Is it true when you have your teeth whitened they only do 16 8 at the top and 8 at the bottom?

Although I understand your logic, check retractors are not the best alternate. There are two reasons why this is happening. Either your trays are not made correctly because gel should not be able to seep through the top of the trays OR you are over filling the trays. 

My suggestions are as follows:check what % gel you have first and foremost. Most people can easily tolerate the normal concentrations. But there are some stronger ones that some people just cannot use.only use a pea size amount of fell in each teeth space.***always wipe gently with a Kleenex in...

Your dark tooth due to root canal, can definitely be covered if your dentist uses a porcelain fused to metal bridge, either precious metal or gold.However if you do want to have a non metal bridge, it is best to use lava, with an opaque core, however I have seen even with a lava bridge, some...

It sounds like you have reached a plateau. Your teeth have a whitening range of how white your teeth will bleach. If you are not happy with the results at home, you may want to try an in-office session at a dental office with stronger bleach. 

Teeth whitening is a popular treatment for many, due to the unrivaled improvements it can give the appearance of our teeth. I would say that 16 is about the minimum age before one should even consider teeth bleaching, but most young people have not had the aging and staining effects to their...

Unfortunately dental bonding is not affected by teeth whitening. The existing dental bonding will need to be replaced to match the lighter color of your teeth following teeth whitening.