Testing Salivary Flow

Mounting evidence points to the importance of clinical assessment of oral dryness,33,34 which is a significant predictor of salivary gland hypofunction.35 While the total volume of saliva varies per individual, the average daily production ranges from 1 to 2 liters per day. The flow rate for normal, unstimulated saliva is 0.25 to 0.4 ml/minute. A resting flow rate between 0.1 and 0.25 ml/min is considered low and less than 0.1 is considered very low.31,32

A simple way to determine stimulated salivary flow rate, is to have a patient spit into a cup while chewing a piece of sterile wax for five minutes. Normal stimulated whole saliva flow is 1 to 3 ml per minute; 1 ml/min-0.7 ml/min is considered low. Rates below 0.7 ml/min are considered very low.31,32

Visual inspection of the mucosa inside the lips can also aid in detection of dry mouth. Retract the lower lip. Dry the surface with gauze. Within one minute there should be many tiny drops of saliva if there is enough flow from the minor salivary glands that are located just under the mucosal surface. Those with enough salivary flow will also have saliva pooling in the floor of the mouth.31,32

There is a saliva-testing examination tool that contains six different tests. Clinicians can evaluate salivary production, viscosity and pH of resting saliva, quantity and pH of stimulated saliva, and buffering capacity. This testing can provide initial baseline data and can be used to demonstrate salivary stability or quantify changes over time.