First of all you need to buy baking powder[and no we are not baking a cake]!baking powder usually costs about 3 pounds 50.before you brush your teeth wet your toothbrush a little and sprinkle baking powder over it.start brushing your teeth like you regularly do.after a couple of days of doing this routine you will start to notice a change in your teeth!it gets whiter and whiter!I tried this and it really worked!
Eat raw fruits and veggies
Eating fruits, vegetables, and other crunchy foods is good for your body and your teeth. Eating nuts, raw carrots, apples, and cauliflower can help keep your teeth clean by removing surface stains and plaque that leads to cavities.
I don't recommend using baking soda on your teeth especially if you have sensitive teeth / gums. It can erode tooth enamel. I think the best way to whiten teeth is to gently and thoroughly brush teeth for at least a couple of minutes with a soft bristled brush. A lot of people brush too hard which damages teeth. Make sure to clean the back ( wisdom teeth ) because food particles get stuck there can lead to tooth decay. Apply a flouride / whitening toothpaste ( i like Tom's of Maine Simply White ) on your teeth ( with a brush ) and leave it on for 30 minutes before brushing. It helps strengthen tooth enamel and remove stains. The flouride in toothpaste really works and keeps dentin strong, just don't swallow.
You shouldn't use whitening products ( crest strips, baking soda, etc. ) everyday and never longer than the recommended time. I use 3% hydrogen peroxide ( sold in brown bottles ) and toothpaste to whiten my teeth and it works great. Just dip a cotton swab in peroxide and rub it on your teeth. Leave it on for five minutes or shorter depending on how sensitive your teeth are and brush.
Also, check your diet. Eliminate cariogenic foods like sugar and processed foods and don't eat too much fruit ( i only eat fruit once in a while and focus more on green vegetables like broccoli ). It's also a good idea to take a quality (natural not synthetic) magnesium and vitamin d supplement (i take Bluebonnets Chelated magnesium and Nordic Naturals d3). Do not take a calcium supplement because it can cause kidney damage. Our bones need more magnesium and vitamin d than calcium. You can get plenty of calcium from eating vegetables and beans like steamed collard greens.