Dental occlusion is the way the upper teeth “mesh” with the lower teeth. We can say that it is all the contacts between the opposing teeth. These contacts are called “intercuspal contacts” because the chewing surface of each tooth is composed of furrows and cusps, a kind of protuberance found at the top.
“Normal” occlusion refers to the position of “maximum intercuspidia”, which is the position where the cusps of the teeth prevent further closing of the teeth. This position is stealthy in natural conditions: it is found especially for a short time at each salivary swallowing (estimated at 1 per minute).
In the position of maximum intercuspidy, the lower teeth are ideally covered by those of the top on the third or quarter of their height. The molars and premolars, for their part, pile up.
This position constitutes the reference occlusal position, but it should not be confused with the “centered relation”which constitutes the reference articular position. The latter is important because it allows to have a reference mandibular position independent of the teeth (they can indeed fall with age). Unfortunately, this reference is controversial, in part because it relies more on clinical experience than on scientific arguments, tears and many schools of dentistry . It does not always correspond exactly with the reference occlusal position.
Angle classification of occlusion
Although dating from the nineteenth century, the Angle classification that bears the name of its designer is still used by orthodontists. There are 3 different classes of occlusion cases:
– Class 1, which is the normal situation. The lower teeth are well offset, behind those at the top, a half-cusp.
– Class 2, which is an abnormal situation. The lower teeth are too far back, a complete cusp.
– Class 2, which is another abnormal situation. The bottom teeth are too advanced compared to the top ones. This usually induces a prognathia and an inverted occlusion.
This classification is always useful, but it has the drawback of not taking into account the occlusion defects in the vertical direction and the lateral direction.
There are several types of malocclusions depending on the direction you are considering (vertical or front to back, for example).
Incisal supraclusis. The upper incisors cover the lower incisors too much.
Incisal infraclusion. The upper incisors do not cover enough of the lower incisors. If it is too marked, there is a gap.
Molar supraclusis. The molars are too out.
Molar infarction. The molars do not touch each other.
Hiatus. The upper incisors are too far forward of the lower incisors.
Cross occlusion. The lower teeth cover the upper ones.
Risk factors for malocclusion
Extractions (edentations) wild or / and uncompensated. The loss of a tooth, extracted by a dentist or not, not replaced, causes very annoying disturbances on the entire dental system. Its absence will cause a real imbalance of forces and will gradually disturb the occlusion. Thus, a tooth that loses its antagonist will seek the occlusal contact and, destabilized, will evolve freely in the space that is now offered. We talk about égression. This is one of the reasons why dentists insist on removing wisdom teeth in pairs. A tooth that loses its distal tooth will also migrate and bow to this free space. These new conformations are responsible for malocclusions and loosening of teeth.
Atypical salivary swallowing. In this abnormal type of swallowing, the tongue interposes between the dental arches. This interposition prevents contact between the opposing teeth and therefore does not cause any proprioceptive stimulation necessary for the occlusal balance. It induces an insidious migration of teeth.
Bruxism . Bruxism refers to the creaking or clenching of teeth outside the periods of chewing or swallowing. Such a condition affects both children and adults at night and day. But it is the night that causes the most problems, because the absence of any control increases the risk of violent shocks and significant dental friction. Premature wear of the teeth will progressively disturb the occlusion.
Extractions of wisdom teeth, damaged teeth, and dental surgeries are also additional risk factors.
The consequences of malocclusions
Malocclusions are likely, in the long term, to have different consequences on health:
– A deterioration of oral health
– The loosening of one or more teeth
– The imbalance of the posture (position of the hips, walking, position of the facial bones)
– The dysfunction of the temporomandibular joint (pain, crunches)
– Various pains (headaches, migraines, postural pains …)
– Snoring or sleep apnea.
– A deterioration of the general state.
– disturbed sleep.