Mesial Bite: Signs, Causes and Treatment
3 min read
A mesial bite (prognathism, or underbite) is an anomaly in which the lower jaw is positioned forward relative to the upper one and the lower incisors overlap the upper ones. It is less common than a distal bite: according to various sources it affects 12–15% of people. But it is the mesial bite that most often requires a comprehensive approach and, in severe cases, the involvement of a surgeon. Here is how to recognise it and what options patients of different ages have.
Signs of a mesial bite
A mesial bite is noticeable even to a non-specialist: the chin protrudes forward, the profile looks "concave", the upper lip appears sunken and the lower lip large. When the teeth close, the lower incisors sit in front of the upper ones (reverse overjet) or the cutting edges meet edge to edge.
Functional signs may include:
- difficulty biting and chewing food;
- speech problems, especially with whistling sounds;
- accelerated wear and overloading of the front teeth;
- pain, clicking and restricted movement in the temporomandibular joint;
- altered facial proportions with a "heavy" lower third.
Why a mesial bite develops
Heredity plays the leading role: excessive growth of the lower jaw or underdevelopment of the upper jaw often runs in families. Other causes include:
- congenital features of jaw development, including after cleft palate;
- bottle feeding with a poorly chosen teat, when the child has to push the lower jaw forward;
- mouth breathing and a low tongue position;
- early loss of upper baby teeth;
- harmful habits such as sucking the upper lip or pushing the jaw forward;
- enlarged tonsils that push the tongue forward.
How the diagnosis is made
A mesial bite can be dentoalveolar (the problem is in the position of the teeth) or skeletal (the problem is in the size or position of the jaws). The treatment plan depends directly on the form, so diagnostics include:
- a clinical examination and functional tests, in which the doctor checks whether the patient can move the lower jaw back into a normal bite;
- a photo protocol of the face and dental arches;
- a 3D scan of the dental arches and model analysis;
- X-ray examinations: a panoramic image, a lateral cephalogram and computed tomography to calculate the position of the jaws.
Treatment at different ages
Children aged 3 to 12
This is the most favourable period: the jaws are growing and growth can be guided. Removable functional appliances, plates with screws to expand the upper jaw, and face masks that stimulate forward growth of the upper jaw are used. At the same time the causes are addressed: nasal breathing is restored, harmful habits are corrected, and a speech therapist is involved if necessary.
Teenagers
During active growth, braces or aligners are used together with intermaxillary elastics. The doctor uses the remaining jaw growth to achieve the correct relationship without surgery.
Adults
If the problem lies in the position of the teeth, a mesial bite is corrected with braces or aligners. Modern aligner systems can handle many cases with reverse incisor overlap. In a pronounced skeletal form, moving the teeth only masks the problem, so combined orthodontic and surgical treatment becomes the best option: the orthodontist prepares the dental arches, the surgeon corrects the position of the jaws, and the orthodontist then completes the work.
Prognosis and retention
When treatment is started in time, chewing and speech function can be restored and the profile normalised. The active stage takes on average from one and a half to three years depending on complexity, after which a retention period necessarily follows: retainers hold the teeth in their new position and prevent the bite from returning to its original state.
A mesial bite is not a life sentence, but it is a case in which it is especially important not to postpone a visit to a specialist. The iOrtho orthodontist in Yerevan will carry out diagnostics and propose a plan that takes into account your age, the form of the anomaly and your expectations.
