ANTERO-POSTERIOR PLANE (SAGITTAL)

FIRST DENTAL CLASS

The mesio-vestibular cusp of the 1st upper molaroccludes in the vestibular sulcus of the 1st lower molar, while the cusp of the upper canineoccludes between the distal side of the canineand the mesial side of the 1st lower premolar. It is referred to as correct occlusion or normo-occlusion, since the relationships that are established between the various dental elements in this type of occlusion allow an effective and efficient function with less energy expenditure. Obviously, as mentioned in the introduction, the remaining factors that influence the whole system must also be in balance. Precisely for this reason, the correct occlusion is given by a concert of small and large balances that derive from both contiguous areas and from near or distant areas. The same class 1 molar and canine occlusion can present position defects of some dental elements, creating what are called crowding, that is, partial overlapping of some dental crowns which are caused, for example, by inadequate shape relationship between the reciprocal elements contiguous or antagonistic. In addition, the balance of class 1 involves adequate muscle activity, collaborates in achieving and / or maintaining postural balance

SECOND DENTAL CLASS, FIRST DIVISION AND SECOND DIVISION

Class 2 has similar molar and canine ratios, with differences related to the pro-inclinations or endo-inclinations of the frontal groups.

These different positions of the front elements are attributable to various factors. In particular, we can mention neuromuscular imbalance both in the tongue and in the lips. Imbalance of the lips can occur through a muscle hypotone (for divisions 1), or a muscle hypertone capable of endoinclining the elements of the frontal group (division 2). The vestibular sulcus of the first lower molaris distal to the mesiovestibular cusp of the first lower molar. The superior canineis advanced compared to the inferior canine. The etiopathogenesis of classes 2 can be due to numerous factors. Genetics, trauma from gestation or childbirth that affect the conformation of the skull, parafunctions, facial skull development in childhood, oral respiration, early loss of dental elements, neuromuscular disorders, postural attitudes, more complex syndromes etc. Class 2 can be the result of a dental mal-position, but also of a skeletal mal-position. From the point of view of the skeleton, we can find ourselves in front of a more advanced maxilla with a correct sized jaw, conversely we could have a correct sized maxilla and a smaller or rear positioned jaw, or we could have the sum of the 2 factors. Therapies in different situations are different and require levels of attention appropriate to the severity of the case. From a functional and postural point of view, class 2 negatively affects the neuro-muscular and articular system. When we have a rear-positioned jaw for example, this has impact on the TMJ causing dysfunctions that over time can lead to imbalances that activate more complex disorders, especially when associated with other levels of imbalances or parafunctions (for example, clenching or bruxism). Even the anterior wall that often occurs in division 2, due to the deep bite between the upper and lower frontal group, causes a really significant functional limitation.

THIRD DENTAL CLASS

The third dental class sees the vestibular sulcus of the first lower molarin a mesial position with respect to the mesiovestibular cusp of the first upper molar. The cusp of the upper canine is positioned distally with respect to the cusp of the canine at more than 3 mm.

An occlusion is defined as incorrect, the etiopathogenesis of which has a strongly genetic component but it can also be caused by several other factors such as: trauma from gestation or childbirth, parafunctions, (defined as fake third classes), due for example to factors that require the jaw to take a more advanced position to function better, neuromuscular disorders, postural positions, more complex syndromes etc.

FRONT PLANE

NORMAL BITE

The correct closure of the dental arches provides for the coverage of the upper arch with respect to the lower of 2 +/- 2 mm.

This closure allows adequate protrusion and lateral movements during the different functions of the mouth

DEEP BITE

When the dental elements close excessively between themselves, leading to an excessive coverage of the upper arch compared to the lower one, we are faced with a deep bite. As already mentioned, it functionally causes a blockage of the normal function of the mouth, often causing muscle and temporo-mandibular dysfunction. The deep bite can be anterior or posterior, unilateral or bilateral.

OPEN BITE

The open bite is characterized by an opening of the space between the teeth of the two arches, which does not allow adequate support and therefore correct occlusion. It is caused by various factors: neuro-muscular dysfunctions, oral respiration, atypical swallowing, dental mal-position, mandibular mal-position.

TRANSVERSE PLANE

On the transverse plane apart from the shape of the arches ( which must be appropriate to the age, the dental  shape  of the subject, as well as having an ovoid shape) there is the aspect of the relationship of the lateral closure of the two arches. When the upper arch is proportionally smaller than the lower arch, or vice versa, we may find ourselves in front of an incoordination of the two arches, so that  cross-chewing  may occur which can be unilateral or bilateral.

UNILATERAL CROSS BITE

Unilateral cross-bite occurs with a more or less significant deviation of the lower median from the body median. The etiopathogenesis can be linked to several factors: genetic, skeletal, syndromic, from trauma from gestation or childbirth, from parafunction, from ogival palate, from oral respiration, from dental pre-contact with sliding towards a more comfortable position. Unilateral cross bite, if not intercepted early, can lead to a later functional deviation in developmental age becoming structured in adulthood as a facial asymmetry.  Early treatment is highly necessary.

BILATERAL CROSS BITE

Bilateral cross bite has the same genesis and characteristics as the unilateral cross bite, with 2 characteristics that distinguish it:

1. cross bite is present both on the right and on the left;
2. it develops a symmetry that makes it, although more serious than the unilateral cross-bite in terms of proportional discrepancy between the two arches, less serious on the asymmetric front, since being present on both sides, most of the time it does not cause facial asymmetry.

Cross-bites are also defined by functionalists as mouth scoliosis. From a functional point of view, they have a negative impact on almost all the functions of the mouth, as well as on the postural level. They cause conditioning, due to the asymmetric function of the muscles, which affects the descending muscle chains.