SCIENCE

This is your mouth on acid

Betty Zou, Ph D.

A puckered mouth is an easy way to spot someone who’s eaten a piece of not quite ripe fruit or sour gummy candy. But beyond the characteristic facial expressions, acidity can have other, less amusing effects on your mouth.

The average pH in a healthy mouth is around 7.3. (pH is the scientific scale on which acidity is measured with 7 being perfectly neutral and anything below 7 being acidic.) That’s not to say that the pH in your mouth remains at 7.3 all the time. There are large fluctuations throughout the day caused by eating and drinking, dental hygiene and even your body’s natural daily rhythm. For example,the pH in your mouth drops slightly during sleep when there is less saliva flow.

Why should you care about mouth acidity? For starters, it is both an indicator of and contributor to overall oral health.

A frequently acidic oral environment can put you at risk of tooth decay and cavities. The cause is two-fold. First acid erodes tooth enamel.When the pH inside the mouth drops below 5.5, the hard protective coating on teeth start to dissolve. With time, acid erosion can change the color, shape and length of teeth, causing them to become brittle and transparent. One consequence of acid erosion is tooth sensitivity. Without the enamel shield, the nerve endings underneath are exposed to the hot and cold of the food and drinks we consume. This is what causes the sharp tooth pain that can accompany a glass of iced tea. Loss of tooth enamel also exposes the vulnerable underlying tissues to harmful oral pathogens, giving those bacteria greater opportunities to take root and cause disease.

Which leads us to the second reason why mouth acidity is damaging to oral health: bacteria. Most bacteria, including the beneficial microbes that help maintain good oral health, prefer to live in a pH neutral habitat. The notable exceptions are the disease-causing bacteria like those that are responsible for cavities and gingivitis. These destructive microbes thrive when the pH drops and their competitors die off.

So what causes oral pH to decline? The most obvious explanations are acidic food and drinks like citrus fruits, fruit juices and soda. How you drink these beverages matters too. Studies have shown thatthe so-called long sipping method, where you sip from a glass for 15 minutes, causes only a modest drop in pH but takes the longest to recover. In contrast holding the drink in your mouth for two minutes before swallowing led to the sharpest drop in pH.

Medical conditions can also contribute to mouth acidity by causing stomach acid, which can range from pH 1.5 to 3.5, to enter the mouth. This could be due to gastroesophageal reflux disease (GERD), which also leads to heartburn and acid indigestion, or frequent vomiting related to morning sickness or eating disorders, for example.  

Instead of avoiding citrus foods and juices entirely (and potentially putting yourself at risk of scurvy), wait at least 40 minutes to an hour after eating or drinking to brush your teeth. This will give your enamel enough time to harden after the acid exposure and reduces the damage that can occur with brushing softened tooth enamel. Rinsing your mouth with water will also help to remove residual acids, whether from food or gastric contents, from the oral cavity. If a sweetened beverage is what you’re after, look for something like qii that has a close to neutral pH because when it comes to acid in the mouth, less is definitely more.

Betty Zou, Ph D.

Scientist turned science writer and communicator. I turn complex scientific concepts and studies into clear and engaging content for diverse lay audiences. Previous work include blog posts, news articles and releases, patient and customer profiles, feature length stories, donor reports and marketing materials. My areas of expertise are molecular biology, microbiology and microbiome-related topics but I have also written extensively about other health and medicine topics such as cancer, cardiology and trauma.

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Dental plaque is made up of millions of bacteria that live in a sticky film on the surface of teeth. This microbial community is also referred to as a biofilm. To study the effectiveness of qii in reducing dental plaque, we tested it in the lab against the oral pathogens Streptococcus mutans(tooth decay and cavities), Porphyromonas gingivalis (gingivitis) and Solobacterium moorei (halitosis).

A good oral hygiene regimen can help eliminate plaque, one of the main contributors to oral conditions like tooth decay and gum disease. We’ve developed qii, the world’s first drink proven to reduce plaque buildup because let’s be honest, we don’t always floss and brush our teeth as often and as diligently as we should.