Definitions and Descriptions

According to the laws of physics, colour is defined by three parameters:

Hue: It's the feature that we usually call "colour" itself; for example red hue, blue hue and so on.

Chroma: It corresponds to the colour saturation. Let's imagine to fill a glass with water and to put some red hued pigment into it, drop by drop. The colour of the water gets "redder and redder", up to the point where even adding more colour, the red stays the same. This condindion is called "maximum saturated" colour.

Value: it's more or less the brightness of a colour. For sure it's the most visible feature of an object when we look at it. Small differences of hue or chroma are less noticed than a value difference.

We propose a Wikipedia link for those who want a more detailed description of how the system works:

Munsell's colour system

Stating that teeth are white is saying something very generic that everybody knows to be very unprecise. There are many gradations of "white" in nature and, as a matter of facts, what we consider to be the tooth's colour is in reality a very complex thing.

White tooth colour is the result of the overlapping of more layers:

ENAMEL: This part of the tooth is very lacking of colour, in the sense that if we watch a fragment holding it against a light source, we may notice that it looks more like a ground glass, with almost no coloured features. It's important to underline that enamel is 95% built of a calcium crystal and has very little organic matter in it.

DENTINE: It's the layer below enamel (see anatomy of the tooth) and it's the one that really carries the colour feature. Being mostly formed by an organic substance of proteinic origin, it differs very much from enamel regarding characteristics, and particularly, it tends to aquire pigmentation with ageing and to become darker.

Color scale: In dentistry, the global colour of a tooth is recorded by simply doing a confrontation between the tooth and a given fixed sample. There are many dental colour scales, but the most universally used (even if not the best one) is the "Vita Classic", a system based upon the statistic relevance of some colours in the caucasian race type.

When scheduling for a dental bleaching, the initial colour recording is foundamental to actually predict if that tooth can get whiter or not.

Teeth whitening can be performed at various levels.

TOOTHPASTES AND ABRASIVE PASTES- Many of these products are of common use and freely available in pharmacies and stores. They are based on their abrasive effect. This feature means that the enamel's surface is finely roughened, thus allowing to reflect the light more efficiently: in this way the "value" (see definition) or the tooth's brightness gets dramatically better, however the result is only temporary because scratching the enamel means exposing the enamel itself to food pigmentations coming from the diet (coffee, tea, certain vegetables, smoke etc)

The patient will thus be obliged to use rising quantities of these whitening pastes in order to remove the pigments and regain the tooth's whiteness, extending the damage on the enamel.

It may be observed however that this system does not solve the problem anyway: we explained elsewhere that the tooth's color is mainly delivered by the proteins of the dentine, so it's the dentine that should be eventually whitened, not the enamel.

PEROXIDES- These are substances that release free oxygen. Oxygen has the property of partially denaturating the pigmented proteins, with the result of making them lighter. Of course, since it's the inner dentine proteins that give the color to the tooth, it'll be necessary for the peroxides to reach this layer. the following chapters describe how.

WARNING!! Two absolutely foundamental factors have to be signalled to the patient:

a) Teeth starting from an already very white color, will whiten very little

b) Fixed prosthetics and dental fillings don't whiten at all!

The devitalized tooth often looks darker than living ones. This happens because of the degeneration of proteins inside the dentinal structure that aquire pigmentation. Being this a "dead" tooth, the dentist has a unique occasion for its bleaching: the access to its internal part through the pulpal chamber, the space previously occupied by the pulp that is.

Being able to "see" the dentin from the inner side, it's possible to operate by inserting the peroxides, the substances that produce the bleaching, directly inside the chamber.

This method is highly effective and quite fast. Professional products (not available for free buy) that can be used for the purpouse.

The tooth must absolutely be isolated with rubber dam to protect the soft tissues (the gum) from the exceeding outsldes of the substance, and the dentist must place a safe obturation on the chamber's floor that seals it from the rest of the root canal in the safest way. The risk is that of an infiltration of the substance towards the apex with a possible root reabsorbing process.

With the aim of accelerating the chemical reaction of the belaching, the tooth can be exposed to a warm source or to ultraviolet lights while open, in a dedicated appointment.

It must be said though, that the presence of lights or warm sources only changes the speed of the reaction , not its effectiveness.

Some protocols use very simple appointments where the pulp chamber is simply washed through and fresh bleaching substance is placed. In this way, after a certain number of appointments ranging from 4 to 10 and within 1 to 4 weeks, the result is obtained.

When teeth are vital and do not offer the chance to bleach them from inside the chamber, it is always possible to whiten them from the outside.

The substances used (peroxides) filter through the enamel: as a matter of facts they run along some subtle interstice between enamel crystals made up by a proteic matrix. Through this canal, the substances reach the dentin where, by releasing oxygen they enact their bleachng action.

Practically, the most used method is the domiciliary one in which a kit is given the patient, containing a sort of dental mask that is to hold the gel, plus the tubes of the substance itself.

As an alternative, appointments can be done at the dentists', with or without the use of UV rays to activate the substance.

At this point it's worth recalling that these procedures have the only aim of accelerating the reaction but are not decisive.

Obviously, the substance is not "intelligent" and releases its action on the proteic matrix of the enamel as well: the result is a partial denaturation of this with a rise of the tooth temperature sensitivity and, according to certain studies, also to caries permeability.

For this very reason it should be better to do the whitening process under the supervision of a professional. The dentist choses the most balanced product, surveys the patient's sensitivity, eventually proposing desensitizing treatments, and decides the duration of the treatment.

The duration of the treatment and of the domiciliar protocol are extremely variable and cannot be indicated in a definitive way.