The top three reasons of teeth yellowing are:

1. food/drinks : colas, teas and wines

2. Tobacco use

3. Poor dental hygiene : causes a build up of plaque

APPLES ~ Apples are nature's toothbrush. As you chew, you are removing excess food and bacteria. Apples have malic acid, which is found in teeth whitening products, that help dissolve stains.

RAISINS ~ Raisins are a natural mouthwash that keep teeth clean by inducing saliva. Saliva helps wipe away plaque. 

FLOSSING ~ Flossing your teeth will make them appear whiter because you remove the plaque between your teeth. Plaque causes your teeth to appear yellow.

CHEESE ~ Eating a small amount of cheese after a meal can help prevent tooth decay and promote enamel re-mineralization. Cheese contains mineral calcium and phosphorus which helps make the enamel stronger. 

SUGAR-FREE GUM with XYOLTOL ~ Plaque feeds on regular sugar but can't digest xyoltol so chewing it will prevent plaque. 

* At Home Remedy

Mix baking soda and the juice of a lemon. It should bubble a bit. Clean and dry your teeth with a cotton swab. Apply the baking soda mixture to teeth and leave on for ONE MINUTE. Gentle brush.

Avoid using toothpaste with baking soda. While baking soda is great for removing plaque and stains, using it long term can actually damage the enamel of your teeth.