@Ariel
As per my experience with my patients,I am describing your the following

The color or your teeth may have nothing to do with cavities. Teeth are porous, like a sponge. You can discolor your teeth from food or beverages like beets, blueberries, mustard, soya sauce, red wine etc. If the pigment from these foods goes deep inside the enamel and into the dentin, you will have to whiten your teeth probably using some sort of peroxide. However, you can still get cavities even with white teeth. It is a function of bacteria in plaque giving off acids that dissolve enamel. Now, if you have not cleaned your teeth for weeks and the plaque buildup makes your teeth appear yellow, that is another matter.

@GeorgeAReinhold Ever looked in the mirror and wondered how your teeth got so yellow? Many of us have. Because yellowing can happen gradually, it can easily go overlooked. Luckily, yellow teeth are not a sign of a serious medical condition
Ever looked in the mirror and wondered how your teeth got so yellow? Many of us have. Because yellowing can happen gradually, it can easily go overlooked. Luckily, yellow teeth are not a sign of a serious medical condition. And while it may be disheartening and confidence-shattering to feel like you’ve lost your best accessory—your bright, white smile—you can get it back. For starters, be aware of what causes yellowing, and how you can avoid or limit exposure to those things.

What Causes Yellow Teeth?
REASON #1 You’re Getting Older
Your teeth can also start yellowing as a natural part of the aging process. This happens as the strong, white protective coating on teeth, known as enamel, fades over time because of everyday wear and tear on your teeth.

REASON #2 You’re a Smoker
Tobacco products, from cigarettes and pipe smoke, stain teeth. If you consume these products, your teeth will darken over time.

REASON #3 Your Oral Hygiene Is Lacking
When you do not routinely brush, floss and rinse your mouth to remove plaque build-up and tartar, this can hasten the discoloration of your teeth.

REASON #4 You’re on Medication
Certain medications, such as the antibiotics doxycycline and tetracycline, can darken the teeth of children younger than 8 years old. Some antihistamines, drugs for high blood pressure and antipsychotic medications can also stain adult teeth. Go over any such potential side effects of the medications you are currently, or may start taking, with your physician.

REASON #5 You Have an Illness
A less common cause of tooth discoloration can be either a disease that affects enamel, or the treatment of a disease, such as chemotherapy and/or radiation used to treat cancer. In this case, the discoloration is more of a brownish color.

REASON #6 The Yellow Is in Your Genes
It also may be possible that you inherited enamel that is more yellow than that of other people whose genes differ. If you notice your teeth are more yellow than you’d like, you can fix the issue by using any number of whitening strips, toothpastes and LISTERINE mouthwashes to restore your bright smile.

How to Whiten Yellow Teeth?
Yellow or faded teeth are an issue that a lot of people struggle with. At times, teeth become yellow and stained due to bad lifestyle choices such as smoking, alcohol consumption, and excessive caffeine intake. Other times, tinted teeth can a sign of poor dental hygiene. Dental issues can also cause discolouration in the teeth.

Read our guide on teeth whitening and home remedies & other tips you can make use on whitening yellow teeth

What is the correct time for brushing teeth and exact quantity of toothpaste to be used for stomach and dental health.
I need detailed information about my dental care.
Please guide