pH of saliva

On average, the pH of saliva approaches neutrality, oscillating between 6.5 and 7.4 thanks to the precious buffer action of the bicarbonates it contains. As a rule, in men the salivary pH is slightly more acid than in women. Positive and negative variations are however quite frequent and physiological in most cases. The pH of saliva is in fact influenced by the degree of oral hygiene, the type of diet but also by morbid factors. Regardless of the cause, acid saliva is an important risk factor for caries, erosion of tooth enamel and dentinal hypersensitivity. The critical value of the salivary pH, below which enamel is demineralised, is 5.5. On the other hand, even a saliva pH that is too alkaline is the enemy of the teeth, since it favors the deposition of the mineral salts present in the saliva and in the food, so that the bacterial plaque is mineralized more quickly forming the tartar.

Thanks to the presence of bicarbonates, saliva is in fact a buffer system that corrects the acidity of the oral cavity following the intake of particular foods (grapefruit, fruit salads, oranges, lemons, cold teas, orange juice, juices, beverages sodas, tomatoes, etc.) or drinks. Those diuretic, like coffee and alcohol, reduce the secretion of saliva, with a consequent increase in oral pH; caffeine also stimulates the production of gastric acids and can aggravate gastroesophageal reflux, which in turn helps to significantly lower the salivary pH. In general, therefore, the pH of the saliva drops when the secretion is scarce and moves towards the alkalinity when the salivary secretion is abundant (for example in coincidence with the so-called "mouth watering", triggered by perfumes, images and other sensations that evoke a welcome food). We also remember that the saliva has a mild antibacterial effect, thanks to the presence of thiocyanates, hydrogen peroxide, glycoproteins, immunoglobulins and especially lysozyme.

The Stephan curve shows the trend over time of the pH of the saliva following the intake of food (especially carbohydrate); examining this curve, we note how the salivary pH remains acid from 5 to 20 minutes from food intake, a period in which the risk of carioreception is maximum. In this period it is important to intervene with adequate oral hygiene or better still with generous rinses based on simple water. Brushing your teeth in this period of time, especially if you do not use soft brushes and delicate toothpastes, can in fact promote enamel demineralization.