Yikes J smoke. I am a dentist and I would not recommend putting an unknown material in your mouth, on teeth and gums. And that % near your teeth or gums carries a high risk. Who knows what the long-term consequences will be of your dental treatment. It causes dental nerve inflammation and it can cause gum damage if it is the genuine material. You cannot purchase the dentist only carbamide peroxide it is not available to the public.
Having your teeth professionally cleaned (scale and polish) helps remove the plaque and hard deposits (calculus) which do stain. Plus the dentist can make sure you have no cavities, all your teeth are sealed (including any root-filled teeth) and you have no active gum disease (periodontitis).
Forget in-office whitening with lasers, bright lights it is nonsense and a waste of money.
If your natural teeth, front teeth, have solid colours and are yellow/orange they will bleach well.
If your natural teeth have a lot of translucency you can't bleach glass! If you have naturally light tooth shades then you will get a subtle result.
Home whitening (£200 to £300)
The 10% home whitening technique is over 100 years old and it has good evidence for safety and effectiveness. The dentist makes impressions and fabricates thin latex gum shields. You apply the gel overnight or 2 hours a day. it takes 4 to 6 weeks. You can extend the treatment period. It is safe. Common complications are transient tooth sensitivity. The results are very good. You tend to reach a plateau where things don't whiten any further. The results are long-lasting. You don't need to repeat it for well over 10 years.
https://optident.co.uk/product/opalescence-pf-10-melon-40-x-1-2ml-syringes/
Maintenance
Professional cleaning is best. The tooth whitening toothpaste is very weak and will not whiten but may help maintain the result. I don't use them personally.
Crest strips
I am told they are very good and I have bought them for friends and gave them away. They liked them. There is a UK dental supplier to dentists. They are about £30 a box wholesale.
The best way is dentist supervised home whitening as outlined above.
And why I have your attention brush your teeth twice at night before bed with a fluoride toothpaste, and on one other occasion through the day. Use a medium head adult brush or an ETBrush. Spit out the toothpaste but don't rinse. Leave the fluoride on your teeth to remineralise them. And you techys should not eat loads of sweets and sugary drinks all day!