Cavities always have an external beginning, although the internal dental layers tend to decalcify and soften first, it usually seems very intact until in further phases, when by mechanical effects, the external layer breaks and the cavity appears.

Cavities appear as stains on the dental enamel, these stains can be black, grayish or white.

White Stains	Grayish and Black Stains

The cavities' color implicates de lesser or greater velocity at which the destruction of the dental piece is taking place. White cavities progress at a faster pace and black ones at a lower.

When a cavities affects at an enamel level it does not present symptoms, this means that it does not hurt or present sensitivity, since the enamel has no nerves. When a cavity reaches the dentine, located under the dental enamel and with innervations, the patient will complain of temperature (cold/hot), acids and sweets sensitivity.

The patient may also recall a greater food remain accumulation between dental pieces and also may report that while flossing the dental floss tends to shred.

As the cavity process goes deeper, bacteria arrives at the dental pulp (nervous vascular package) causing it to swallow, producing the hurtful acute pulpits, described later on.

During a cavity's exploration using a probe or explorer we can detect the dental tissue's continuity solution or what is the same, the presence of cavities with different magnitudes.

We then can cause, with the help of a probe, the breakage of the superficial layer and produce a cavity, this bares no importance since an easy breakage indicates that there was destruction under it and while treating it all the tissue will be eliminated.

The exploration using a probe also helps in making a differential diagnosis in the case of hipoplastic white stains since when these are pressed no cavity is produced and also because these stains already appear when the dental piece erupts.

White Stains. Cavity beginning

When the cavity is new it will be denominated as PRIMARY CAVITY, if it appears at the side of a filling indicating filtration it is called SECONDARY CAVITY and if it appears under a filling it is called RELAPSING.

The diagnosis is completed with an X-ray study to confirm the presence of decalcificated areas and cavities, if any.

There are other no so common methods to diagnose a cavity, for example: electronic detection, transillumination and colorimetric tests.

There are also, and they will be described later on, tests to quantify the amount of bacteria (streptococcus mutants and lactobacillus acidophilus) present in a patient.