Two major points to consider; 1. Safety 2. Effectiveness
Safety – As already mentioned illegal tooth whitening is still rife and combinations of ill fitting, leaking whitening trays and formulations containing dangerous acids and abrasive particles pose a serious risk.
The legal limit of Hydrogen Peroxide (the agent used for tooth whitening) that dentists can prescribe in the UK is 6%. Regulations in the UK limit the amount of Hydrogen Peroxide to maximum 0.1% for any off the shelf system. This is 6000 times weaker than the professional whitening and has very little to no impact on improving the long term whiteness of the teeth. Beware of the “whitening toothpastes” many of these are abrasive and may remove some surface stains but will also rub away enamel over time.
Effectiveness – A lot of social media influencers who pose on the Internet using various whitening strips, paint and UV lights. Unfortunately the reality of these systems are that all they do is dehydrate the teeth so that very temporarily (48 hours maximum) they will look slightly whiter. There is a big question mark over many of their safety and long term damage to the teeth and gums.