Why are my teeth yellow?
Teeth can be yellow, brown or black due to staining on the outer surface of the teeth. The staining can come from tea, coffee, smoking, or any coloured substance. These “external” staining can be removed by professional scale and clean from the dentist.
With age, the stains will slowly penetrate into the microcracks in enamel (the outer layer of teeth) and into the inner dentine layer, making your teeth look more yellow. By doing teeth whitening/bleaching, the process can be reversed and your teeth will appear white again.
How does whitening/bleaching work?
All effective whitening products boil down to active ingredient: hydrogen peroxide. Hydrogen peroxide molecules are able to penetrate into our teeth and breakdown the stains to make teeth whiter again.
Any other product is either not effective or harmful to our teeth. For example, abrasive pastes can remove external staining, but they also strip layers of our teeth away, and acids like lemon can make teeth look whiter but weaken the enamel at the same time.
What’s the difference between all the different whitening products?
As the active ingredient essentially boils down to hydrogen peroxide, the difference is the concentration and the duration of time it is applied to the teeth surface. The higher the concentration and the longer you apply the bleach to your teeth, the whiter they become. When comparing concentrations, the active ingredient is hydrogen peroxide, but commonly, you will see carbamide peroxide, which more stable and breaks down to ⅓ active hydrogen peroxide (e.g. if you see 18% carbamide peroxide, it is equivalent to 6% hydrogen peroxide).
What are the dangers of hydrogen peroxide?
When used correctly, hydrogen peroxide has been shown to safely bleach/whiten teeth. One side effect is that it can cause your teeth to be temporarily sensitive. The sensitivity usually lasts 24-48 hours.
High concentrations of hydrogen peroxide can burn the surrounding gums and soft tissues. High concentrations of hydrogen peroxide applied to teeth for longer than the intended period of time can also damage the nerves inside the teeth, resulting in severe pain.
What types of whitening products are available?
Minimal effect
Toothpastes/mouthwashes – These products typically contain <1% hydrogen peroxide; some may have up to 3%, but how long do you brush your teeth or rinse your mouth for each day? As toothpastes and mouthwashes get everywhere in your mouth, they inherently cannot contain too much hydrogen peroxide.
Some effect
Whitening strips/pens – These typically contain 3-6% hydrogen peroxide. These are effective to some extent, but due to lower concentrations, the whitening effect is limited.
Anything less than 6% hydrogen peroxide can be bought over the counter. Anything above 6% is required by law to be only sold, supplied and used by dental practitioners due to the dangers of bleach mentioned above.
Effective whitening treatment
Take home bleaching kits – With precise custom made bleaching trays, these are designed to apply an even thickness of bleaching gel on the teeth, while minimising any excess from going onto the gums. Bleaching gel concentration is typically around 6-10% hydrogen peroxide, and is applied to the teeth for 30-60mins a day for 1-2 weeks. Treatment ends when you find your teeth are already as white as they can get, or the sensitivity becomes too painful to continue use.
In-office bleaching – Dentists use 30-35% hydrogen peroxide gel and light/heat activation to accelerate the bleaching process. Treatment time is usually 45 – 60mins. Great care is needed to protect the gums and soft tissue from coming in contact with the bleaching gel.
Is whitening/bleaching effective for everyone?
Although hydrogen peroxide will work on most people’s teeth, it will not work on the following:
- Any type of fillings, veneers, or crowns
- Discoloured teeth from root canal treatment (these need bleach placed inside the teeth, called “internal bleaching”)
- Antibiotic stained teeth
- Discoloured teeth from birth
Conclusion
There is no magic to whitening teeth. You need a high enough concentration and a long enough duration for hydrogen peroxide to be effective. At the same time, hydrogen peroxide is a potent chemical that can be dangerous, so it is very important to adhere strictly to the instructions given.
There will always be sensitivity accompanying an effective bleaching process. The amount of sensitivity will vary between individuals and concentrations of hydrogen peroxide used. If you already have sensitive teeth, then in-office bleaching may not be for you. It is probably better to use a lower concentration take-home bleaching kit. It will take longer to achieve the desired result but with less sensitivity.
At Pinewood Dental Group we provide take home bleaching kits with different concentrations to cater for people with different levels of teeth sensitivity. We have avoided in-office bleaching altogether because we have found the risk of severe sensitivity/pain from in-office bleaching, with no better results than take-home bleaching, outweighs the convenience of in-office bleaching. The cost of in-office bleaching can also be twice as much as take-home bleaching kits.