Are you worried about your yellow teeth? Worry not as there are more ways to get back your pearly whites. The teeth discoloration reasons are many and occur due to several reasons. Though oral hygiene could be one of the main reasons that affect the appearance of your teeth, yet there are factors like diet, health conditions, genetics, and advancing age that also play a vital role. Sometimes the colour change in the teeth is very subtle as you age. The enamel tends to wear out, and the dentin below becomes visible. Luckily, it is not necessary to visit your dentist or rely on chemicals, as there are easy home remedies for whitening the yellow teeth that will have them all sparkly and bright in no time!
Reasons for Yellow Teeth:
A. Smoking:
Several factors can cause discoloured teeth, and nicotine is one reason where teeth can get discoloured over time. Smoking makes your teeth yellow. Smoking can result in the enamel of the teeth to stain. Once you begin smoking, it does not take long before your teeth have a yellowish appearance to it.(1)
B. Coffee/Tea:
There is nothing like starting a day with coffee or tea, but not many are aware of what it does to your teeth. Coffee/Tea leaves a stain on your teeth because it contains an ingredient called tannins.(2) It is a type of polyphenol that is found in wine and tea too. Tannins tend to stick to your teeth and leave a yellow stain behind.
C. Excess Sugar:
Sugar is one of the reasons for yellow teeth making sweets one of the main culprits. Sweets damage and stain teeth. Sugar residue on teeth invites bacteria and becomes food for it in our mouth. These end in the darkening or yellowing of teeth. They also end up causing cavities in our teeth.
D. Vitamin Deficiency:
Periodontitis is a condition where there is inflammation of the tissue around the teeth, and this often results in shrinkage of gums and loosening of teeth. Vitamin C deficiency may end up worsening periodontitis, where there is a buildup of bacteria on the gums and teeth. This buildup leads to discolouration of teeth. It is believed that topping up on vitamin C can reduce discolouration, but more research is needed on this.(3)
E. Ageing:
The darkening of teeth due to age is a natural effect of old age and ageing. As we age or get older, the outer covering of the teeth called enamel gets worn out. Ageing teeth discolouration exposes the darker surface beneath it called the dentin. This leads to the teeth looking more yellow or grey than white.(4)
F. Genetics:
Apart from ageing, genetics also play a part in having discoloured teeth. There are two inherited disorders that cause dentinogenesis imperfect and amelogenesis imperfecta. They cause the teeth to develop improperly and could also lead to discolouration. There are instances where one may simply be born with yellow teeth compared to others who have white teeth.
G. Diseases:
Certain disease conditions lead to yellowed teeth. Patients who undergo chemotherapy for neck/head cancers may have stained or yellow discoloured teeth. Bulimia Nervosa also causes teeth to change in appearance and look yellow. There are certain inherited diseases that also cause yellow or discoloured teeth.
H. Medicines:
Some medications that cause yellow teeth are those that are prescribed for blood pressure and asthma. Tetracycline and doxycycline are two antibiotics known to discolour teeth, especially when administered to children with developing teeth, before the age of 8. Certain mouth rinses and washes that contain chlorhexidine and cetylpyridinium chloride can stain teeth too.(5)
Read: Homeopathic Toothpaste for Teeth Whitening
Natural Home Remedies to Clean Yellow Stains on Teeth:
The below-mentioned list has some natural ways to help you brighten your teeth. Check them out and choose the one that suits you the best.
1. Baking Soda And Lemon for Teeth Whitening:
A combination of baking soda with lemon juice is useful for your teeth. Baking soda boosts oral health by balancing the pH level of the oral cavity. The natural bleaching properties of lemon help in achieving white teeth and in the removal of the yellowness. You can either gargle the mouth with lemon juice diluted in water or else rub the teeth with lemon peel. This should be done 2-3 times a day. Lemon juice is one of the most effective home remedies to whiten yellow teeth.
Required Ingredients:
- Baking soda.
- Lemon juice.
Preparation:
- Take a bowl.
- Mix the required quantity of baking soda with lemon juice.
- The paste should be thick inconsistency.
How To Use:
- Take a little of this on your toothbrush and gently scrub the stains on the teeth.
- Let the paste remain for a minute and rinse.
How It Is Helpful:
- This common household product known to all is an effective stain remover, and does a good job on your enamel too! It makes the teeth shiny and is a wonderful plaque and tartar remover. Baking soda and lemon are one of the popular treatments used to whiten teeth.
Tips And Precautions:
- It must be used cautiously and should not be left to remain on the teeth for more than 2 minutes. Use this only a few times in a week and not daily.
Read: Best Teeth Whitening Strips
2. Fruit Peels:
It is claimed by some people that rubbing a banana peel on teeth, lemon, or orange peels on your teeth will make them whiter. Banana is rich in mineral content, and these include minerals such as iron and manganese, which in turn help in regaining the whiteness. One can rub teeth with the inside of the banana or orange peel. Fruit peel help to reduce the yellow tinge. This is the best home remedies for yellow teeth.
Ingredients:
- Fruit peels (banana or orange or lemon peels).
Preparation:
- Take either banana or orange.
- Remove the peel from the fruit.
How To Use:
- Rub the peels against the teeth.
- Rinse well.
How It Is Helpful:
- Lemon has natural bleaching agents, and it is believed that the compound d-limonene, citric acid, which is found in citrus fruits’ peels, helps to whiten the teeth.
Tips And Precautions:
- The fruit’s acidic nature can sometimes erode and wear away the enamel. The minute one notices teeth becoming more sensitive, then this remedy should be stopped.
Read: Best Whitening Toothpastes
3. Oil Pulling:
Oil pulling is a traditional remedy. Since certain modern treatments have side effects, there are still people who believe in this and use the oil pulling method. Oil pulling is beneficial in maintaining oral hygiene and health.
Ingredients:
- Oil pulling may be done with coconut oil or any edible oil of your choice.
How To Prepare and Use:
- Swish coconut oil around the mouth.
- The oil will become thin and milky white.
- Spit out and wash mouth thoroughly with warm water.
How It Is Helpful:
- The lauric acid in coconut oil works against harmful bacteria that can cause bad breath, tooth decay, and gum disease. It leaves the teeth surface clean and white.
Tips and Precautions:
- This should be done early in the morning before breakfast on an empty stomach for about 20 minutes(6) Avoid eating anything for half an hour after spitting out the oil and do this daily to keep dental problems at bay.
- Always use virgin coconut oil for teeth whitening.
4. Seeds and Nuts:
Seeds and nuts are another popular home remedy for yellow teeth. These are structurally working on stained teeth and whiten them in a natural way. Almonds, cashews, sunflower seeds, and walnuts have an abrasive nature when eaten and help to work like exfoliants on our teeth.
Required Ingredients:
- Walnuts/almonds/cashews/sunflower seeds.
Preparation:
- Just take the nuts of your choice.
- Crush and make them into a coarse powder.
How To Use:
- Gently scrubbing of the teeth with crushed powder will exfoliate the teeth well. This will keeps the bacteria under check in the mouth.
How It Is Helpful:
- Nuts are natural cleansers. They can strip away the stains from our enamels and whiten the surface of teeth.
Tips And Precautions:
- Excess rubbing should be avoided as it can erode the enamel of the teeth.
See Also: Home Treatment For Gingivitis
5. Turmeric and Coconut Oil:
Make use of this DIY remedy to remove stains and whiten your teeth. Turmeric and coconut oil is one of the age-old and Indian home remedies to treat yellow teeth with its antiseptic and whitening properties.
Required Ingredients:
- Organic coconut oil – 1 teaspoon.
- Turmeric powder- 2 pinches.
- Baking soda– 1/2 teaspoon.
How To Prepare:
- Combine all the three ingredients to form a paste.
How To Use:
- Use a toothbrush to brush a small quantity of paste on the teeth for a minute.
- Let it remain for 2 minutes and rinse with cold water.
How It Is Helpful:
- Coconut oil contains antioxidants along with a high concentration of lauric acid, this helps to kill the bacteria on teeth.
- Turmeric helps reduce sensitivity and inflammation in the gums.
- Baking soda helps in the removal of plaque, as well as discolourations.
Tips And Precautions:
- Use this remedy only once a week and discontinue it once the teeth are whitened.
- Avoid overusing this remedy.
6. Salt:
Salt is one of the best remedies for whitening the yellow teeth. The most popular one is that which involves a paste made with salt and mustard oil/baking soda. Mix a small amount of salt in the toothpaste each day before brushing to get the desired whiteness on the yellow-coloured teeth. It replenishes the mineral content to the teeth that might be one of the causes of yellow teeth. Salt can also help in reducing the odour-causing bacteria in your mouth and freshens your breath.
Required Ingredients:
- Salt.
- Mustard oil(OR) salt.
- Baking soda.
How To Prepare:
- Choose the combination of your choice.
- Mix salt and mustard oil and put this on a neem twig.
How To Use:
- Rub the twig on the teeth to remove plaque.
How It Is Helpful:
- This helps to replenish mineral content to the teeth and helps it to regain its whiteness.
- You can use salt and lemon also for teeth whitening.
Tip And Precautions:
- Common salt can also be used along with baking soda as a regular tooth powder instead of toothpaste.
- Ensure that you do not rub it roughly on the teeth so that the enamel or gums do not get damaged.
7. Dairy Products:
The lactic acid in dairy products like cheese, milk, and yogurt protects the teeth against tooth decay and whiten teeth. This makes it a yummy remedy and one of the natural ways to whiten teeth. This makes it one of the easy teeth whitening home remedies.
Required Ingredients:
- Cheese/yogurt/milk.
How To Use:
- One must consume at least a small piece of any cheese after every meal as a home remedy for yellow teeth.
How It Is Helpful:
- Milk products are known to keep away the acid and alkaline from the mouth.
- Milk, cheese, and yogurt are good cleaners for yellow teeth and helps to keep away the bad bacteria from the mouth. This is because the cheese increases the pH level of the body and brings down the acid deposited after a meal.
- Dairy products prevent erosion of enamel and discolouration of teeth.
- The chewing of cheese helps to salivate, and this washes away particles that stain the teeth.
Tips And Precautions:
- Dairy products must be taken in moderation, as too much of anything can make even a good product bad.
8. Strawberries:
Strawberries are one of the popular home remedies for yellow teeth to whiten it. And, strawberries are the natural teeth whiteners. Rubbing strawberries on teeth help to remove the stain-causing particles from the teeth, and they are a natural astringent.
Required Ingredients:
- Strawberries.
Preparation:
- Mash a few strawberries.
How To Use:
- Use a toothbrush to brush the above mixture onto the teeth.
How It Is Helpful:
- The malic acid and vitamin C found in strawberries help in teeth whitening.
- The malic acid acts as an astringent that helps to remove surface stains, and vitamin C helps to wash away the plaque making.
9. Hydrogen Peroxide for Teeth Whitening:
Hydrogen peroxide is a useful remedy because peroxide has the ability to penetrate the layers of teeth and remove compounds that cause discolouration. The combination of water, hydrogen peroxide, and baking soda is an awesome home remedy for yellow teeth.
Required Ingredients:
- Hydrogen peroxide.
- Baking soda.
- Water.
How To Prepare:
- Prepare a paste with one tablespoon of hydrogen peroxide and two tablespoons of baking soda.
- Mix this with your toothpaste and brush.
How To Use:
- Scrub your teeth with this mixture for two minutes, and you can see how easy it is removing teeth stains with hydrogen peroxide.
How It Is Helpful:
- Baking soda being abrasive in nature will help to brush away the stains, whereas the hydrogen peroxide will make them lighter with its bleaching properties.
Tips And Precautions:
- Ensure that you do not overdo as being abrasive, it can damage the enamel.
- Tooth sensitivity is one of the most known side effects of hydrogen peroxide usage.
- However, you must make sure that there is no irritation due to the hydrogen peroxide.
- Although it is one of the homemade remedies for whitening teeth fast, caution must be exercised.
10. Neem:
One can make use of neem twigs like a toothbrush to clean your teeth in the morning. It prevents the teeth from turning yellow. Neem is the best herbal remedies easily available at home.
Ingredients:
- Neem twig.
How To Use:
- One can chew on neem leaves or twigs to prevent the teeth from turning yellow.
- Chew on one end of a neem stick until bristles are created at the end of the stick.
- Now rub the bristles on your teeth as you use a toothbrush and show how beneficial is neem for teeth whitening.
How It Is Helpful:
- Neem has antibacterial properties. Neem has been found to be useful against gingivitis(7).
Tips And Precautions:
- It is considered unsafe to use neem oil or neem bark during pregnancy.
11. Onions:
The benefit of eating raw onions works well for teeth whitening and removing stains. This is an anti-plaque vegetable that can work wonders on your teeth. It is also one of the easiest home remedies for yellow teeth.
Ingredients:
- Raw onions.
How To Use:
- Eat raw onions in salads or as part of garnishing for other recipes.
How It Is Helpful:
- The sulfur compounds found in raw onions do not allow plaque to be formed.
Tips And Precautions:
- Avoid eating fried onions or sauteed as it will not help.
12. Cloves:
Clove oil and fluoride make good miracle workers when it comes to dental hygiene. These two play an essential role in caring for teeth and gums. Cloves help to get rid of cavities, as well as strengthen and protect from harmful bacteria. They significantly contribute to all-around oral care. Many are aware that cloves are used as a painkiller, and they are natural teeth whiteners too.
Ingredients:
- Clove essential oil.
How To Use:
- To use clove oil for teeth, use a drop of Clove essential oil on top of toothpaste.
- When you brush teeth with this, there is a slight tingling sensation, but it leaves the teeth looking whiter.
How It Is Helpful:
- This essential clove oil has medicinal properties.
- It is antibacterial and aims at natural dental care.
- It works by removing yellow stains while at the same time creates a whiter appearance.
Tips And Precautions:
- Ensure that you use pharmaceutical-grade clove oil. It is non-toxic and safe.
13. Charcoal:
Activated charcoal may be used to remove stains from the teeth. It is one of the biggest trends today to use charcoal. The crystal-based chemical in charcoal makes it perfect for teeth whitening and in the treatment of yellowness. It is an age-old remedy, which is known for its absorption properties.
Ingredients:
- Activated charcoal toothpaste or mouthwash.
How To Prepare:
- The charcoal powder can be mixed with the regular toothpaste each day for desirable and immediate results.
- This is one of the useful home remedies for cleaning teeth to make teeth white and shiny.
- Apart from the toothpaste, you can make a mouth wash by diluting it with water.
How To Use:
- Use small circles and brush your teeth for 2 minutes.
- Take care to be careful in the area around the gums as it can cause abrasions on the teeth, spit it out.
- If your tooth is sensitive or you want to limit the abrasiveness of the charcoal, you can dab it on your teeth. Leave it on for 2 minutes.
- In case of using a mouthwash, swish it in the mouth for two minutes before spitting it out.
How It Is Helpful:
- It is believed that charcoal can remove stains and pigments from the teeth because it is absorbent, and it also gets rid of bacteria and toxins in the mouth.
Tips And Precautions:
- Do not brush too aggressively.
- Exercise caution while using charcoal, especially because of the lack of evidence to prove its effectiveness and safety. Research has shown that it can be abrasive and can affect tooth structure. (8)
See Also: Natural Ways To Treat Bleeding Gums
14. Apple Cider Vinegar:
Apple cider vinegar is acidic in nature, helps to break down accumulated plaque on teeth, and helps with teeth whitening. It is one of the fastest teeth whitening remedies. It has certain properties, which cleanses teeth well and one of the popular home remedies to get rid of yellow teeth.
Ingredients:
- Apple cider vinegar,
- water
How To Prepare:
- Make a dilute solution of water and apple cider vinegar.
How To Use:
- Rub a bit of apple cider vinegar onto teeth directly.
- While brushing teeth with apple cider vinegar not be too hard while doing so, as it can wear out your enamel and will end up doing more damage than good.
- Brush gently after this using regular toothpaste. Else you can swish dilute solution around the mouth to make use of its bleaching properties.
How It Is Helpful:
- Teeth whitening with apple cider vinegar works well as it is a natural antibiotic.
- It helps to control bad bacteria growth.
Tips And Precautions:
- Avoid using apple cider vinegar daily as it can erode enamel.
15. Limit the Sugar Diet:
Sugar, by itself, does not cause discolouration or yellow-coloured teeth. The sugar residue left behind on the teeth is feasted upon by bacteria. It eats the enamel too, and this leads to the discoloured look when the yellow dentin beneath is exposed. Adopting proper brushing techniques and flossing helps to avoid yellow teeth. Brushing and flossing religiously will help avoid stains on the teeth. Oral hygiene will go a long way in keeping teeth looking healthy, clean, and white. Excess sugar consumption could be causing children’s teeth to turn yellow, so one must be careful about how much sugar the children consume. While flossing, ensure that you do it the right way, as it can damage the gums.
16. Brushing and Flossing:
There is no alternate solution to brushing and flossing. The first plan of action should be to brush the teeth in the correct manner. It is very important that the teeth be brushed after consuming food and drink, as this can lead to yellow teeth. Do not skip flossing as it helps to loosen particles missed by the toothbrush. Improper brushing and flossing could be causes yellow teeth in adults. Brush teeth at least two times a day and for 2 minutes at a time. Make sure that you reach into all the crevices. Use a circular motion to brush your teeth and protect your gums. Sometimes yellowing of teeth is due to brushing or flossing the wrong way, so ensure that the right technique is followed.
17. Use Straw while Cold or Hot Drinks:
Use of staw may help keep stains away. When one drinks juice, or iced coffee or tea, at least the front part of the teeth will be spared from staining. Drinking dark-coloured soda could also be one of the reasons for the causes of yellow teeth. Keep straws handy with you. There are stainless steel straws available, which are not only reusable but also do not create environmental issues with the waste in the form of plastic straws. Try to use a straw whenever and wherever possible while consuming hot or cold drinks. This simple method prevents enamel from being deteriorating and prevents cavities in the tooth. Ensure that you dispose the straws carefully and go in for straws that can be reused.
18. Cauliflower:
Cauliflower and broccoli are coarse vegetables that have whitening benefits, especially when you eat them raw. These are the excellent natural stain remover for teeth. The rough texture of the vegetables that creates a scrubbing action when chewed helps in the removal of stains on teeth.
Required Ingredients:
For the salad:
- Two cups grated cauliflower
- One cup boiled mung beans
- One red bell pepper, diced
- Quarter cup crumbled walnut
- Half a cup green onions, chopped
- Half a cup parsley, chopped
For the dressing:
- Half a cup lemon juice
- Two tablespoons vinegar
- Three tablespoon pomegranate molasses
- One teaspoon dried mint
- One and a half teaspoons salt
How To Prepare:
- Take a bowl and combine all the salad ingredients together.
- In another bowl mix and combine all the ingredients for the dressing.
- Pour this all over the salad and stir well.
How To Use:
- When these veggies are eaten raw, it is difficult to chew, and while
How It Is Helpful:
- Chewing these veggies, it strips the stains found superficially on the surface of the teeth.
- The longer you chew these vegetables, the more saliva is secreted, and this helps to work against stains and make the teeth white.
Tips And Precautions:
- Raw cauliflower is better for overall health than boiling them in water florets and being a versatile vegetable can be easily added to our diet.
19. Pineapple:
Pineapple is the one among natural teeth whitening remedies, which contains bromelain, which is an enzyme that disrupts proteins on the surface of enamel, aids in the removal of stains and discolouration. It is proven to be a natural stain remover.
Ingredients:
- Pineapple 2 cups
- Milk 1-1/4 cups (Badam milk)
- 4 almonds (chopped)
- A pinch of elaichi or pepper is optional
How To Prepare:
- Peel the pineapple and chop into cubes
- Add the pieces to the blender along with the milk
- Now blend well and serve immediately.
- To make badam milk, soak a handful of almonds for 3-4 hours, peel the skin and run through a blender.
- Now add everything to make a delicious smoothie.
How To Use:
- Pineapple used in smoothies, recipes and fruit salads too.
How It Is Helpful:
- When the proteins are disrupted by bromelain, the saliva washes the stains away naturally. This makes the teeth shinier than before
Tips And Precautions:
- Pineapples are sweet by nature; there is no need to add any sugar.
20. Celery:
Your teeth get a great workout with celery and chewing celery not only cleans teeth but also creates enough saliva to neutralize bacteria. Chewing celery also washes away food debris and strengthens gums. This makes celery useful and one of the natural ways to get whiter teeth.
Ingredients:
For the salad:
- Chopped celery (one bunch)
For the dressing:
- Two tablespoons canola oil
- One tablespoon cider vinegar
- Half a teaspoon white sugar
- Quarter teaspoon salt
How To Prepare:
- Place the chopped celery in a bowl.
- Combine vinegar, oil, sugar, and salt
- Shake well in a jar with lid
- Pour this all over the chopped celery
- Your tasty salad is ready.
How To Use:
- Chewing this gives teeth a good workout and massages gums.
How Is It Helpful:
- This is also a natural home remedy that removes yellowness in teeth and keeps away bad breath and gingivitis. They scrub teeth clean.
Tips And Precautions:
- Celery is a versatile veggie that can be eaten cooked as well as raw.
21. Healthy Food for Teeth:
Listed below is some of the most beneficial food for teeth,
- Cheese counteracts the acid left behind after a meal. It protects teeth from acid erosion.
- Fatty fish like salmon is a vital source of vitamin D. It allows your teeth and gums to get the full benefit of calcium from the food you eat, and vitamin D is vital to allow your body to absorb calcium.
- Oranges contain vitamin C, and this strengthens blood vessels and connective tissue. It slows down the progression of gum disease by reducing inflammation.
- Green and black tea suppress the presence of acid-producing bacteria in the mouth that otherwise would stain teeth.
- Fruits and vegetables are good for teeth where veggies like carrot, celery, cauliflower, broccoli help in washing away stains from the teeth along with kiwi, strawberries, etc.
- Include in your diet some calcium-rich food for your bones and teeth like milk, sardines, soy milk, figs, yogurt, cheese, and green leafy vegetables.
- Chewing gum for healthy teeth is popular nowadays, where calcium is being added to chewing gums to promote enamel remineralization.
- Spinach is rich in magnesium and potassium. It is effective in strengthening teeth and bones.
- Papaya is another fruit that has an enzyme called papain similar to bromelain that helps best to remove stains on teeth.
22. Foods to Avoid or Reduce for Healthy Teeth:
Some foods to avoid are:
- Tea and coffee contain tannins, one of the main reasons that cause teeth to turn yellow. It is believed increasing the milk in tea or coffee may assist in counteracting staining.
- Cola with dark coloring tends to be another reason for yellow teeth
- Dark-colored fruit juices, such as blueberry, cranberry, and grape juices, leave stains on teeth and one of the common teeth discoloration reasons.
- Tomato-based sauces have a pigment that tends to stain teeth.
- Several curries sometimes leave telltale signs on teeth and are common causes of foods that cause yellow teeth.
- Balsamic vinegar has a deep pigmentation, which sometimes may stain teeth.
- Soy sauce has a dark colouring, which may tend to stain your teeth.
- Berries such as blackberries, blueberries and cherries can stain teeth.
- Beetroot is another veggie packed with vitamins but can leave a stain on your teeth.
One does not have to go through life with stained yellow teeth, especially when there are easy natural ways to get whiter teeth in the form of home remedies. There are natural teeth cleaning remedies that are available to remove and keep the stains away, brightens, and whitens teeth. It is aptly said that a smile is worth a thousand words, so get ready to flaunt your pearly whites with the countless remedies available to recover the whiteness of your teeth back!
Frequently Asked Questions and Answers:
1. What Are Whitening Strips?
Whitening strips are shaped to fit the teeth and have a thin layer of peroxide gel on strips. The strips help to lighten teeth by two shades. These products are available online, and you can find that there are instructions given on their usage accordingly. Some of the strips should be applied two times a day, for 30 minutes. Most of these strips are safe to use for yellowish discoloration of teeth. Exercise caution while using strips with chlorine dioxide, as it can damage the enamel.
2. Is It Expensive To Get A Teeth Whitening Treatment?
Yes! Teeth whitening treatments done by experienced doctors can cost a fortune. Laser teeth whitening treatments are very expensive and are the fastest whitening procedure available. These dental procedures are not covered by dental insurance programs. Today, more people are opting for home remedies as ways to whiten teeth at home, not only to save time and effort, but they are also safer compared to chemicals used. In severe cases of teeth staining, we may have to opt for professional help where it may require one or two sittings.
3. What Are The Benefits Of Fluoride toothpaste?
Fluoride is a natural mineral, and fluoride toothpaste helps to build strong teeth. It prevents cavities and combats bacteria that are harmful to teeth and gums. Fluoride is very useful and helpful in removing stains and preventing decay. It is very beneficial for those who are at high risk of developing cavities or dental caries. There are special fluoride rinses and gels that can be used for whitening the yellow teeth at home. Though fluoride cannot remove decay, it can prevent teeth from getting decayed and create a strong outer surface to our teeth.
