Saliva is a complex biological fluid produced by three major pairs of salivary glands and numerous minor glands throughout the mouth. Composed primarily of water, it also contains electrolytes, proteins, enzymes, and antimicrobial agents. This dynamic biological solution provides the primary defense for the teeth and soft tissues against constant threats in the oral environment. Maintaining a steady flow of saliva is foundational to protecting overall oral health.
Mechanical Cleaning and Lubrication
The continuous flow of saliva acts as a natural rinse for the oral cavity. This flow physically washes away debris, including food particles, residual sugars, and bacteria from the surfaces of the teeth, tongue, and gums. This flushing action limits the time fermentable carbohydrates are available to oral bacteria, reducing the formation of dental plaque.
Saliva contains specialized proteins called mucins, which give the fluid a viscous quality. Mucins create a protective, lubricating layer that coats the soft tissues of the mouth, including the cheeks, tongue, and gums. This layer significantly reduces friction, protecting delicate tissues from mechanical trauma during speaking, chewing, and swallowing. Without this lubrication, the inner surfaces of the mouth would become dry, irritated, and susceptible to injury.
Neutralizing Acids and Maintaining pH
The primary threat to tooth enamel comes from acid produced by oral bacteria after consuming sugars. When bacteria metabolize carbohydrates, they release organic acids, causing a rapid drop in the mouth’s pH level. If the pH falls below 5.5, the tooth enamel begins to dissolve in a process known as demineralization.
Saliva contains potent chemical buffering systems designed to rapidly counteract this acidic environment. The most effective is the bicarbonate buffer system, which is secreted in high concentration when saliva flow is stimulated, such as during eating. Bicarbonate ions chemically react with the acid, neutralizing it and quickly raising the pH back toward a neutral level. The phosphate buffer system also contributes to this neutralization, stabilizing the oral environment against acid attacks.
The Essential Process of Enamel Repair
Even with the action of buffering systems, some mineral loss from the tooth surface occurs during an acid challenge. Saliva is uniquely formulated to reverse this loss because it is naturally supersaturated with the building blocks of tooth structure, maintaining high concentrations of calcium and phosphate ions.
When the oral pH returns to a neutral state, these minerals are redeposited onto the compromised areas of the enamel surface. This process, called remineralization, effectively repairs microscopic lesions before they progress into visible cavities. Saliva supplies the necessary calcium and phosphate to rebuild the crystalline structure of the enamel. Salivary proteins also transport these ions and regulate the formation of new mineral on the tooth surface.
What Happens When Saliva Production Decreases
When salivary glands fail to produce adequate fluid, a condition known as xerostomia, or dry mouth, occurs, severely compromising all protective functions. Common causes include side effects from medications, systemic diseases like Sjögren’s syndrome, and radiation therapy to the head and neck. The absence of sufficient saliva leads to severe consequences for oral health.
Without mechanical flushing, plaque accumulates rapidly, increasing the concentration of acid-producing bacteria. The lack of buffering capacity means the mouth remains acidic longer after eating, accelerating enamel demineralization. This often results in rampant tooth decay, particularly affecting the roots of the teeth. Furthermore, the loss of the lubricating film makes soft tissues vulnerable to chronic inflammation, increasing the risk for gum disease and oral infections like candidiasis.