Jaw position abnormalities
The various deviations of all three relationships are listed below.
In the forward-backward sense, the upper jaw can be positioned correctly with respect to the lower jaw, too far forward or too far back. These relationships have the following names according to the Angle classification (Angle was the orthodontist who first described this classification at the time).
- Angle class I. Hereby the forward position of the upper jaw relative to the lower jaw is correct (see image below).
- Angle class II. In this case, the lower jaw is too far back relative to the upper jaw. This typing says nothing about which jaw is wrong. It only says something about the relationship between both jaws. With the Angle class II, a distinction is made between class II-1 (where the upper front is tilted forward) and class II-2 (although the lower jaw is too far back compared to the upper jaw, but two or more more upper front elements tilted back) (see image below).
- Angle class III. The lower jaw is too far forward than the upper jaw. This characterization also says nothing about which jaw is wrong. It only says something about the relationship between both jaws (see image below).
In the transversal relationship you look at the teeth and molars from the front. The middle of the upper teeth must be directly above the middle of the lower teeth. We call this the median line. When these centers are not directly above each other, you speak of a median line shift. The shift itself does not indicate in which jaw the deviation is located. That can be both the upper and lower jaw.
It is also possible that the upper jaw is too narrow in relation to the lower jaw. Then the molars of the upper jaw do not fall well on the molars of the lower jaw. Normally the vestibular nodules of the above (pre) molars fall outside the vestibular nodules of the below (pre) molars. When the vestibular nodules of the upper (pre) molars fall into the fissures of the lower (pre) molars, we speak of a cross bite (see images below).
When you close your mouth, the edges of the lower teeth (incisal edges) touch the inside of the upper teeth. The upper teeth fall slightly over the lower teeth. This is called the depth of the bite. This is normally 2 to 3 mm.
- When the lower teeth fall deep behind the upper teeth, this is called a deep bite.
- When the bite is so deep that the lower teeth touch the palate, it is a palate bite.
- When someone puts the molars together and the upper teeth don't fall over the lower teeth at all, this is called an open bite (see images below).
Dental position and dental position abnormalities
Teeth are normally right next to each other in the jaw and collapse correctly when chewed. This falling together is called occlusion (see image below). Teeth can have a different position in three ways:
- On an individual level. For example, a tooth is too far forward or is rotated about its axis or has not broken through far enough. These are all kinds of dental position abnormalities that have a separate name.
- At group level (intramaxillary). For example, the elements in one jaw are too far apart or on top of each other.
- At the level between the upper and lower jaw (intermaxillary). For example, the upper molar is too far forward relative to the lower molar. The occlusion is then incorrect. Also choosing can scissor each other instead of coming together.
Combinations of the foregoing are also possible. If an upper premolar is not broken enough, it will not hit the lower premolar either. There is then infraoclusion of the relevant upper premolar and at the same time there is an open bite between upper and lower premolar.
Individual dental position abnormalities
The names for dental position abnormalities at individual level are numerous. We explain a number of them:
- Eversion: The element is tipped to the outside. Another name for this stand deviation is labio version or protrusion.
- Inversion: The element is tipped inwards. Another name for this stand deviation is linguo version or retrusion.
- Kipping: The element is tilted to mesial or distal (see image below).
- Infrastructure or intrusion: The element did not break through (enough).
- Supraposition or extrusion: the element has broken too far (see image below).
- Ecto stem: the element is located outside the dental arch.
- Endostema: the element is inside the dental arch (see image below).
Intramaxillary tooth position abnormalities
There are two options for stand deviations at group level:
- Lack of space or crowding: the elements slide over each other (see image below);
- Space surplus or spacing: the approximate sides of the elements do not touch each other. There is space in between (see image below).
Intermaxillary tooth position abnormalities
Numerous stand deviations are possible at the level between the upper and lower jaw. These can be subdivided into forward-backward (sagittal), sideways (transversal) and vertical.
- Neutro-occlusion is the right occlusion. Hereby the mesiobuccal nodule of the first upper molar occludes at the buccal fissure of the first lower molar. The lower incisions then bite their incisal edge close to the palatal plane of the upper incisors. In ideal teeth, the front elements will overlap each other approximately 2 mm in the horizontal direction. We call this a horizontal over-bite or over-jet of 2 mm. The vertical overlap, called the vertical overbite or overbite, is also approximately 2 mm in the ideal situation.
- Disto-occlusion: when the mesiobuccal lump of the first upper molar is too far forward with respect to the first lower molar. In this case, the upper front elements do not touch the lower incisions, but stand in front of them. The horizontal overbite is too large.
- Mesio-occlusion: when the mesiobuccal lump of the first upper molar is too far back compared to the first lower molar. With regard to the incisions, the upper incisions are in this case after the lower incisions. Here one speaks of a reverse overbite or negative overjet (see image below).
Normally the buccal nodules of the upper molars and premolars and also the incisal edges of the upper front fall over those of the lower jaw. The median lines coincide.
- When the first upper molar is too far in, the mesiobuccal nodule falls into the central fossa. This is called cross bite.
- When the first upper molar is too far out, the palatal plane of the first upper molar falls against the buccal plane of the first lower molar. In that case one speaks of scissors bite (see image below).
When someone is close, all elements must be viewed vertically in occlusion. Extensive research has been done on contact points (occlusal contacts) in an ideal occlusion. For each nodule, for example, it is described which contacts he must have with the antagonist (s).