True or False: Clearance of carbohydrates and microorganisms from the mouth to the digestive tract depends on salivary flow rate and site.

• A. True
• B. False
• C. Not sure
• D. Both A and B

Answer: (A)

Think of the mouth’s self-cleaning as a combination of how much saliva is produced and where the substances are located. Saliva flows rinse away sugars and bacteria and also help dilute acids; when the flow is high, substrates and microbes are swept out more quickly toward the swallow and onward to the digestive tract. Conversely, when flow is low, fluids move more slowly, allowing carbohydrates to stay in contact with teeth and biofilms longer, which promotes fermentation and acid production by resident bacteria.

The place where carbohydrates or microorganisms reside matters because some sites are readily exposed to saliva and swallowing, such as the surfaces of the tongue and the cheeks, while others are sheltered—within dental plaque, pits and fissures, or subgingival areas—where saliva has less access. Submerged or protected sites clear more slowly, while exposed sites clear more rapidly. So the statement is true: clearance depends on both how much saliva is flowing and where in the mouth the materials are located.