WHITENING
COLOR
Color is defined according to the optical laws of physics by means of three parameters:
HUE - It is what we commonly call "color", for example, the red hue, the blue hue, etc.
CHROMA - Let's imagine filling a glass with water and adding some red tint, drop by drop. The color of the water becomes more and more "redder", until it reaches a point where even adding more color, it will remain stable. The color is then said to be "saturated".
VALUE - It is the brightness of the color. It is certainly the most visible factor when we observe an object. Small differences in hue or chroma are less visible than a difference in value.
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To learn more about this topic, we refer to a link on the Munsell Color System
THE COLOR OF THE TOOTH
To say that your teeth are white is to say something generic, which everyone knows is rather inaccurate. There are various shades of "white" in nature, and in fact, what we consider to be the color of the tooth is actually something very complex.
The white color of the tooth is the result of overlapping several layers:
ENAMEL - This part of the tooth contains very little color, in the sense that if we observe a fragment of enamel against the light, it has a frosted glass appearance, almost devoid of colored characteristics. It is important to underline that 95% of the enamel is made up of a calcium crystal and contains very little organic substance.
DENTIN - It is the layer underneath the enamel (see tooth anatomy) and it is the one that actually contains the color. Being largely made up of organic matter of a protein nature, it has very different characteristics from enamel: in particular, with advancing age, dentin tends to acquire pigment and become darker.
Shade scale: In dentistry, the shade is detected by directly comparing the tooth with a shade guide made up of sample teeth. There are many, but the most used scale (although not necessarily the best) is the so-called "Vita Classic", which is a system based on the statistical significance of the samples in the Caucasian population.
In whitening, the precise detection of the initial color is essential to understand if that given tooth will be able to whiten or not.
WHITENING
Tooth whitening can be done at various levels.
TOOTHPASTERS AND ABRASIVE PASTES - Many of these products are commonly used and can be purchased freely in pharmacies. They are based on the fact that they contain abrasives. The effect of abrasion is to roughen the surface of the enamel, making it more able to reflect light: in this way, the "value" (see) or brightness of the tooth increases dramatically, but the effect is temporary, because scratching the enamel, also makes it more dirty from the pigmentations coming from the diet (coffee, tea, certain vegetables, smoke etc.)
The patient will then be forced to use more and more of these pastes to whiten again and remove the surface pigments, continuing to ruin the enamel.
Finally, it should be noted that however, this system does not solve the central issue: we have said that the color of the tooth is mainly given by the proteins of the dentin, therefore it is the dentin that should be whitened, not the enamel.
PEROXIDES - These are substances that release free oxygen. Oxygen has the property of partially denaturing the pigment proteins, with the result of making them lighter in color. Of course, since it is the internal proteins of the dentin that give the tooth its color, the peroxide must be able to reach this layer. In the following two titles, it describes how.
ATTENTION !! Patients must absolutely be reminded of two important factors:
a) Teeth that are very white from the outset will whiten very little
b) Some teeth, due to their nature and composition, tend to whiten less
c) Fixed prostheses and fillings DO NOT whiten at all!
ENDODONTIC WHITENING
The devitalized tooth is often darker in color than the vital teeth. This happens due to the degeneration of proteins inside the dentinal structure that acquire pigmentation. Since the tooth is "dead", the dentist has a unique opportunity to be able to whiten it: access to the inside of it, through the pulp chamber, ie the space that was occupied by the pulp.
Being able to "see" the dentin from the inside, it is possible to operate by inserting the substances (peroxides) that operate the whitening directly into the chamber.
This method is most effective and relatively quick. There are professional products (not available on the market) that can be placed in the pulp chamber to carry out their activity.
The tooth must absolutely be isolated with the dam to protect the soft tissues (gingiva) from substance leaks, and also the dentist must place a filling at the base of the chamber that separates and seals it. in an absolutely safe way from the entrance of the canals: the risk is the infiltration of the substance towards the apex with a possible reabsorption of the root.
In order to accelerate the chemical reaction, the peroxide can be activated with a heat source or a special ultraviolet light, with the tooth open during a specific dental session.
However, it must be said that the presence of heat or light sources only affects the speed of whitening, not its effectiveness, and is not essential for its success.
Some protocols simply provide for short sessions at the dentist to wash the pulp chamber and change the whitener: in this way, with a number of sessions ranging from 4 to 10, and within 1 - 4 weeks, the result can be obtained.
EXTERNAL WHITENING
When the teeth are vital and do not have the possibility of accessing the pulp chamber from the inside, it is still possible to whiten them from the outside.
The substances used (peroxides) filter through the enamel: in fact they run through the very thin interstices present between the crystals of the enamel and which are made up of a protein matrix. Through this "channel", they reach the dentin, where, releasing oxygen, they exert their whitening action.
Practically, the most used system is the chairside one, where the whitening substance (gel peroxide) is placed on the enamel of the teeth, after having protected the gums with a special barrier. A special UV lamp activates the substance releasing its whitening power. It is possible to perform two types of whitening in the studio:
a) Short or "test" whitening - Usually applied in the last 15 minutes of a normal hygiene session, applying a low concentration gel. With a reduced expense for the patient, useful indications can be drawn to understand if that set of teeth has a good ability to whiten or not. Depending on the effect, you can decide to switch to a complete whitening.
b) Complete whitening - Use the same procedure as the test one, only using a high concentration whitening gel kit for a longer time (about 45 minutes). The effect is obviously greater than in the short session and is applied when it is reasonably sure that the teeth give a good response.
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Alternatively, there is the possibility of practicing "home" whitening, where the patient is given a kit that includes a sort of tray or mask to be applied to the teeth and which will contain the gel, in addition to the tubes of the substance itself. Not acting under UV activation, the substance acts slower and above all not under the direct control of the dentist.
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Of course, the chemical substance is not "intelligent", so it also exerts its action on the protein matrix of the enamel: the result is a partial denaturation of the enamel as well, with a certain increase in the sensitivity of the tooth to temperature and, according to some studies, also of the permeability to caries, even if modern buffered products offer sufficient guarantees from this point of view.
For these reasons, whitening should be done under close professional supervision. The dentist proposes the most balanced product, monitors the patient's sensitivity, possibly proposing desensitizing treatments, and decides the right duration of treatment.