Teeth whitening doesn't work on dentures, crowns, fillings or veneers. What are the risks of teeth whitening?

The mere mention of teeth whitening can produce fear in man,y though, as they imagine cheap, ineffective treatments that do little more than increase sensitivity. The other side of it is exorbitantly expensive surgical treatments that only the likes of Simon Cowell can afford. Active ingredients: For optimal teeth whitening results at home, "look for the active lightening ingredients hydrogen or carbamide peroxide," advises Sharon Huang, D.D.S., MICOI, a cosmetic dentist and founder of Les Belles NYC in New York City. Note that although hydrogen peroxide produces excellent whitening effects, it can sometimes result in temporary tooth sensitivity, Dr. Gonchar says.Teeth whitening by a dentist or other dental professional can generally only be done privately because it's considered to be a cosmetic treatment. Costs vary and laser whitening is more expensive than professional bleaching. Teeth whitening isn't permanent. It can last from a few months to up to 3 years – it varies from person to person.

Some beauty salons offer teeth whitening, but this is illegal if there's no dental professional present, and it may put your oral health at risk. More and more people are paying for brighter, whiter teeth. But does teeth whitening work and is it safe? Here are the answers to common questions about the treatment. What is teeth whitening?

You may also want to ask them whether there are any risks involved – for example, increasing the sensitivity of your teeth. Genetics, the environment, lifestyle, diet and ageing can all make teeth look yellow and darker. The most common reason for yellow teeth are surface stains on your enamel, which are usually caused by what we eat and drink, or if we smoke. Teeth whitening involves bleaching your teeth to make them lighter. It can't make your teeth brilliant white, but it can lighten the existing colour by several shades. Who can do teeth whitening? You can also buy DIY home teeth whitening kits but these may also carry risks. What happens during teeth whitening?

Leading New York City cosmetic dentist, Dr. Stephanie Dumanian, highly recommends this kit by GLO. “GLO products are top of the line. Their take-home whitening kit provides fast whitening results without being abrasive to your teeth or gum. The advanced technology GLO’s kit offers can help to amplify whitening results received in-office and help maintain those results over time.” Mind you, Dr. Dumanian is the reason behind the popular glimmering smiles of celebs like Busy Philipps and Ashley Park, so you know she'll only suggest the best of the best. Sensitivity-friendly ingredients: If you have sensitive teeth, "carbamide peroxide is less sensitizing than hydrogen peroxide because it takes more time for the whitening action to occur," Dr. Huang explains. For extremely sensitive teeth, there are also products that don’t contain peroxide, and instead are made with ingredients like aloe vera and coconut oil, which have natural whitening effects that pull stains from the teeth, she says. "They're not as effective as peroxide, but are a good natural option that’s gentler on the teeth," Dr. Huang notes. At-home teeth whitening kits are a more accessible alternative to professional whitening treatments, which can deliver instant and more dramatic results but at a higher price. DIY teeth whiteners can include whitening strips, trays, gels, pens, toothpastes, mouthwashes and LED lights as accelerators, which can provide noticeable effects both immediately and with use over time. "They use various chemical or abrasive agents to lighten or remove stains on your teeth to make them appear whiter," explains Marina Gonchar, DMD, orthodontist and owner of Skin to Smile in Morristown, New Jersey. Concerned about the colour of your teeth and considering your whitening options? If your teeth are less than pearly white and you long for a dazzling Hollywood smile, you might have considered purchasing a teeth whitening kit online. But DIY teeth whitening does come with a number of risks so it's always best to opt for a procedure carried out by a dentist.

How we tested

Teeth whitening is a form of dentistry and should only be carried out by a dentist or another regulated dental professional, such as a dental hygienist or dental therapist, on the prescription of a dentist.

The dentist will take an impression of your teeth to make a mouthguard and tell you how to use it with a bleaching gel. Then, using your mouthguard at home, you regularly apply the gel for a specified period of time over a few weeks. Some whitening gels can be left on for up to 8 hours at a time, which can shorten the treatment period. You will then take home your individualised whitening trays, which will allow for up to two weeks of top ups at home. Pre-made tray: This is the poor man’s version of the custom lightening tray – in that the process is the same, but the tray isn’t fitted to the exact shape of your mouth. Provided you can cover the entire surface area of your teeth with your tray, it’s a good compromise. If your teeth are a little crooked, though, you may not get an even result. Whitening toothpastes: These work harder than regular toothpastes to remove stains and plaque. To achieve this, they may contain a mild abrasive or bleaching agent, while others contain activated carbon. You can use them in conjunction with other home kits.Any dentist can whiten teeth as long as they're registered with the General Dental Council. Registered dental therapists and dental hygienists can also carry out teeth whitening on the prescription of a dentist. Teeth naturally become more yellow as the years pass. So, perhaps unsurprisingly, you’ll find teeth whitening kits all over the place. If you’re want to invest in a kit that will give you a naturally white smile at the right price without too many unwanted side effects, read our guide below. If you are not happy with the results, speak to the dental professional who carried out your treatment to ask for advice. There are four main types of at-home teeth whitenining products: whitening strips and trays, LED light devices, pens or gels and toothpastes. "The effectiveness of at-home teeth whitening products can vary from person to person, and what works best for one individual may not yield the same results for another," Dr. Katz notes. Here's a guide to what differentiates each of the options and how they function so you can choose the right form for you, according to the dental experts: