Dra. Marília Freitas

Médica Dentista · Dentist

Teeth whitening

HPA Magazine 17

Facial aesthetics has an influence on social behaviour and an impact on the perception of our society. Currently, Aesthetic Dentistry is one of the main focuses of our daily practice. The search for a whiter and more harmonious smile results in psychological and emotional well-being for the patient. Literature describes that dissatisfaction associated with alterations related to dental colour, varies between 18% and 53%. This dissatisfaction is observed in about 40% of individuals between the ages of 16 and 54 years. 

Tooth Colour
Firstly, the pre-conceived idea of most patient that teeth colour depends on the colour of tooth enamel is not true. Teeth colour derives form dentine the underlying layer of enamel and not from enamel itself. Therefore, patients who wish to have whiter teeth must be aware that this is not always possible. However, enamel can vary in colour, from pale yellow to greyish white or even bluish white.
Dental aesthetics is considered to have “four fulcrums”: the three-dimensional shape of teeth; colour that is a psychologically perceived sensation; primary optical properties (hue, saturation and luminosity, integrated in the concept of colour) and secondary optical properties (fluorescence, opalescence, translucency (opacity), iridescence and surface gloss).
Tooth Whitening
There are currently two tooth whitening techniques: the outpatient technique and the intensive dental surgery technique, with and without light source activated photosensitive agents.
Outpatient whitening is indicated for cases where teeth are naturally darkened or darkened by pigments acquired from the diet, in smokers, in older patients mainly, to avoid prolonged time in the dental chair, in traumatized or affected teeth due to the use of medication such as tetracycline and dental fluorosis.
The big advantage of this technique is its compatibility with soft tissue and its lower cost. The main disadvantage is the length of time needed for the treatment, which is a factor of great relevance for many patients, who often opt for the intensive technique at the dentist, thus obtaining immediate results. Another disadvantage is the need to produce a mould for the patient's mouth to obtain individual trays for the application of the product. These trays accommodate the bleaching agent that contains carbapol, providing a slower release of oxygen, requiring 6 to 8 hours to act. Suitable to be carried out at night.
With the laser tooth whitening technique carried out in the dental surgery, 6% to 40% concentration hydrogen peroxide is used, which is light and/or heat activated, causing an increase in the release of oxygen, which is safer and more comfortable for the patient, where visible results are obtained with just one session. The association of light sources results in less time needed, since when the light is projected onto the gel, a fraction of it is absorbed, and this energy is converted into heat, accelerating the release of peroxide hydroxylic radicals.
However, the effectiveness of this technique is still not consensual despite the physicochemical interaction of light with the whitening compound being known. Clinical results acquired in a single session, may not be durable long term due to the instability of tooth colour.
A few months after treatment there may be a relapse to the original colour.
Another known disadvantage is that it might be potentially harmful to soft tissue. Its cost is also higher. 
A third possibility is combined whitening, which reconciles the two types of tooth whitening: a whitening session in the dental surgery for a more effective and quick change in the initial colour of the teeth and, subsequently, the treatment is complemented using the bleaching process at home, to obtain the desired final result. This practice reduces the total treatment time and gives a greater longevity to the final whitening result.
The greatest advantage of associating the two methods is that it allows tooth whitening touches and provides the patient with a longer-lasting effect.
Selecting the tooth whitening method should be based on the number of stained teeth, type of discoloration, severity, vitality of the tooth, tooth sensitivity, time available, cost and the patient's cooperation.
Tooth colour alterations 
Some have classified tooth colour changes as extrinsic and intrinsic.
The extrinsic ones are more frequent and superficial. They occur due to the abusive consumption of substances such as coffee, tea, some soft drinks, dyes, poor oral hygiene, use of some medication and tobacco. Intrinsic causes are more difficult to treat and can be congenital, related to tooth formation or acquired. They may also be related to trauma, pulp necrosis, extensive restorations, caries or fluorosis.
Tooth whitening contraindications 
There are some contraindications and/or restrictions for this treatment, namely patients under the age of 10 years, patients with xerostomia (dry mouth due to low saliva production), lesions in the oral mucosa, tooth hypersensitivity, large amount of restorations, irritated gums, pregnant and lactating women, alcoholics and smokers. The latter have a major limitation to tooth whitening effectiveness, however it is not explicitly contraindicated.
In these cases, the ideal is for the patient to significantly reduce or stop smoking before starting treatment.
The continued consumption of tobacco during and after treatment may lead to colour alterations in a short period of time, leaving the patient dissatisfied with the final result.
Another cause of extrinsic pigmentation is the prolonged use of chlorhexidine, an antiseptic and antibacterial agent widely used in Dentistry, the use of this agent should always be recommended by your Dentist.
The effect of teeth whitening
Enamel is subject to constant changes, from physiological wear to changes in its morphology.
The most frequent question asked by patients is: "does whitening weaken the teeth?" Searching for answers in the current specialty literature, we find that some studies  support the hypothesis that whitening agents are chemically active components potentially capable of inducing structural alterations to the surface of the enamel, while other studies report that no significant changes were observed.
Thus, it is not yet possible for us to draw a definitive conclusion, since the literature is still not consensual regarding adverse effects.
Sensitivity after tooth whitening 
Sensitivity after a tooth whitening procedure has been considered a common adverse effect, together with irritation of the gums, causing great discomfort to the patient.
It is, in most cases, reversible and there are some measures that can be taken to minimize this adverse effect. The use of desensitizing toothpaste before, during and after whitening treatment, laser therapy and analgesics are some of the successful measures in eradicating tooth sensitivity.
The use of toothpastes with calcium, potassium nitrate and sodium fluoride, as well as topical applications of fluoride, have also proved to be very effective in reducing tooth sensitivity.

Sensitivity can be triggered by multiple factors, such as the pH of the active substance, the time and type of use, the concentration of the bleaching agent, the type of light, dentin exposure due to gum recession, cracks in the tooth enamel and tooth permeability.
It is important to point out that only a fraction of patients present tooth sensitivity after whitening, and those who do present it, must be individually monitored in order to assess the degree of sensitivity for adjustment of the therapeutic indication.
Recommendations after tooth whitening
According to the website Clinical Update Dentsply (2016), the recommendations suggested to patients after tooth whitening are as follows:
• Patient must refrain from ingesting food and beverages with artificial colouring agents during the whitening gel treatment;
• At dentist’s control appointments, check the evolution of the whitening process, analysing the colour of the teeth by comparing them with the colour scale and book dental appointments every 6 months to control oral health.
Usually the main tooth whitening results are noticed after 2 weeks. Some dentists report that the whitening process in the lower arch takes longer, which can be explained by the fact that it is in greater contact with saliva. 
Whitening toothpastes
Manufacturers of oral care products are aware of consumer requirements and demands for whiter tooth colour and have therefore developed a wide selection of toothpastes, containing abrasive ingredients which help to remove and prevent the formation of extrinsic stains.
Mechanical cleaning depends on the application of suitable abrasives, stronger than the stains but weaker than enamel. However, current products continue to show a compromise between cleaning and unwanted tooth abrasion.
Strong abrasive agents are harder than tooth hydroxyapatite and can, not only damage the enamel and exposed dentin, but also the gum tissue while removing stains, especially if strong pressure is applied during brushing.
The use of toothpaste with high abrasive particles can cause abrasion trauma and bleeding gums due to gum inflammation.
The prolonged use of these toothpastes can also lead to an increase in tooth sensitivity, due to excessive wear on tooth enamel resulting in exposure of the dental tubules.
Even in view of these known and proven disadvantages, further studies are still needed to assess the most effective levels of abrasiveness and concentrations to be used in tooth whitening toothpastes.
Conclusion 
In short, there are different ways to whiten teeth, all of them safe and effective, taking into account the individual and individual characteristics of each patient. The Dentist must be familiar with current protocols and decide together with the patient the best therapeutic option.
At the HPA Health Group, the Dental HPA Team provides an excellent service when it comes to smile transformations. All types of clinical procedures can be carried out to achieve a single objective: your well-being.
It is with great satisfaction that I am part of this great team and this transformation project, which helps thousands of people and can also help you. Come visit us and become a part of our big family.