Sometimes tooth sensitivity or bad breath are just symptoms of a flu bug that will go away when your flu does. But sometimes, these symptoms that show up in the mouth are the body's way of letting you know that something much more serious is going on elsewhere in the body.

How to know when it's serious and when it's not?

Know these dental symptoms that you should never ignore and when to see your dentist:

1. Bleeding Gums
Your gums act like a gasket, sealing the spaces between teeth so food doesn't accumulate and bacteria can't invade the jawbone -- and the rest of your body.

Bleeding gums are an indicator for gingivitis or -- if the gingivitis is left untreated -- periodontitis, which is a serious infection that can lead to teeth loosening or even falling out. Both gingivitis and periodontitis are diseases caused by inflammation in the mouth due to plaque build-up along the gumline -- and inflammation in the mouth can lead to other inflammatory diseases, such as heart disease, stroke, atherosclerosis, and erectile dysfunction.

It's not normal for your gums to bleed if you are flossing and brushing every day. Bleeding gums despite proper oral care can be indicators for malnutrition, cancer, and other serious conditions.

2. Crooked Teeth
If your teeth are crooked or otherwise misaligned, it's a serious health condition. When teeth aren't properly aligned, food gets impacted in spaces in between the teeth and plaque builds up because these crooked spaces aren't easily reached by a toothbrush and floss. Facilitating the build-up of plaque in this way can lead to gum disease and other inflammatory diseases. Many people think that getting braces or wearing Invisalign are about having a "pretty smile" -- but straightening the teeth is actually a preventative health measure.

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• Strawberries

  Strawberries may help whiten teeth because they contain an enzyme called malic acid, which can be found in some whitening toothpastes, said Louisa Maccan-Graves, celebrity beauty expert and author of "Hollywood Beauty Secrets: Remedies to the Rescue," told AOL Health. You can mash up the strawberry or just rub it on your teeth, cut in half. Leave the juice on your teeth for one minute and then rinse with water, said Maccan-Graves. Dr. Steven Roth, cosmetic and implant dentistry expert, agreed, stating that the fiber in strawberries also behaves as a natural cleaner by removing bacteria from the teeth and mouth. <strong>More From Aol Health.</strong>: <a href="http://www.aolhealth.com/2010/01/29/anti-aging-food/" target="_hplink">Anti-Aging Foods </a> <a href="http://www.aolhealth.com/2010/03/30/improve-your-memory/" target="_hplink">Improve Your Memory</a> <a href="http://www.aolhealth.com/2011/01/07/25-easy-instant-energy-boosters" target="_hplink">25 Easy Instant Energy Boosters</a>

• Apples, Celery And Carrots

  According to Dr. Jeffrey Gross, who teaches in the graduate periodontal program at the Case Western Reserve University School of Dental Medicine, these fruits and veggies act like natural stain removers. The reason: They increase saliva production, which is the body's built-in cleaning agent. "It may sound hard to believe, but some people swear that rubbing raw carrot sticks on your teeth will make them look brighter," said Gross. The added bonus: "These foods are high in vitamin C, which prevents gum disease and gingivitis and kills odor-causing bacteria," Dr. Michael Apa, who specializes in cosmetic dentistry and facial aesthetics in New York City, told AOL Health.

• Citrus Fruit

  Citrus fruit, such as oranges and pineapples, also cause the mouth to produce more saliva, which help clean the teeth and whiten your smile, said Apa. Lemons, in particular, are particularly good for teeth whitening. "Just as they naturally 'bleach' your hair, lemons will lighten and brighten your teeth," Roth told AOL Health. He suggested rinsing with half water, half lemon juice once or twice a week. However, do not rinse with this concoction more than two times a week and do not rinse with straight lemon juice. "Overdoing it would be too acidic, which can be damaging to the teeth."

• Yogurt, Milk And Cheese

  "Dairy products have lactic acid, which decreases gum disease and maintains development and maintenance of teeth," said Apa. "Even the milk in coffee counts -- and it has the added benefit of [decreasing] coffee's staining ability." Along with protecting and strengthening the enamel, hard cheeses, like cheddar, are more effective at cleaning and whitening the teeth than softer cheeses, since hard cheese helps remove other food particles. "And keep in mind that dairy products and foods fortified with calcium and vitamin D are important not only for healthy teeth but your jawbone, the foundation for your teeth," added Apa.

• Baking Soda

  All of the experts agreed that baking soda is one of the strongest -- and safest -- whitening ingredients out there because it's an acid neutralizer that gently removes stains and buildup from the enamel. If this mild abrasive agent is not already mixed into your toothpaste, you can sprinkle a bit on top of your paste each day. Roth also suggested brushing with straight baking soda twice a month. "This is similar to what your dental hygienist does."

• A Straw

  When drinking dark beverages, like soda or grape juice, Roth suggested sipping them through a straw. "The straw allows food dyes to bypass teeth altogether."

• Hydrogen Peroxide

  Gross and Maccan-Graves both stated that rinsing with this antiseptic a couple of times a month can also brighten your smile, thanks to its oxidizing agents. Many mouthwashes are alcohol based, but hydrogen peroxide is an antiseptic. "Mouthwash kills existing bacteria, but hydrogen peroxide prevents the growth of bacteria," said Gross. "You can gargle daily with hydrogen peroxide, but it always needs to be done in a 50/50 solution with water. Hydrogen peroxide is good for preventing infections and can also be helpful for preventing bad breath, which is often caused by bacteria." Mix equal parts hydrogen peroxide with water (about one tablespoon each) and swish around teeth for 60 seconds. "After a minute, spit it out, leaving the bubbling and whitening action of the peroxide [to] sit on teeth for another minute or two, then rinse mouth with water," said Maccan-Graves.

• Brush And Strip

  Apa advised brushing daily with a whitening toothpaste. "Crest Weekly Clean is a good product because it contains heavy silica ingredients that work to brush stains away," he said. Most over-the-counter whitening strips contain a peroxide-based whitening gel to brighten teeth, and Apa recommends Crest 2-Hour Express Whitestrips, which are made with an advanced-seal, no-slip technology that allows you to talk, drink water and go about your day. <strong>More From Aol Health.</strong>: <a href="http://www.aolhealth.com/2010/01/29/anti-aging-food/" target="_hplink">Anti-Aging Foods </a> <a href="http://www.aolhealth.com/2010/03/30/improve-your-memory/" target="_hplink">Improve Your Memory</a> <a href="http://www.aolhealth.com/2011/01/07/25-easy-instant-energy-boosters" target="_hplink">25 Easy Instant Energy Boosters</a>

3. Clicking or Popping Jaw or Earaches
An earache or sharp pain right in front of the ear can be a sign that you are suffering from TMD (Temporomandibular Disorders). Symptoms of TMD should never be ignored because TMD is a progressive disorder, meaning it only gets worse. If you wait to see a dentist, you may reach a point of no return where the only solution is painkillers for the rest of your life.

Causes of TMD include grinding or clenching the teeth, dislocation of the jaw, arthritis of the jaw, and stress.

Common symptoms of TMD:
• Pain or tenderness in the face, jaw, neck and shoulders, or in or around the ear when you chew, talk, or open your mouth wide
• Limited ability to open your mouth wide
• Jaw getting stuck or "locked" while mouth either open or closed
• Clicking or popping sounds in the jaw joint when opening or closing
• A tired feeling in the face
• Difficulty chewing or uncomfortable bite
• Headaches, dizziness, earaches, hearing problems

4. Flat Teeth
Look in the mirror -- do your front teeth look like they're all the same length or appear worn flat at the bottom? This is an indication that you have been grinding your teeth for quite some time.

See your dentist if you suspect you might be a grinder. Years of grinding have led to people wearing their teeth down to the point of needing veneers or crowns. Grinding can also be an indication that you're struggling to keep your airway open at night, meaning you might have sleep apnea.

5. Bad Breath Despite Flossing and Brushing
If you still have bad breath despite flossing daily and brushing at least twice a day, I'd recommend using a tongue scraper. If bad breath persists after that, you may have a more serious underlying condition, including a liver or kidney disorder and diabetes.

6. Increased Tooth Sensitivity to Hot and Cold
After grinding your teeth for many years, the gums recede and small V-shaped indentations form at the base of your teeth. The strong compressive forces of grinding lead to loss of tooth structure in these areas. These defects are called abfractions and they make your teeth overly sensitive to hot and cold food and liquids, or even to breathing in cold air. Sudden onset of tooth sensitivity can be caused by many factors.

7. Tooth Pain
If you have throbbing tooth pain when trying to bite into a bowl of ice cream or other cold food, it could be that the tooth's nerve has become damaged. Get it out checked out at the dentist's office because it could be a cavity, in which case, the bacteria in your mouth could infect the tooth and you don't want the infection to spread to other parts of your body.

8. Snoring
Snoring is another indication that you may have sleep apnea, as it indicates that your airway closes when you approach the deeper stages of sleep. See a sleep specialist MD and see your dentist to have a mandibular advancement device made for you. The mandibular advancement device will keep your airway open at night, stop the snoring, and improve the quality of your sleep, and health, immensely.

9. Flossing Only Before Your Dentist Visit
Does this sound like you? Many people skip flossing until a week or a few days before their dental appointment, in fear of the hygienist's lecture. This is what I like to call a symptom of denial -- no one likes flossing, but it's absolutely critical to the health of your entire body (not just your mouth) and to preventing disease. Get in the habit now if you aren't already -- you'll save yourself decades of pain and big dental bills later on in life.

As you work to get yourself in the habit, remember this: one day of flossing won't impact your health -- just as one day of exercise isn't going to improve your health either. It'll take time to develop the habit so don't be too hard on yourself when you forget.

10. Fearing the Dentist
If you're not having regular dentist visits because you're afraid of the dentist, this could be a symptom of dental anxiety, which should never be ignored. People who suffer from dental anxiety are often told to "buck up," which is the wrong approach and is why it's so important to instil in your children good dental habits and make sure they have a pleasant experience at the dentist. Dental anxiety is a serious condition that prevents millions from getting the care they need each year. If you have dental anxiety, find a dentist who specializes in addressing it. Years of not seeing the dentist only exacerbates the problem, leaving people with huge dental bills decades later, in compromised health, and a lot of pain.

Follow Mark Burhenne on Twitter: www.twitter.com/askthedentist