are determined after calculating the pH of saliva.
It shows how saliva is able to neutralize acids and perform a protective function in the oral cavity.
To some volumes of saliva (1.0 ml) add in the first case an equivalent volume of hydrochloric acid, and in the second - a solution of alkali. In both cases, the pH reading is measured and the buffer capacity of the saliva is calculated.
Determination of viscosity of saliva
The saliva is collected in a special sterile test tube. It should be collected at the same time in the morning after 1.5-2 hours after breakfast. The analysis is taken three times. Necessary for research quantity - from 2 to 12 ml.
The viscosity of saliva is investigated using a special device - Oswald viscometer or VK-4 capillary viscometer.
In the course of the study, the time of passing between the two labels of the apparatus initially distilled water, and then saliva, is calculated. Then the conclusion is drawn. If the viscosity of saliva increases, then the risk of tooth decay by caries increases.