One of the most important factors influencing the progression of dental erosion is saliva, especially in our age of polypharma. Even before an acid attack takes place, saliva flow is often increased as a response to stimuli such as smell or chewing. A high saliva flow rate helps increase buffering, dilution and clearance of acids from the mouth, which is extremely important during an erosive acid challenge. A low salivary flow rate can have a number of negative effects. Saliva flow can be inhibited as a side effect to numerous medications, both prescription and over-the-counter. Medical conditions, such as xerostomia, dehydration, and salivary gland dysfunction can all put teeth at risk for erosion.36
The average adult in the US, over the age of 65, takes six or more prescription medications. Many of these medications have the potential to adversely impact saliva, or salivary flow rates, which can increase the risk of dental erosion. Low levels of saliva can impact the rate of pellicle maturation, and could also result in elevated risk of erosion due to excessive tooth brushing, chewing hard foods and bruxism. At the very least, changes in the saliva can make the process of dental erosion and toothwear much more complex.37
In older populations, where there is a combination of hyposalivation and polypharma, this can be a significant problem. These individuals can be exposed to very low pH acids in their mouth. When people are asleep at night, they only have about one-tenth of the saliva they have during the day. If someone is over 65, they likely have only half of the saliva they had when they were 20. Without sufficient saliva, it is difficult to provide sufficient buffering and clearance of acids, particularly if the patient suffers from acid reflux.
The chemical composition and buffering capacity of saliva are also important factors. If saliva has a high concentration of bicarbonate, it has an increased capability of neutralizing and buffering erosive acids, and if supersaturated with respect to calcium and phosphate, it is better equipped to reverse low levels of initial softening that might occur. Saliva that is undersaturated with respect to calcium and phosphate has little ability to help protect tooth surfaces against erosive acid challenges.38