I frequently see patients who regularly make their cleaning and exam appointments, demonstrate good oral hygiene but for some reason have an ongoing history of getting cavities. When oral hygiene standards and professional checkups are being met there may be a less obvious cause... Saliva. Salivary plays an integral role in the health of our teeth and oral tissues. Patients may unwittingly be affecting the quality or quantity of saliva through habits or activities.
Saliva functions to buffer the oral pH to its normal range around neutral (7) and contains components that also protect the teeth from bacteria build up. Saliva is part of our immunity and immune defense. It has antibodies that can be the first line of defense against viruses and bacteria. Enzymes in our saliva like lipases and amylases provide the first step in digestion by beginning the breakdown of starch and fats in our mouth while we are chewing. There are other proteins in our saliva that act with the electrolytes to buffer the pH against acids.
The pH of saliva plays a large role in the rate of cavities for an individual. When the pH is acidic the teeth demineralize, lose minerals and become softer this allows bacteria to grab on to the teeth and stick better. The pH in our mouths fluctuates normally while eating and doing certain activities and saliva provides the minerals needed to strengthen and harden the teeth again as well as help return the pH to normal. When the oral environment is chronically acidic however the softer tooth surface allows adhesion of bacteria and eventual infiltration (a cavity). The acidic environment is also more favored by the bacteria that cause both cavities and gum disease so a more neutral pH inhibits overgrowth of “bad” bacteria that cause periodontal disease and cavities.
There are certain things we can do to keep the pH of our saliva in the healthy range but first it's important to know which conditions cause a reduced pH. One activity that we all partake in is consuming foods and beverages. The pH in the mouth will drop when eating any food or beverage. That’s because acids in food and beverages can cause a significant drop in pH that takes the mouth time to rebound from. When the pH in the mouth drops below 5.5 teeth begin to lose minerals and soften a process called demineralization. Each time we consume any food or beverages the pH in our mouths drops and it takes a minimum of 20 minutes after eating for our saliva to return to healthy levels. This is why you should wait at least 20 minutes after eating to brush your teeth, the 20 minutes allows the teeth to “harden” (or re-mineralize) while the pH recovers. It is important to note that food that is highly acidic for example soda, energy drinks, or citric juice it could take longer than 20 minutes for pH to recover. Energy drinks have a pH ranging from 1.5-3.3 (stomach acid has a pH of 1.5-3.5). Full sugar sodas have pH’s ranging from around a pH of 2- 2.5 and even diet sodas have a pH of 3.0-3.2. This is dramatically worse in patients who sip on soda or energy drinks during the day (also those who snack throughout day). Frequent sipping or snacking doesn’t usually allow the 20 minutes or more for pH recovery in between acid exposure. Therefore in these individuals their oral environment could be acidic for hours or even the majority of the day. This will lead to long term damage to enamel (namely loss of enamel, teeth becoming more translucent and yellow) and a significant increase in cavities compared to individuals who do not snack. It's best to eat at designated times during the day and not throughout the day.
So how can someone enjoy the occasional acidic beverage? Having a soda all at once with a meal is better for your teeth than sipping for an hour. With the meal the mouth has dropped pH from the food as well and can recover, sipping for an hour keeps the pH in the acidic range for that whole period. Avoiding acidic beverages that aren’t natural is the smartest choice when it comes to protecting your teeth. In fact water is the best choice since it is within the range of our natural pH. Coffee is best finished in one sitting and not sipped on throughout the day. Fruit juice should always be avoided due to the high sugar content and high acidity. The pH in our mouths drop less significantly when eating fruit whole because fruit’s natural fiber acts to prevent direct acid exposure to the teeth. Sodas, flavored and natural juices all contribute to increase in tooth decay.
I am finding more and more patients have been choosing energy drinks every day over coffee for their caffeine intake. I urge my patients to avoid energy drinks at all costs because of their extremely acidic pH. Energy drinks have the pH of stomach acid (1.0-3.3) while black coffee has a pH of 5. Redbull and Monster Energy drinks have a pH of 2.7, while Rockstar energy drinks have a pH of 1.5. Some individuals drink one of these every day! Yes coffee is still acidic and best consumed all at once however it's less of a difference between our natural pH meaning our mouths can recover more quickly.
Coffee isn’t without blame though. Coffee is a very common source of decay in adults. Many people add milk and sugar to coffee and sip it throughout the day. Over years these patients begin to develop cavities in between their teeth, even with adequate oral hygiene. Great oral hygiene can’t out-compete repeat acid exposure day in and day out. The best advice for protecting your teeth against the acid in coffee is to have it with a meal or at least have it all in one sitting. Opt for sugar alternatives or drink it black when possible.
Ok so food is a fairly obvious factor in our oral pH but what else can affect it? The answer is systemic inflammation. Any kind of systemic inflammation also affects the oral environment. Studies have found sleep deprivation, tobacco use, medical conditions such as diabetes lead to saliva with a low pH.
What causes a decrease in salivary production? Certain physical activities, differing states of hydration, drugs and medications can affect salivary flow. Everyone experiences increases and decreases in salivary flow throughout a given day through our normal activities. Aerobic exercise will cause a decrease in salivary flow as our sympathetic nervous system becomes more activated. Less energy is going to salivary flow and digestion. Once a person stops exercising the parasympathetic system can come back “online” and resume these functions. Stress and dehydration can cause temporary decreases in salivary flow. Many medications can cause dry mouth including blood pressure medication, anti-anxiety medications, antidepressants, antiemetics, antiepileptics, antihistamines so it’s important to check the side effects of all medications in order to curb the effects of medication induced dry-mouth. Systemic medical conditions can cause dry mouth including. Sjogren’s disease which is an inflammatory disorder causes decreased salivary gland function (along with other glands including tear ducts) that can worsen with time. Lupus as well as hypothyroidism has been associated with decrease in salivary flow and hyposalivation. Other inflammatory diseases such as Rheumatoid arthritis, Diabetes Mellitus II causes dry mouth due to systemic inflammation and dehydration. Another thing to note with patients with diabetes, the dry mouth combined with the high blood sugar creates an environment for thrush (a fungal infection) to take hold, and it’s something we are always looking out for in these patients.
Our biggest dental concern with our xerostomia patients is an increased rate of decay. They are known to get more cavities more often than patients with normal saliva production. Keep in mind which activities worsen xerostomia and avoid them if possible. Excessive caffeine, chronic use of antihistamines, foods with high salt or high sugar content all will lead to dry mouth. Drink lots of water throughout the day and to avoid decay opt for sugar alternatives when possible. A healthy diet, with good sleep hygiene will help decrease systemic inflammation which in turn will help with xerostomia that is caused by inflammation. A humidifier at night can help with xerostomia while sleeping or working. An added step to prevent decay in patients with dry mouth is the use of Xylitol (which inhibits the growth of cavity causing bacteria). There are Xylitol tablets that adhere to the cheek tissue to help deliver the cavity fighting compound throughout the night. MI paste uses “recaldent”, a compound that has been shown to provide very effective re-mineralization of teeth over time. Custom trays can be made for these patients and they can add a little MI paste to these trays and pop them in before bed. These added steps for decay prevention make a significant difference in individuals with xerostomia. Unfortunately there isn’t a lot that can be done to consistently increase salivary production in these individuals. Sugar free candies with xylitol can increase saliva secretion but it may not be sufficient for relief. Even with doing all of these things xerostomia may not significantly improve and saliva substitutes should be employed to prevent drying of teeth and tissues. For patients with xerostomia it becomes very important to not miss routine cleanings and dental exams.
Saliva composition, volume and pH play a critical role in oral health. Identifying behavior or factors in our lives that can affect these attributes as well as utilizing methods to prevent our counteract these deficiencies are important for maintaining good oral health.