The orthodontics study consists of analysing the patient’s face directly and using photographs, analysing their teeth directly and using plaster models, and analysing X-rays.
We analyse different characteristics of their teeth, and the relationship between the different teeth.
Here we study the relationship between the upper and lower teeth on the anterior-posterior line of the mouth. We consider the relationship between the canines and the first superior molars with their lower counterparts while the teeth are closed together. In the case of the canines we use Angle’s Classification:
- Class I is the normal relationship we work to achieve with orthodontics. The cusp of the upper canine meets the rear edge of the lower canine.
- Class II, the cusp of the upper canine is in front of this position. This often occurs when the jaw is retracted.
- Class III, the cusp of the upper canine is behind this position. This often occurs when the jaw is protruding.
In the normal position, when the teeth are closed, the upper incisors cover 1/3 of the lower incisors.
This is when the upper incisors cover more than 1/3 of the lower incisors. When a bite is 100% closed, the cusp of the lower incisors bites the gum of the lower incisors. The lips have very strong muscles.
Here there is no occlusion between the incisors, i.e. when the patient closes their teeth the upper incisors do not meet the lower incisors. Something is preventing them from meeting, usually either the tongue or the lip coming between them (a lingual or labial habit), or because the patient sucks a finger, almost always their thumb.
Length of the dental arch
This measurement is taken from the front of the first molar to the front of the same molar on the other side. If the length is short, the teeth are either crowded or very small. Using different mechanisms, such as bringing the incisors forward or moving the molars backwards, broadening the arch or extracting one or more teeth, we obtain more space and can align the teeth without crowding by means of orthodontic treatment.
The upper teeth must be visible. Crossbite can be:
The upper anterior teeth close inside those on the lower jaw. This occurs in the case of very prominent jaws, when the jaw protrudes in relation to the upper maxilla.
The back teeth, i.e. premolars or molars or both, close inside the lower teeth due to a narrow palate. This can occur on one or both sides.
Other characteristics of the teeth
Tooth shape and size
We look to see if the size is normal in relation to the size of the bones. If they are small, the teeth will be separated, with diastemata, or spaces. If they are large, they will be crowded. Sometimes we find small and conical individual teeth.
Number of teeth
Some teeth may be missing, perhaps due to having remained in the bone, to having been extracted, or due to not having formed (agenesis). There may also be extra teeth (supernumerary teeth).
It is important to study the thickness of the gum; the greater the thickness the more we can move the teeth. If the gum is thin, it may recede and leave part of the root uncovered.
To proceed with orthodontics in adults, their gums must be healthy, without gingivitis, bleeding or periodontal disease, as we would otherwise experience problems with exposed roots and even tooth loss.
In the orthodontics study, as well as analysing the teeth, we must also analyse the face and X-ray.