Teeth whitening: the brightest smile

Teeth whitening the lowdown
Reading Time: 11 minutes

Are your teeth looking a bit yellowish? Well, you don’t have to live with it. Dental hygienist and tooth whitening expert, Sarie Liebenberg, tells us all we need to know about teeth whitening.

How does teeth whitening work?

A tooth with its semipermeable membrane, will allow whitening agents such as peroxide to penetrate the dentinal tubules within 15 minutes. Whitening products contain an active ingredient of either hydrogen peroxide or carbamide peroxide. Hydrogen peroxide breaks down into water and peroxide radicals (oxygen ions), also known as whitening molecules, as it is absorbed into the tooth. 

These radicals have unstable electrons that seek to bond to unsaturated double bonds, which usually have a yellow pigment. Free radicals react with the double carbon bonds that hold chromophores in stain molecules, breaking them down into single carbon bonds. While double carbon bonds are responsible for the yellow colour in stains because they absorb light, single carbon bonds reflect light, making the teeth appear whiter and brighter as the stain molecules become vaporised.

Is teeth whitening harmful to the teeth?

No, teeth whitening does not damage the tooth layers or integrity of the tooth.

Why do some people have yellow teeth?

Just like the colour of your skin and eyes, we are born with a certain tooth colour that we genetically inherit from our parents. Baby Yum Yum - How does teeth whitening work

The outer layer of the tooth above the gum line is called the enamel and underneath it is a thick layer called dentine. Dentine also extends underneath the gum around the roots of the tooth. Dentine makes up the bulk of the tooth and is dense in structure. The dentine is darker than the enamel, whereas enamel is semi-translucent. 

The colour of your teeth is determined by the colour of the dentine, not the enamel. The dentine will shine through the enamel. So, the darker the dentine, the darker the tooth appears. To change the colour of your teeth, we need to change the colour of the dentine. There is a misconception that teeth whitening changes the colour of the enamel–teeth whitening will penetrate the enamel but the change in colour will occur in the dentine.

Why do teeth become darker as we get older?

Extrinsic staining results in surface stains on the enamel and this happens through our diet and lack of good hygiene. A person with a diet high in chemical compounds, called chromogens (eg. Tea, coffee, red wine, nicotine) will usually have stained teeth if dental plaque is not removed properly. When a person does not practise good oral hygiene, the bacterial plaque left on the teeth will create an ideal uneven and rough surface for stains to adhere to. If you drink moderate amounts of tea, coffee and red wine, and you practice good oral hygiene, you’re less likely to have stained teeth. It is very hard for staining to adhere to a smooth enamel surface (free of dental plaque).

Internal colour is the colour of the dentine. Some things we eat and drink, as I’ve mentioned contain higher levels of chromogens. Most people have enamel defects, such as recession and abrasion where the dentine is exposed. Enamel is also porous. This can cause chromogens to be absorbed by the dentine, which will darken the tooth even more. Also, as we age, through normal tooth wear and vigorous brushing, the enamel becomes thinner or is destroyed completely, and more of the dentine shines through. Therefore, the teeth take on a darker appearance. Also, as time goes by, secondary dentine is formed, making the darker dentine layer even more apparent.

Stains on the enamel can be removed by a dentist/dental hygienist who does professional cleanings. It is unlikely for you to be able to remove the stains yourself. When dental plaque is calcified (calcification occurs anything between 1 and 14 days), it is impossible to remove with a toothbrush, and can only be done professionally with the right dental instruments. When teeth whitening is performed on teeth with extrinsic staining, the result will be less visible, because the stains will still be there.

You can also have intrinsic staining/discoloration of the enamel. This is where the discoloration is within the tooth. Intrinsic discoloration can be due to medication use, childhood illness, infection, tooth trauma, high intake of fluoride and other systemic origin. These stains are very difficult to treat, and teeth whitening is not the preferred treatment. In mild and selective cases teeth whitening might bring an improvement.

Why are teeth always darker on the gum line, even after teeth whitening?

Teeth whitening does not even out the colour of your teeth. Your whole tooth will get whiter but the area of the tooth that is darker will still be darker after whining. This means the lightest part of your tooth might go five shades lighter, and the darkest part of your tooth will also go five shades lighter. The tooth is darker on the gum line because the enamel is so much thinner towards the gum line, so the underlying dentine is more visible. Often, because of too vigorous brushing or a wrong brushing technique, we create some gum recession. So, the part of the tooth that is normally underneath the gum line and where there is no enamel but only dentine, is now visible in the mouth. The dentine is always darker than the enamel.

Who should have teeth whitening done?

Teeth whitening is an excellent way to enhance your smile. Some dental defects might be less visible when the colour of the teeth is improved. It is recommended to consider the health of your teeth and gums first before doing any whitening. Teeth whitening often creates a new motivation in looking after your teeth. Anyone who wants to improve their smile, can consider teeth whitening.

Who shouldn’t do teeth whitening?

Whitening is not advised for pregnant and breast-feeding women as the effect of teeth whitening on an unborn baby or baby being breast fed is unavailable.
Children younger than 14 years should not do teeth whitening. In young children, the nerve of the tooth is located much higher up in the crown of the tooth. This will make the teeth much more sensitive during teeth whitening. By 14 years of age all primary teeth will be replaced by the permanent teeth. Primary teeth are always whiter than permanent teeth. In a mixed dentition (primary and permanent teeth), the permanent teeth will appear darker than what they actually are. Only once all the permanent teeth are erupted, should it be determined if whitening is needed.

Always ask the question: Does the child wants whiter teeth or is it important to the parent to have the child’s teeth whiter?

Patients who already have anterior (front of the mouth) crowns/veneers/composite bonding are not candidates as teeth whitening will only change the colour of natural teeth. Unless you plan on redoing the crowns/veneers/composite bonding.

Often, but not only after orthodontics, patients have “white spot lesions”. This occurs when bacterial plaque is left on the teeth for long and the teeth started to demineralize. (Hence, we always advice for patients going through orthodontics to have professional cleanings at least every 3 months.) White spot lesions mean that decay started to occur, but was arrested in time, so no cavity has formed, but the demineralisation process was severe enough to cause a chalk white stain on the teeth. Whitening will not remove these white spots. Teeth whitening will cause the rest of the tooth to become whiter and those spots will get whiter as well. So, you will be left with whiter teeth having whiter marks on them.

Am I too old to have my teeth whitened?

There is no such thing as too old when it comes to teeth whitening. It’s a personal choice and although ageing is a part of life, at least we can enhance the colour of our teeth. So why not? Am I too old to have my teeth whitened

When shouldn’t you have teeth whitening done?

If you’re considering having teeth whitening done for a special occasion, don’t do it the day before. Some people experience temporary sensitivity that might get in the way of enjoying your special occasion.

Avoid having whitening done for at least 2 weeks prior to composite bonding. There’s an interaction with the chemicals of teeth whitening and the bonding agent used in composite bonding.

If you’re due to do a whitening maintenance application, don’t do it the day before you have your professional cleaning, as the teeth might be slightly sensitive for the first day after whitening.

If you’re wanting to have dental work done, especially in the front of your mouth, firstly decide if you are happy with the existing colour of your teeth. If not, then this is the time to do whitening before you continue with crowns, veneers or composite bonding. So often, we have patients who had extensive work done on their teeth and when it all is completed, the patient then wants their teeth just a shade or two lighter. Unfortunately, only natural teeth will change colour.

Is teeth whitening effective?

I’ve never seen a patient have no response to teeth whitening. It is highly likely that you will get some improvement of the colour of your teeth. But, it is impossible to predict how many shades lighter your teeth will be. Some products are more reliable and effective than others. My advice is to always choose a product that is tried and tested and has been on the market for long and is recommended by your dentist/dental hygienist.

How much does it cost?

In-chair teeth whitening is more expensive than an at-home whitening system. The special LED light that is used with an in-office treatment can be a large expense, and provision for chair-time needs to be considered.

Are there any side effects of teeth whitening?

Some patients experience temporary sensitivity. This can last for 24 hrs. When doing at-home teeth whitening, the sensitivity might last longer because you will typically do whiting for consecutive days, until you reach the desired result. Normally this can be anything up till 2 weeks, but in selective cases, the patient might be instructed by the dental professional to do the whitening for a longer period. Your gums might be tender after teeth whitening. This should not be the case with in-office whitening, as the gums are blocked out completely. It might be the case with at-home whitening, when too much whiting agent is put into the trays. As dental professionals, we try our best to give adequate instructions to prevent this from happening. A small number of patients experience some sensitivity towards the end of the in-office whitening appointment. But mostly the sensitivity becomes apparent after the whitening process is completed.

How long does the result last?

If you do maintenance, you will keep your result. Once you’ve done your initial teeth whitening and the desired result has been achieved, you can easily and effectively maintain the result with one application every 30 days or so. The maintenance is done with custom made trays. The dental professional will take impressions of your mouth prior to your in-office whitening appointment, and have trays made for you. These will fit snugly and are custom fitted to ensure the whitening gel will not leak out onto the gums. It doesn’t mean that you will see a decline in colour in 30 days, but the aim is to keep the result. If no maintenance is done, your teeth will gradually get darker with time.

Are all teeth whitening gels the same strength?

There are different strengths of peroxide. It varies from 6% up to 25% and in some countries up to 35% is allowed. The different types of peroxide are hydrogen peroxide and carbamide peroxide. Hydrogen peroxide breaks down faster than carbamide peroxide, so it releases most of its whitening power within 30-60 minutes. Carbamide peroxide releases about 50% of it whitening power in the first two hours and can remain active for up to 6 additional hours. Therefore, hydrogen peroxide is normally used for in-office whitening procedures, and carbamide peroxide for at-home whitening procedures. The different strengths will determine how fast the product works, therefore for how long you need to apply the whitening gel. A low concentration of carbamide peroxide will need to be on the teeth for longer.

What about over-the-counter whitening products?

Caution needs to be taken when considering over- the- counter teeth whitening products without consulting with your dental professional. The health of your teeth is the priority – please get advice from your dental professional before making your decision. Often over -the- counter products are less effective because of the low concentration of carbamide peroxide and not all of them are endorsed by the dental profession. Make sure to always use a product that has sufficient research information and that has been on the market for some time.

What is the difference between in-office teeth whitening and at-home teeth whitening?

In-office whitening is done in the dental office by the dentist or dental hygienist. If you don’t experience any sensitivity while doing the procedure it can be done in one visit of approximately 90 minutes. This means you will instantly see a result. If you do have some sensitivity, the sessions can be broken down into 2, 3 or 4 X 15-minute sessions. It is recommended to do maintenance applications after an in-office procedure. Maintenance is typically one at-home session every 30 days. Custom made tray will be made and given to the patient to be able to do the maintenance. The biggest advantage of in-office teeth whitening is that the result is instant. The biggest disadvantage is that it is more expensive than at-home teeth whitening. What is the difference between in-office teeth whitening and at-home teeth whitening

At-home whitening is done by the patient at home. The whitening gel is applied daily for a week or two and there is a gradual change of colour of the teeth. If the teeth feel too sensitive after a few days of whitening, the patient can skip a day or two and wait for the sensitivity to decrease before continuing again with the whitening process. Just like the in-office option, maintenance is recommended to maintain the lighter colour of your teeth. Maintenance is typically once every 30 days or so after the initial whitening for a week or two. The biggest advantage of at-home teeth whitening is that it is much more affordable. The biggest disadvantage is that you need to be patient, because the desired result is only achieved after a week or more.

What is laser teeth whitening

All in-office teeth whitening procedures are done with hydrogen peroxide. Whether the activator is an LED light or laser, they activate the peroxide for it to work faster. Without peroxide, no LED light or laser will whiten your teeth. The function of an LED light or laser is to create light and heat to activate the peroxide. This allows the peroxide to break down faster, and create the free radicals that whitens the teeth. Without this light and heat, the whitening process will still happen, but much more slowly. Therefore, an in-office whitening procedure will be done with either an LED light or a laser and the result immediate. At-home whitening, without the use of an LED light or laser’s light and heat, will take a couple of days to achieve the same result.

What happens if I ingest some of the whitening gel when I do at-home teeth whitening?

At the most, you might have a little irritation in your throat, or an upset tummy and in rare cases some vomiting. It is unlikely that you will ingest a significant amount of product and have these reactions when you use at-home whitening trays from your dentist or dental hygienist. The trays fit snug around the teeth and are custom fit for your mouth. Furthermore, a lot of effort is put in, giving comprehensive instructions of how to use the product at home. Because the whitening trays fit so snugly around the teeth, it’s very difficult to fit in a substantial amount of whitening gel. This is not the case with over-the-counters products–you will not have a custom fit tray and it’s easy for the whitening gel to leak out. You also need to use a lot more whitening gel in the one-size-fits-all trays.

Can I drink tea, coffee and red wine or smoke after I’ve whitened my teeth?

It is recommended, that for 24 hours after teeth whitening, you do not eat or drink any dark coloured food and drinks or use tobacco products. The pores of the enamel are wide open after the whitening procedure and takes 24 hours to close. Thereafter you can eat and drink as normal. If you drink a lot of tea, coffee and red wine, it might be wise to try and cut down a little on frequency or amount. This was the reason why you had the whitening done in the first place. If you’re a heavy coffee, tea and/or red wine drinker and/or a smoker, you want to do your maintenance more often than every 30 days. But, it doesn’t mean that you need to stop drinking any of the above-mentioned drinks or stop smoking after teeth whitening.

What to expect from an in-office teeth whitening procedure?

If you do 4 X 15 minutes application, plus the time to prepare the mouth, the session might feel quite long—it will take 90 minutes. You might get bored so make sure to take some entertainment such as ear pods or an audio book.

Usually no sensitivity is felt during the procedure. If you do experience some sensitivity, it’s more than likely to be towards the end of the procedure or afterwards. This is temporary and will be gone within 24 hours. Try not to schedule your appointment on a day when you have other social commitments. You will be instructed not to have a diet rich in dark colours for the first 24 hours.

How is the in-office procedure done?

For the best results, have a dental health check and cleaning done to make sure that all your teeth are without decay and external staining is removed.

At this appointment, impressions of the mouth will be taken, and maintenance trays will be made. These trays will be given to you at your in-office whitening appointment.

Make sure you’ve eaten a substantial meal on the day of the whitening appointment. You might have some sensitivity afterwards, and not feel like eating for a few hours. Your dental professional will give you a short explanation of the procedure, what to expect and make sure you are comfortable.

The first step is to insert a flexible, plastic mouthpiece keeping the lips and cheeks away from the teeth. Then a protective barrier is placed over the gums. This is to protect the gums from the peroxide that will be used on the teeth to prevent them becoming sensitive. How does Teeth Whitening Work at a Dentist Office?

You will receive protective eyewear to shield your eyes from the LED light. The peroxide is applied to the teeth in 15-minute intervals. After the peroxide is applied, an LED light is switched on to shine onto the teeth. After each 15 minutes, the peroxide is removed from the teeth and an enhancing gel will be applied before peroxide is applied again for the next 15 minutes and the light shines onto the teeth again.

After 4 applications, the procedure is complete, the last peroxide is removed, and the protective barrier and mouthpiece is also removed.

Instructions on your diet for the first 24 hours will follow, as well as the instructions of your maintenance regime. You will also receive your whitening trays and material and some desensitising gel for the first 24 hours, in case you develop sensitivity.

A smile is most attractive accessory you can wear. When we smile, we create instant happiness for ourselves and those around us. By even slightly enhancing of the colour of your teeth, your smile can be even more beautiful.

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