ANATOMY OF THE MOUTH
THE TEETH
The human mouth has three distinct dentitions: the deciduous one (milk teeth), the mixed one (during replacement), and the permanent one (of the adult). The deciduous dentition is made up of 20 teeth which, normally, appear from the sixth month of age of the child, and complete the eruption around the second year of age.
A full milk teeth set consists of:
2 sup. + 2 inf. central incisors
2 sup. + 2 inf. lateral incisors
2 sup. + 2 inf. canines
4 sup. + 4 inf. milk molars or molars
From the age of 6, a long period begins during which the child completes a total replacement of the milk teeth and acquires a certain number of additional teeth. At the end of the replacement, around the age of 12, the permanent dentition will be composed of 28 teeth. A further 4 teeth (wisdom teeth) appear (but not always) by the age of 18, however their presence is not at all obvious. When they are present, the total number of teeth therefore rises to 32.
A complete permanent dentition consists of:
2 sup. + 2 inf. central incisors (instead of deciduous homologs)
2 sup. + 2 inf. lateral incisors instead of deciduous homologs)
2 sup. + 2 inf. canines instead of deciduous homologues)
4 sup. + 4 inf. premolars (instead of molars)
6 sup. + 6 inf. molars (additional, including wisdom teeth)
THE TOOTH
The human tooth is made up of two anatomical parts, of which only one is visible. The Crown, which is the portion that emerges from the gum and that we can see by looking into the mouth, and the Root, which is the invisible part, submerged under the gum, and linked to the bone.
The teeth differ in shape and size, but they all consist of 4 structures. We describe them from the inside out:
a) PULP
It is also referred to as the "nerve", and forms the innermost part of the tooth. It is a vital tissue that contains blood vessels, nerves and cells of various types. It is the only portion of the tooth that has a true metabolism, and it is the one that, at times, "hurts" if the tooth is attacked by caries.
b) DENTINE
It is the envelope that encloses the pulp in all its length, from the crown to the root of the tooth. It is a largely calcified structure, and is crossed by tubules that radiate outwards from the pulp. Inside the tubules, there are cellular extensions that allow it to partially change its structure. In particular, it is able to create defensive calcifications that tend to protect the pulp from external stimuli.
c) ENAMEL
The hardest part of the tooth (and of our whole body) is actually a crystalline shell, a kind of hood that has the function of withstanding the wear and tear of chewing. It covers the tooth only up to its collar, that is, it constitutes its crown, and is therefore the only visible part, interrupting itself at the height of the gum.
d) ROOT CEMENT
It is the equivalent of the enamel for the non visible part of the tooth, the root. It is a thin layer that covers root dentin, but unlike enamel, it is much less hard. It is the portion of the tooth that is uncovered when the gum and bone withdraw, elongating the collar of the tooth. It acts as an interface with the bone.
