Teeth whitening at home: methods and reviews. Is teeth whitening harmful? Is it necessary to whiten healthy teeth?

Before whitening, you should think carefully: do you need this procedure and are you ready for the accelerated development of caries?

The method of "home" teeth whitening in the 4th dental clinic in Minsk

Comment 21 on the note “Teeth whitening. Who can whiten their teeth? "

Laconic, useful, great!
Thanks.

But after all, some people have darker teeth by nature, and not because of deposits. Do abrasive substances help here too?

I dare to suggest that abrasive substances are useless in this case. After all, the principle of their action is to erase the top layer (this makes sense, for example, when removing rust from a product).

True, it is still better to ask the dentist why the teeth are dark.

short and clear 🙂

Whitening, implying only the removal of dental deposits (ultrasound, chemicals, instruments) is not exactly whitening - it is just the removal of dental deposits 🙂 ... The procedure is necessary and important - it prevents the development of caries ...

Whitening is usually just understood as "internal" tooth whitening ... They use chemical. substances, the simplest of which is hydrogen peroxide. The rest are known to me from chem. properties are very close. This procedure cannot be useful by definition, the effect is purely cosmetic.

I would like to whiten my teeth, they are yellow, as long as I remember them !!! but there are fillings in the front teeth and more than one! what to do in this situation ???

The most logical thing is to consult a dentist ...

Hello! Please tell me, here I am a smoking person, but let's say I can stand it for 3 days without smoking. I have a wedding and I would like to whiten my teeth for a short amount of time, can I have something generous? I heard that teeth can be covered with enamel, it will be temporary!

If you take care of your teeth and do not want to damage them, it is necessary to whiten your teeth at the dentist. And therefore, he should also choose the method of whitening.

It is clear that in order for the whitening agent to reach the tooth, the tooth must be clean, without tartar, plaque, fluoride varnish. At home bleaching the concentration of the whitening agent is between 3% and 22%. It takes many days to get a SUPER result. At professional whitening concentration from 35% and more: it is necessary to protect the gums and soft tissues of the oral cavity. SUPER result (not always guaranteed ... for 1 visit) in 1 hour.

Special lamps or laser, special catalysts are used. + everything is very individual. After high-quality professional whitening and a very “long-term home” bleaching, the original color in people with excellent oral hygiene (you smoke or drink coffee, juices, etc.) does not return. The new color may, however, fade slightly.

About sensitivity your teeth: everything is very individual. Decide here with your doctor. Even if the teeth are initially insensitive, analgesics may be needed for several days immediately after whitening. Sensitivity, however, is reversible in such cases.

Diabetes mellitus, enamel cracks, cancer, under 16 years of age (? ... ..), periodontal diseases are not contraindications for teeth whitening... Everything else is correct.

Whitening systems affect the organic matrix of the tooth. The structure of hard tissues does not change, the teeth do not become weaker.

Does the organic matrix affect the "strength" of the tooth? 🙂 Is there a link to clinical trials?

in addition, whitening will not help in the case of "tetracycline teeth" - if the patient took tetracycline in childhood. this drug changes the color of dental tissues.

Hello! I have 20-30% of the anterior incisor, the rest of the tooth is a photopolymer filling reinforced with a fiberglass pin. The part of the tooth, where the living tissue remained, turned very yellow and clearly differs from the filling. Tell me, is it possible to apply surface whitening? Because I don't really want to use the in-ear channel.

living in general is harmful ... 🙂 and little white teeth look great, adorn a smile and improve well-being)

and I always use whitening pastes, my teeth become whiter and all are intact for now)) I buy Roks pastes, I like them because they bleach well and there are few abrasive substances in them compared to other pastes.

Pastes really help, but you need to use them regularly, and not from time to time, otherwise there will be no effect. In this regard, I like Mexidol dent, it bleaches well.

hello, please help me, I decided to whiten my teeth in dentistry, I already had fluorosis, the doctor said that they can whiten by 2 tones! after whitening, the stains on the teeth did not go away! bleached polyester as the doctor told me! What should I do now? Can I get a refund if there is no effect?

The visible part of the tooth or crown consists of enamel and dentin. Whitening is the process of applying a certain composition (gel) to the teeth, which penetrates into their hard tissue (dentin).

The color and transparency of the tooth depends on the shade of the dentin, so the task of the tool is to split it into intermediate products that are lighter than the original ones.

Enamel is a translucent shell of the tooth, in order to reach the dentin and brighten it, the gel makes tiny pores in the enamel, which overlap over time. But there are times when the enamel is not restored, and grooves are formed on it, and sensitivity also increases. Laser whitening occurs in the same way, only laser beams are used instead of gel.

It can be concluded that whitening is harmful and can damage the enamel, especially for those with sensitive teeth.

Contraindications

Tooth enamel is incapable of regeneration, so it is important to know that not all teeth can be whitened without harm to health... To avoid mistakes, it is necessary to study the contraindications:

age is younger than 20 years, since before this age the enamel is not yet fully formed;
periodontium, caries, pulpitis;
allergy to individual components in the gel;
pregnancy, lactation;
high sensitivity;
increased abrasion of teeth;
crowns and fillings on the front teeth may change in color;
teeth with congenital disorders of enamel and gray shades are practically not amenable to whitening;
period of diseases.

Whitening at home

Perhaps the most budgetary and widespread method, but it requires care, since often people rely more on their own intuition, ignoring the rules and regulations. There are the following methods:

Professional whitening

For people who want to keep their dental health as safe as possible, dental whitening is the best option. Professional whitening is divided into mechanical and chemical.

Mechanical whitening

Mechanical bleaching is a prerequisite before chemical bleaching and does not cause any harm to the health of the enamel, and even is useful... The procedure helps to get rid of caries, stones and is the prevention of gum diseases such as periodontitis and periodontal disease. For healthy teeth, it is recommended to carry out once every six months, and in case of inflammation, once every 3-4 months.

This procedure consists of 4 stages:

Chemical bleaching

This type of whitening is expensive and associated with high risks, since can cause irreversible harm... Even in dentistry they cannot guarantee a 100% result and there are enough cases of not getting the promised effect. The method requires mandatory prior consultation with a dentist. Chemical whitening can be recommended if the teeth were previously white, but turned yellow with age, as well as when one or more teeth are discolored. There are the following types of chemical bleaching:

With the help of the gel in the mouthpiece.
With a laser.
Photobleaching or lamp.

Is gel teeth whitening safe?

In this type of bleaching, the active ingredient is hydrogen peroxide. When the gel comes into contact with the enamel, active oxygen is released, resulting in whitening.

Advantages:

if you strictly adhere to the instructions, you can achieve good results;
takes little time (modern gels should be kept for 1-2 minutes).

Disadvantages:

it is difficult to predict exactly how long after the harmful effects of the interaction of hydrogen peroxide with the tooth tissues will appear (in some it occurs after the first procedure, and in others in 2-3 weeks);
the acid that is part of the gel has a negative effect on the enamel;
sensitivity appears;
vitamins and minerals are lost.

Is laser whitening safe?

The procedure consists in the fact that a special gel is applied to the teeth, and the laser beams create a chemical reaction that leads to discoloration.

In this case, hydrogen peroxide is also the basis. This technique considered safe, since it rarely leads to negative consequences due to the speed of the conduct.

Advantages:

saving time;
effective result;
the possibility of multiple procedures over time;
no harm to enamel due to the speed of the procedure;
no heating.

Disadvantages:

in rare cases, increased sensitivity;
sometimes causes pain.

Is Photo Whitening Safe

Today it is a very common technique. The principle of operation is the same with the previous method, the only difference is that a polarizing lamp is used instead of a laser.

Lamp beams are more harmful than laser beams, as they heat up the enamel. Having done photo-whitening, the patient runs the risk of spending money on recovery to a greater extent than on the whitening itself. This type takes place only in the case of a strongly pronounced darkening.

Advantages:

small price in relation to laser whitening;
good result.

Disadvantages:

the patient's enamel heats up;
the application of the gel is carried out several times per session;
too concentrated gel composition;
enamel is destroyed;
painful sensations;
increased sensitivity;
the possibility of stains on the teeth is possible.

Is teeth whitening harmful in dentistry?

Summing up, we can conclude that the safest type of bleaching is mechanical, since it does not harm at all and even treats various diseases such as tooth decay or periodontal disease.

The secret lies in the fact that the main effect is carried out on the deposits on the surface of the enamel. At the same time, no substances penetrate into it. If the patient wants to get a more impressive result and has decided on the chemical method, then it is best to choose the laser one, since it has practically no side effects. A good option would also be the use of home systems, which are selected in dentistry individually for each person.

How to minimize the harm from procedures

First you need to consult an experienced specialist in reputable dentistry or a dentist that the patient trusts. Only in dentistry will they be able to determine all contraindications, identify diseases or possible allergic reactions to the components of the drugs.
If the patient decides to undergo chemical whitening, it is imperative to do a preliminary mechanical cleaning.
If any diseases are present, then from the beginning you need to completely recover.
In order for the whitening effect to be maximized, it is necessary two weeks before and after stick to a white diet... It consists in the use of mainly white products, which contain a minimum of dyes. Red vegetables and fruits, red wine, as well as coffee and tea are excluded from the diet. If the patient smokes, one should refrain from the addiction.
Since chemical bleaching is associated with great risks, don't use cheap drugs, they can burn the enamel.
Doctors recommend performing restorative procedures after direct bleaching, such as remineralization or fluoridation.

As simple as this procedure may seem, you should prepare in advance. And only a qualified dentist knows what exactly needs to be done for this. First of all, you cannot avoid professional cleaning that removes plaque and stones. Otherwise, whitening will not help. Of course, all carious cavities should be healed and chronic diseases should be brought into remission.

In preparation for whitening, your doctor will likely prescribe remineralizing therapy, show you how to brush your teeth properly, and tell you which foods to avoid.

Tea, coffee, beets, dark berries, red wine have an enamel-coloring effect.

A colorless diet within a week after the procedure is especially important, otherwise the effect will be the opposite of the expected one: the dyes will easily penetrate under the porous enamel, and after its restoration it will be much more difficult to remove them from there.

And of course, if you smoke, teeth whitening seems like a very dubious undertaking. If you do not give up this addiction, the enamel will soon darken again.

Are there any contraindications for teeth whitening?

The procedure will not be carried out for children under 16 years old, as well as for pregnant and lactating women. Increased abrasion of teeth, periodontitis, periodontal disease and other gum diseases call whitening into question. In addition, among the contraindications are unhealed caries (if the whitening gel gets into the carious cavity, you will experience severe pain) and wearing. And if you correct the bite with the help of aligners, then nothing prevents you from resorting to home professional whitening.

If you suffer from tooth hypersensitivity, then you probably should not do bleaching, as it itself can provoke this problem. However, with appropriate preparation - with remineralizing therapy before and after fluoridation of the enamel - whitening is possible. But only after consulting a doctor and with his consent.

Is there a difference between home and office whitening?

First of all, you should divide whitening into professional and non-professional. Professional can be both office (office) and home, or it can combine both of these stages.

It is important to understand that in-room whitening has a more aggressive effect: gels contain 30 percent or more of active ingredients (carbamide or hydrogen peroxide), while homemade gels work more sparingly, but, of course, not so quickly. They contain 7-10% hydrogen peroxide and 16-22% carbamide.

The doctor decides which whitening to recommend for you, evaluating the condition of the oral cavity and general health. That is why we do not recommend buying whitening systems for home use at the pharmacy on our own. And if you have already purchased one, be sure to show it to your dentist in order to avoid complications: hypersensitivity of the teeth, inflammation of the gums,.

Unfortunately, even in the case of in-office whitening, the result is unpredictable: it depends on the individual characteristics of the organism and existing chronic diseases.

For example, teeth of patients with fluorosis are practically not whitened. Such patients are recommended restoration: veneers, lumineers, crowns.

Are there any benefits of home whitening?

First of all, it is worth highlighting the price: it is often significantly lower than the cost of in-room whitening. In addition, home whitening is more gentle. But you have to be. Once or twice a day for several weeks, you should put on a mouth guard and wear it for the prescribed time. Otherwise, the desired effect cannot be achieved.

If you are not confident in your abilities or want to get serious results in a short time, consider the salon option.

Are folk remedies effective?

In order to explain why folk bleaching agents do not work, you need to understand the meaning of the salon procedure. And it does not affect the enamel of the teeth, but the dentin - the soft layer located under the enamel. Folk remedies for teeth whitening simply cannot penetrate so deeply and act on the surface. The enamel itself is transparent, but the plaque accumulating on its surface can be colored stronger or weaker. It is with him that salt, soda, activated carbon and calcium gluconate fight.

Some of the folk remedies are innocent, others, such as soda, can seriously scratch the enamel, because these are abrasives that literally rip off plaque from the surface of the tooth.

Yes, teeth sometimes brighten, but only as a result of getting rid of plaque, nothing more. And if you thoroughly paste, brush, floss, use a rinse aid and regularly visit the dentist for preventive purposes, then you will not even notice the result of such a folk procedure.

Separately, it should be said about hydrogen peroxide. Yes, it is used in both salon and home remedies for whitening, but in a gel it is not more than 10% in combination with caring, restorative and analgesic components that can reduce tooth sensitivity. Pure peroxide can severely burn the mucous membranes of the mouth.

If you still want to take advantage of folk advice, we can recommend rinsing with very strongly diluted lemon juice, applications from lemon zest, strawberry or strawberry puree. However, do not expect miracles from them. These funds will not be able to significantly whiten teeth.

Teeth whitening is a serious procedure that requires a detailed examination of the entire oral cavity, which can only be performed by a doctor. You should not self-medicate in any case, especially when it comes to teeth, because many problems associated with digestion or even the spine are caused by an incorrect bite, increased abrasion, and enamel defects.

Folk remedies and systems for whitening, bought uncontrollably at the pharmacy, may not only not help, but also harm the teeth. And if you don’t take care of your oral cavity: you don’t visit a hygienist once every six months, smoke, drink a lot of tea and coffee, brush your teeth poorly, then even salon whitening can only bring frustration.

With improper care of the teeth and oral cavity, they eventually begin to darken and acquire a yellow tint. Strong coffee, tea, smoking have an effect on the color of teeth. When there is a desire to whiten the enamel, it should be taken into account that the enamel will become lighter, but the filling material will not. After bleaching, small fillings can be replaced or, after removing the top layer, cover with a new one, matching the tone in accordance with the color of the enamel. Over time, the enamel will darken again, the fillings will again differ from it.

Expert opinion

Biryukov Andrey Anatolievich

doctor implantologist orthopedic surgeon Graduated from the Crimean honey. institute in 1991. Specialization in therapeutic, surgical and orthopedic dentistry including implantology and prosthetics on implants.

Ask an expert

I think that you can still save a lot on visits to the dentist. Of course I'm talking about dental care. After all, if you carefully look after them, then it really may not come to treatment - it will not be necessary. Microcracks and small caries on the teeth can be removed with ordinary toothpaste. How? The so-called filling paste. I single out Denta Seal for myself. Try it yourself.

If the teeth are healthy and strong, then you can lighten the enamel from 2-10 tones. There are chemical, ultrasonic, laser, photobleaching. The Air flow procedure involves high-quality cleaning, during which the enamel lightens by several tones. The procedure is contraindicated for asthma, bronchitis, during pregnancy. There are other restrictions, a doctor's consultation is necessary.

After whitening, teeth appear spotty if the fillings are large. The problem can be solved by placing on the front teeth. Pulpless teeth differ in yellowness from other teeth. The doctor applies a solution to the dead tooth, sodium perborate into the enamel for clarification, to speed up the process, a light-thermal radiation device is used.

Do you feel anxious before visiting the dentist?

YesNo

There must be clinical indications for the whitening procedure. There is a risk of teeth demineralization, occurrence. Lightening procedures are carried out for 6-7 weeks.

How to bleach

Before you start whitening, you need to sanitize the oral cavity and fix the problems. Whitening can not be carried out when. It is necessary to cure the teeth, replace the old fillings that have stood for more than 2 years. The lightening solution will get into the formed gaps, it will corrode the tooth from the inside.

Professionals will carry out whitening in stages:

cleaning - the dentist cleans teeth from soft and hard deposits (tartar);
whitening procedure;
restoration of old fillings with the replacement of the top layer with a new one (of the appropriate tone).

It is necessary to contact a hygienist for cleaning once every six months or a year to preserve teeth. Doctors do not recommend whitening of filled teeth, the procedure increases their sensitivity and weakens enamel. After undergoing whitening, brush your teeth (which have become hypersensitive) with a new (soft) brush with whitening paste.

Do fillings whiten

After teeth whitening, in the presence of fillings, the enamel will brighten, but the fillings will not. Fillings in the smile zone will become especially noticeable. Photopolymer filling allows for whitening. Low-quality fillings cannot be whitened. Having removed the top layer of the filling, the doctor can replace it by choosing the desired color. Whitening will be needed again over time.

You can get a beautiful smile with large fillings, or by making veneers.

Thin porcelain (or made of composite) plates are applied to the front teeth, hiding all flaws (shape irregularities, spots). They replace enamel, giving beauty and outer shine to a smile, never darken.

Whitening contraindications

Whitening procedure is contraindicated:

minor children;
pregnant women;
allergy sufferers to bleaching ingredients (carbamide, hydrogen peroxide);
people with hypersensitivity of the teeth;
wearing braces;
having many fillings;
suffering from periodontitis, caries;

The procedure cannot be done six months after tooth extraction, with a pulp chamber in the tooth.

The procedure is useless for smokers, the whitening effect will quickly disappear. After cleaning, you need to refrain from coffee, strong tea, coloring products and smoking (at least 3-5 hours).

Side effects of teeth whitening

During the procedure, irritation of the oral mucosa (gums, cheeks, palate) is possible. The means are used caustic, the doctor applies a protective gel, puts rubber pads on the surfaces surrounding the tooth.

To make the process safe, no anesthesia is done during the procedure. There may be discomfort, pain, which must be reported to the dentist in order to prevent chemical burns.

After completing teeth whitening, there may be side effects:

sensitivity to hot and cold (stabbing impulse pains);
twitching and aching (breaking) pains;
redness of the gums.

Unpleasant manifestations persist after a couple of days. During the recovery period, you can use pastes that reduce the sensitivity of the teeth, apply a fluoride gel to the enamel. To relieve discomfort, you can take Ibuprofen, Voltaren.

Whitening at home

There are ways to whiten your teeth yourself. Dentists do not like these products. They recommend, without first consulting a doctor about the health of teeth and oral cavity, such procedures not to be used:

To maintain the whitening effect, it is recommended to brush your teeth 2 times a week using a stiff bristled brush and whitening paste. You can apply and hold the paste for 5-10 minutes, then rinse your mouth.
Apply the mixture (2 teaspoons of 10% peroxide with 2 drops of ammonia) to the teeth and hold for a few minutes. The mixture whitens without destroying the enamel.
Apply lemon juice on the teeth with a cotton swab and hold for 15 minutes. Instead of lemon, you can dilute 1 g of lemon to-you in 1 tsp. water. The procedure can be done 2 rubles / day.
Soda cleans and brightens teeth. Mix baking soda with water, apply the mixture (paste consistency) to the brush and clean.
Enamel that has darkened from smoking, drinks (black tea, coffee) can be lightened with chewing gum with whitening ingredients.
It is useful to rub the teeth with the inside of the banana peel. The peel contains micro and macro elements (potassium, phosphorus, calcium, etc.), which help to whiten the enamel.

If home methods did not help to lighten the fillings on the front teeth, you will have to resort to the help of a dentist who will try to do it professionally. A sensible solution is to apply a new layer of color to the filling.

After enamel bleaching procedures, do not consume vegetables and berries with a coloring effect (beets, carrots, blueberries), refrain from coffee, strong tea, and chocolate.

Prevention after whitening

To maintain healthy gums and teeth, hygiene procedures are essential every day. Use a brush and dental floss to get rid of plaque and food debris. The remaining plaque forms tartar, which favors the development of bacteria.

Over time, the inflammatory process spreads deeper, affecting the gums and destroying the teeth.

It is necessary to do hygienic cleaning by a professional. The dentist will remove tartar and plaque from the corners gently and painlessly, which is impossible to do. Only a doctor can remove tartar in the hard-to-reach supragingival area that is vulnerable to infection. Teeth polishing is a cleaning procedure that reduces the risk of calculus formation. The professional cleaning procedure is important for maintaining healthy teeth and oral cavity, is a preventive measure against periodontitis, caries.

In order for the cleaning result to last longer, you need to maintain oral hygiene at home at home:

brush your teeth correctly (in the morning and before bedtime), the use of supersonic brushes gives the best cleansing effect;
to clean the interdental spaces, it is recommended to use dental floss, irrigators (water pulsation devices) and special brushes (electric brushes with different attachments);
use rinses. There are many rinse aids on the market today. Use (1-2 rubles / day) will help eliminate bad breath, strengthen the gums, tooth enamel. However, their choice must be approached carefully, in consultation with a dentist. If the composition contains a disinfectant chlorhexidine, it can be used for a short time to combat periodontitis in a neglected form, with an acute oral infection. For many people, mouthwash can have side effects.

Natura Siberica rinses are popular and harmless, they have a bactericidal effect, are created from natural ingredients and essential oils, are recommended for daily use, have no contraindications.

From a huge list of different rinses, a dentist will help you choose the one that is useful for you, taking into account its composition (components) and effects (from caries, infection, inflammation of the gums): Elmex. PresidentKlassik Plus, Lacalut Aktiv, Paradontax.

Many people think that teeth whitening is harmful and dangerous. But is it really so? What is the least harmful and most effective way? Let's figure out the situation once and for all.

There are four main groups of teeth whitening methods.

Mechanical. This type includes the usual hygienic cleaning of the teeth in the morning and evening, and a professional service in the dentist's office.
Abrasive. Most often, unconventional and folk recipes are ranked among these types of cleansing. For example, using activated charcoal gruel or peeled banana peels. Such methods allow you to whiten the enamel for a couple of tones, but their effectiveness is short-lived.
Chemical. The most commonly used group. This implies the use of hydrogen peroxide and its derivatives. This category includes the most effective, but also the most dangerous methods.
Combined. Combines the properties of several groups disclosed above.

Teeth cleaning is a mechanical type The use of charcoal is an abrasive method Chemical is a bleaching with hydrogen

Oksana Shyka
Dentist therapist
Surprisingly, the most effective procedure is also the safest. This is an ultrasonic teeth whitening using the Air flow apparatus. It gently cleans the enamel and in one application returns the tooth enamel to its original shine. True, creating a snow-white Hollywood smile in this way will not work, because this technology refers to abrasive methods and does not affect the internal tissues of the tooth.
Air flow cleaning is considered to be a very effective and safe way.
Feature of chemical enamel brightening

Peroxide is a potent carbamide or hydrogen acid that penetrates dentin and changes its structure. As a result, the transparent layer of the tooth changes and becomes white. The final result and its preservation period depend on the duration and frequency of the procedure, as well as on the strength of the catalyst used.
Oksana Shyka
Dentist therapist
Using this method, you can whiten your teeth to a snow-white shade. However, this will cause serious damage to the oral cavity.
During the procedure, peroxide penetrates the dentin through the enamel, disrupting its integrity. The substance has a huge effect on teeth:
Enamel. It is damaged due to exposure to acids. This is especially dangerous with constant, long-term and over-catalytic action.
Dentine. Under the influence of peroxides, bone tissue necrosis occurs, due to which the color changes from transparent to white. In return, the dead tissue does not receive additional nutrition in the form of minerals and vitamins and is quickly destroyed.
Nerve endings. Due to dentin necrosis, nerve endings can be pinched inside the bone. This causes chronic toothaches. In addition, exposure to acids negatively affects the sensitivity of the nerve, causing internal burns, thereby temporarily increasing the sensitivity of the tooth to the limit.
Gums. Peroxides, as powerful acids, can cause severe burns to the mouth and gums.

Too frequent bleaching has a negative effect on enamel and gums
It is important to know

Before using any method, you should consult with your dentist. Most often, ultrasonic is sufficient to achieve the optimal effect.
Among the chemical agents for enamel clarification, LED is considered the most effective and safe. It is also the most expensive. The LED allows you to minimize the effect on tooth enamel and accelerate dentin ossification. So, despite the high damage to the inner layer of the tooth, the nerve endings and enamel remain intact, which allows you to keep your teeth relatively healthy for several years.
LED Whitening Machine
Oksana Shyka
Dentist therapist
It is recommended to carry out professional chemical clarification no more than once every five to seven years. This is exactly how much the body needs in order to replace all cells, including damaged areas in the oral cavity. But mechanical and ultrasonic cleaning can be carried out up to several times a year.
Whether it is worth doing the procedure is up to you. In the video below, the dentist tells if teeth whitening is harmful:
The harm of one-time whitening with accompanying factors can be almost invisible. But the frequent procedure is dangerous to the health of the oral cavity. Remember that repeated bleaching with peroxides has less effect than the previous one, but a greater risk of occurrence and formation of side effects.