One you mix baking soda, hydrogen peroxide toothpaste and water together, would it be a good whitening treatment?

No. Not a good idea to try to be your own chemist. Wrong concentrations can be harmful. Best whitening either in-office or via gels provided by your dentist applied via custom made trays. Short of that try crest white strips. Be sure to follow package instructions exactly.
Surface Stains. The mixture you want to make will remove superficial stains, making your teeth look cleaner, but it will not change the color of your teeth. Baking soda is abrasive, and overuse of h2o2 can cause gingival irritation. If you really want whiter teeth, you will have to purchase whitening gels/strips from your drugstore or for a better result have your dentist use professional products.
No. Hydrogen peroxide should be in contact with your teeth for many minutes, and if you mix everything together yourself, you risk an inexact mixture that could cause harm. Just buy and follow directions for 'crest white strips'!

Related Questions

Will mixing one teaspoon of hydrogen peroxide and baking soda, with a bit of toothpaste and water whiten my teeth? If so, how often can I do it?

Yes. Hydrogen peroxide is the active ingredient to whiten teeth, diluting it with water will decrease potency and results. Too frequent use of peroxide can cause pre-cancerous changes in the gum tissue, especially if there is also use of alcohol or tobacco or a family history of oral cancer. If you limit frequency to a couple of times per week, there is little risk of problems - daily is too frequent. Read more...
Perhaps but... That technique might be helpful in some small way to removed surface stains and is even less effective to internally whiten teeth. Start with a visit to your dentist who can examine you, professionally clean your teeth and if necessary discuss the many more effective ways of achieving whiter teeth and a nicer smile. Read more...
Teeth whitening. Yes, you can mix H2O2 with baking soda and tooth paste. Do it twice a week until you have reached the results you want. However, they are not so effective and/or stable. A professional home whitening system with custom trays for the long term effect is the best. You will be very happy with the results. Read more...
DDS whitening-best. My best suggestion would be to have professional whitening done by your dentist. It is the concentration of the peroxide in the gel form that gets teeth whiter. Over the counter bleaching does not contain the same percentage of peroxide. If you are going to invest the time and money, do it correctly. Read more...
H2O2. Bleaching teeth requires the teeth to be 'bathed' in the bleaching agent, whether it is an adherent strip or a tray that gel is dispensed into, it takes time for the bleaching agent to penetrate the enamel and into the dentin, break down and release hydrogen peroxide into the tooth structure. It can also take several months to achieve a significant result. See your dentist and do it correctly. Read more...
Not Really. It may remove some surface staining, but it will not really whiten your teeth. It it were that easy, there would be no need for whitening gels and professionally applied products, right? Excessive use of peroxide and baking soda can damage your gums and enamel. Have it done professionally. Read more...