Why does my breath smell bad even after brushing?

Brushing and flossing are essential parts of daily oral hygiene. Yet, even after brushing and flossing, some people still experience bad breath. This article will investigate why bad breath can persist even after an oral hygiene routine.  

Causes of bad breath

Oral bacteria 

Our mouths are filled with bacteria, fungi, and viruses – collectively called our oral microbiome. They mostly keep us healthy, aiding digestion, fending off infections, and reducing blood pressure. But some species are harmful and release byproducts that lead to bad breath, cavities, gum disease, and other oral conditions. Certain species break down proteins in our diet and release "volatile sulfur compounds" (VSCs), which have an unpleasant odor. The more of these species we have in our mouths, the higher levels of VSCs they produce. 

VSCs have foul odors and include hydrogen sulfide (which has a rotten egg smell) and methyl mercaptan (which has a rotten cabbage smell). When VSCs build up in our mouths, they are picked up as we breathe and speak, giving our breath a bad smell.

One reason your bad breath may not subside after brushing and flossing is if the source of bad breath is not the bacteria on your teeth and gum line. While the gum-line is a hotspot for the bacteria that cause bad breath, these bacteria can also build up in different mouth areas, including the tongue, tonsils, and stomach. 

Bacteria on the tongue

The most common home for bad breath-causing species is on the tongue, especially the back of the tongue near the throat. As bacteria settle and grow there, they will assemble into a "biofilm" (slimy community of bacteria) on the tongue leading to tongue coating. A study of 2000 individuals with halitosis found that 43% experienced tongue coating. The tongue is covered with tiny hair-like structures called filiform papillae, which form an ideal hiding spot for these bacteria. Like bugs in a deep rug, the bacteria can hide between these papillae and continue thriving. Even after tongue cleaning, such as using antiseptic mouthwash, microbes that cause bad-breath can colonize and replicate quickly, especially in the case of oral microbiome dysbiosis.

Tonsilloliths (Tonsil stones)

Another place halitosis-causing species have been in our tonsils. They'll form a community (biofilm) that can, over time, harden into "tonsil stones" (also called tonsilloliths) that attach to our tonsils and cause a lingering bad odor in the mouth. 

Dry mouth

Another common reason for bad breath is dry mouth. A study comparing salivary flow rate (the amount of saliva we produce) and the level of VSCs found that people with very low levels of saliva had significantly raised levels of VSCs and were more likely to have tongue coating than people with regular salivary flow.

Bacteria can typically only survive in our mouth if they are able to settle and colonize (in a biofilm). Saliva contains proteins that kill bacteria and act as a natural rinse to remove them. These proteins include lysozymes that attack bacteria's cell walls and antibodies that prevent bacteria from settling in our mouths. 

Saliva also helps promote helpful bacteria that in turn defend us against harmful species. Saliva provides nitrate from our diets to feed these beneficial bacteria, called nitrate-reducing species. These species have been found to naturally release low levels of hydrogen peroxide and other byproducts which kill the bacterial species that cause halitosis and gum disease. 

When we sleep, our saliva flow is dramatically reduced, which is one reason why bad breath is most common when we first wake up (often called "morning breath". Other causes of dry mouth include certain medicines, drinking alcohol, dehydration, and missing meals (the act of chewing increases saliva in the mouth). 

Helicobacter pylori infection

Another source of halitosis may be the presence of the bacteria H. pylori in your gut or oral microbiome. A review of 21 studies found that H. pylori infection correlates with halitosis. H. pylori has been found to be able to produce VSCs, but more research is needed to establish a direct causal relationship between it and bad breath. Up to two thirds of the population is colonized by H. pylori, and in rare cases it causes gastric ulcers, which are correlated with halitosis.

Gastroesophageal reflux disease (GERD)

Gastroesophageal reflux disease (also known as GERD or acid reflux) occurs when stomach acid frequently moves up through our throat and digestive tract. This backwash can irritate the lining of your throat.

Studies have suggested that GERD may increase a person's risk of halitosis. This could be due to an accumulation of postnasal drip on the back of the tongue. In GERD, acidic stomach contents have been found to reach the top of the throat and irritate the walls of our throat, resulting in postnasal drip.

Another explanation is that gases from our stomach and digestive tract may be released through the throat due to a damaged lower esophagus, typically responsible for limiting these contents from coming up from the stomach.   

Brushing and flossing incorrectly

We all know that we are supposed to brush our teeth twice a day and floss, but many of us are not using the correct brushing and flossing technique, which may be why bad breath bacteria are persisting. Below is an overview of the correct brushing and flossing technique:

How to brush correctly (Modified Bass technique)

• Use a pea-size amount of toothpaste.
• Hold your toothbrush at a 45-degree angle, like below. This is the best angle for cleaning both the surface of your teeth and inside the gumline (killing two birds with one stone).
• Move the toothbrush in a small circular motion. This motion has shown to be more effective at cleaning teeth while being less harsh on our enamel (compared to a back and forth motion)
• Repeat on the inside of your teeth
• Continue for 2 minutes.
• Brush or clean your tongue
• Spit, but wait to water rinse
• Change your toothbrush every 3-4 months.

How to floss correctly

Most of us avoid flossing daily (with 20% avoiding entirely), and one-third of people say they would rather sit in gridlock traffic than floss. This is an issue because brushing only cleans ~60% of your mouth, and flossing picks up the remaining 40% on the inner surfaces of our teeth. Our internal research has also found flossing reduces the levels of gum disease and bad breath-causing bacteria. 

If you hate flossing because it causes bleeding, you are probably using the wrong technique. When done correctly, flossing should be painless and prevent gum bleeding over time by reducing inflammation.

Here's how to floss the proper way with the C-Shape technique:

• Take a length of 12 to 18 inches of floss and wrap it around both of your index fingers.
• Next, gently move the piece of floss back and forth to guide it between your teeth.
• Wrap the floss around the side of your tooth in a C-shape, and gently guide it up and down the length of your tooth and softly into your gum line
• Note: plaque is soft, so it does not require much force to remove it
• Repeat for the other side of the tooth and for all other teeth, moving along your section of dental floss to keep using a clean piece of floss
• In total, it should take about 1 to 2 minutes.

Common mistakes

• Applying too much pressure. Placing too much pressure on the floss may cut your gums, which is more harmful as it allows bacteria to enter your bloodstream.
• Moving straight up and down without wrapping the floss. The dental floss has to touch the inside of your teeth to properly remove the plaque/food debris.
• Not flossing for extended periods. Incorporating daily flossing into your routine may be tedious at first, but it gets easier over time. 

Ways to Get Rid of Bad Breath

There are a number of ways to address bad breath beyond brushing and flossing, including:

Tongue cleaning or tongue scraping

• Regular tongue cleaning with a tongue scraper has been found to reduce the levels of VSCs in people with bad breath by 30-75%.

Using a mouthwash or Mouth Rinse

• Academic reviews have found that mouthwashes containing chlorhexidine (CHX), cetylpyridinium chloride, and zinc effectively reduce bad breath symptoms. After three and six months, people using the zinc acetate/CHX rinse showed significant reductions in their levels of VSCs.
• However, prolonged usage of CHX mouthwash has potential disadvantages, including staining of the teeth and tongue, a metallic sensation after use, or reduced taste perception. 
• These approaches simply reduce the abundance of all bacteria and can kill the diversity of the oral microbiome. Bad breath sufferers can consider mouthwashes as a short-term solution when used with other oral hygiene recommendations, but likely not a long-term fix.

Taking oral probiotics

• Multiple studies have measured the effectiveness of probiotics in reducing symptoms of bad breath and VSC-releasing bacterial species and found promising results.
• The most commonly studied effective oral probiotic species are S. salivarius strains K12 and M18 in a culture. 
• Studies have found oral probiotics to be most effective when combined with tongue-scraping and good oral hygiene practice.

Increasing saliva production

• If your bad breath is coming from dry mouth, there are several options you can consider to increase your saliva production. These include chewing sugarless gum, xylitol gum, and xylitol lozenges.
• Xylitol-containing mouthwashes like Biotene Dry Mouth Oral Rinse or ACT Total Care Dry Mouth mouthwash support saliva production and reduce bad breath odors. Xylitol is a naturally occurring sugar alcohol found in plants, including many fruits and vegetables, that has been found to reduce the abundance of harmful and odor-causing bacteria in our mouths, in turn preventing bad breath and tooth decay.

Maintaining a proper diet

• Proper hydration further helps to stimulate the production of saliva and removes food particles and food debris from our mouths that feed VSC-producing bacteria. So be sure to drink plenty of water throughout the day to keep your mouth moist.
• Raw fruits and vegetables that are high in fiber also reduce disease-causing bacteria, while yogurt can effectively promote beneficial bacteria and lower levels of VSCs.
• The most highly recommended foods are nitrate-rich vegetables like spinach, lettuce, fennel, radishes, and beets. These act as prebiotics and increase the levels of beneficial bacteria in our oral microbiome.
• The consumption of alcohol, caffeine, and mouthwashes that contain alcohol also leads to dry mouth. Reducing the intake of these substances can also improve oral health care and overall health. 

How to determine what is causing your bad breath

Since bad breath can come from several different sources, it can be difficult to determine which treatment and approach will be most effective in treating it. Here are some ways you can identify the source of bad breath:

Ask your dentist or oral health professional to check for tonsil stones

• Dentists will be able to do a routine check for tonsil stones and can assist with removing them if it's found that you have them.

Test your oral bacteria

• Since over 90% of bad breath cases originate in the mouth, testing your oral bacteria is a great first step for identifying if bad breath is coming from VSC-producing species. 
• The Bristle Oral Health test analyzes your saliva to measure the levels of your good bacteria and those that cause bad breath and gum disease, then matches you with a treatment plan based on your results.

Test for H. pylori

• Several tests and procedures are used to determine if you have H. pylori infection.Tests may be done using a stool sample, through a breath test, and by an upper endoscopy exam.