Orthodontics is the special branch of dentistry that studies the various abnormalities of the establishment, development and position of the teeth and jaw bones, is being implemented exclusively by practitioners and specialists in orthodontics. Its purpose is to prevent, eliminate or reduce such anomalies maintaining or restoring the jaws and the facial profile in the correct position as possible.

The orthodontic practice consists basically of two types of therapy that often are consequential.

Surgical therapy: is accomplished by extracting those teeth that hinder the alignment and articulation of others or the correct position dentofacial.
Mechanical therapy: this is implemented by constructing different types of apparatus which we subdivide into:

Active devices: work directly with their force when activated (eg devices with screws, strings, springs, etc..)
Equipment expenses: take advantage of the masticatory forces in itself is inactive (eg buccal plate, inclined plane, etc.).

Main components of biomechanical

Strength: is applied to obtain the result diagnosed, it is appropriate dose it properly to avoid causing errors that may be irreparable. When you have the time then it is preferable to apply forces of little intensity (often for reasons of time, unfortunately, the opposite occurs).
Pressure: it is exerted on the oral tissues by the above component (strength), which is therefore closely linked; the result is given by the resorption of the alveolar tissue and consequent opposition bone (displacement of the tooth in the desired direction).
Anchoring: is the resistance to dynamic forces horizontal, affects a good number of teeth as the anchoring elements must always be far superior to the elements under pressure (minimum ratio of 2 to 1 but in practice this hardly occurs ).
Retention: is the resistance to vertical dynamic forces, it relies in particular undercuts, especially those proximal.

The three classes dental

The treatment of facial dysmorphoses has very ancient roots, just think of the attempt to correct the ipermandibulia (skeletal Class III) of the ruling family of the Hapsburgs. But it is only the beginning of the twentieth century in the United States ranks the problem with a critical sense and scientific fact with E. Angle, depending on the relative position of the first permanent molars (upper and lower) which are distinguished malocclusions in three classes.

The dental Class I is the most represented in the northern European population: the upper molar (mesio-vestibular) occludes in the groove between the mesial cusp of the first molar and central lower> upper canine fits from vestibular between canine and mandibular premolar .

Class II dental is the most represented in the Indo-European population where the center of gravity of the body lies ahead, and the jaw grows and develops distal to the skull> therefore the upper molar (mesio-vestibular) fits between the marginal ridges of the second premolar and first molar.

The dental Class III (Habsburg) is found mainly in human groups of Asian origin with different types and associations of overdevelopment and underdevelopment mandibular jaw with varying degrees of growth: the upper molar (mesio-vestibular) closes the gap after distal molar lower.

This is only a clinical classification, but there are billions of possible variations in the world's population.
Components of the orthodontic practice

Orthodontic models: they are developed at least a couple (construction and control) and can be stored in special boxes to represent the different stages in orthodontic treatment for a certain period.
Retainers: are those types of hooks which usually in orthodontics have the task of keeping the plate anchored in the resin.

Taken from wikipedia