Changes in the colour of your teeth may happen gradually. Some yellow colour may be inevitable. Teeth can look more yellow especially as you age. As the outer enamel wears away, the yellow dentin underneath becomes more visible.

Bleaching

Bleaching performed by your dentist is really not the best way to whiten your teeth. This is because dentists use products that contain hydrogen peroxide. To protect your teeth, the dentist will protect your gums, tooth enamel, and the rest of your mouth from damage during the procedure, which lasts for about an hour.

Adjust your lifestyle

Tobacco, with its tars and nicotine, is one of the major causes of yellow teeth. Tobacco use, along with consuming certain foods and drinks, such as red wine, dark sodas, coffee, and tea, can stain teeth and cause them to yellow.  
 

 Proper brushing

One of the best ways to prevent teeth from yellowing any more than normal is to take proper care of them. Keep up with brushing and flossing, and use toothpaste that's not too abrasive.
 

Quit grinding teeth

One surprising contributor to yellowing teeth is grinding. If you're a chronic teeth grinder, the extra stress could contribute to ageing and yellowing of the teeth.
 
Lemon, orange, or banana peels

Rubbing lemon, orange, or banana peels on your teeth will make them whiter. It's believed that the compound d-limonene, which is found in some fruit peels, will help to whiten your teeth. Gently rub the fruit peels on your teeth for about two minutes. Make sure to thoroughly rinse out your mouth and brush your teeth afterwards.