Distal bite in children and adults

Incorrect positioning of the upper and lower jaws with impaired closure of the dentition is a common orthodontic problem, and the most common type of pathological occlusion is the distal occlusion (code K07.20 according to ICD-10).

Epidemiology

According to WHO statistics, among Caucasian patients with occlusion problems, the frequency of skeletal distal occlusion is 38%, and in blacks - no more than 20%. According to other data, the detection of prognathic distal occlusion in the population does not exceed 26%.

At the same time, this type of malocclusion in 80-85% of cases is observed in childhood - during the eruption of milk teeth and their replacement with permanent ones. And only in 15-20% of cases, the distal bite is formed in adults. [1]

Causes of the distal occlusion

Anatomical causes of  malocclusion  in the form of distal occlusion can be associated with:

• with an increase in the size of the upper jaw - macrognathia (gnathos in Greek - jaw);
• with  excessive development of the upper jaw (upper prognosis)  and its forward extension, in which protrusion of the upper frontal teeth is noted;
• with mandibular micrognathia, hypoplasia, microgenia or  underdevelopment of the lower jaw  (which is called mandibula in Latin);
• with the position of the lower jaw deepened into the oral cavity with the correct position of the upper jaw - mandibular retrognathia;
• with the simultaneous retrognation of the lower jaw and prognosis of the upper;
• with a posterior deviation of the dental arch of the lower jaw or the posterior position of its alveolar process - mandibular alveolar retrusion.

Many of the listed defects of the dentition are the result of improper formation of the visceral (facial) skeleton during intrauterine development. In addition, congenital skeletal (jaw) distal and mesial bite (in which, on the contrary, the upper jaw is insufficiently developed, and the lower jaw is pushed forward) has a constitutionally inherited character and can be observed in the genus. [2], [3]

A deep distal bite in a child can be due to:

• bilateral palatine clefts -  congenital nonunions of the palate , as well as the alveolar process of the upper jaw and lip;
• congenital lower micrognathia, which is isolated in only 20% of cases, being a sign of a large number of syndromic disorders with varying degrees of developmental delay, in particular, Marfan, Seckel, Noonan, Apert, Cruson, Pierre Robin syndromes, trisomy 13 ( Patau syndrome ), hemifacial microsomias,  cat cry syndrome , maxillofacial dysostosis ( Tricher Collins syndrome ), etc.  [4], [5]

Also read:

• Anomalies and deformities of the jaws
• Wrong bite in a child

Distal occlusion in adults can form due to maxillofacial injuries or pathological fractures of the jaws and / or their alveolar parts with a history of chronic osteomyelitis or fibrous osteitis, as well as due to degenerative changes in  the temporomandibular joint  (for example, with deforming osteoarthritis)...

Risk factors

The real and possible risk factors for the formation of a distal occlusion include:

• heredity, that is, the presence of this orthodontic pathology in the family history;
• pathologies of pregnancy and various teratogenic effects on the fetus, which increase the likelihood of congenital defects of the facial skull;
• improper artificial feeding in infancy, prolonged use of a pacifier;
• dysphagia (swallowing disorders);
• a child's thumb, tongue, or lip sucking habit;
• an anomaly of the tongue (glossoptosis) or shortening of its frenum;
• improper eruption of milk teeth and violation of its sequence;
• chronic enlargement of the tonsils and adenoids;
• habitual breathing through the mouth;
• dentition changes - early loss of the first permanent molars or incisors;
• abnormal growth of permanent incisors;
• injuries to the facial bones, jaws and teeth;
• weakness of the chewing and orbicular (circular) muscles of the mouth.

Pathogenesis

Orthodontists explain the pathogenesis of the distal occlusion by gene abnormalities or congenital imbalances of the visceral skeleton, which are manifested in the forward shift of the upper jaw (prognathia) or backward displacement (retrognathia) of the lower jaw in such a way that the upper teeth are too advanced anteriorly.

In addition, the mechanism of the formation of jaw prognathia-retrognathia in young children may be due to the above physiological and functional factors. So, in infants, the lower jaw is initially shifted slightly back, and then - with the beginning of the appearance of the first milk teeth - it takes a normal position; bottle feeding does not put the necessary stress on the chewing muscles, and because of this, the lower jaw may remain insufficiently developed with the fixation of mandibular retrognathia. In this case, the situation is aggravated when this is a hereditary constitutional feature of the visceral skull. [6]

As for breathing through the mouth, it affects the position of the tongue in the oral cavity: it cannot perform a supporting function for the upper dental arch, and during the formation of the child's dentition, this leads to lateral narrowing of the upper jaw, its prognosis and subsequent deflection of the upper incisors forward...

Symptoms of the distal occlusion

There are such external and orthodontic symptoms of improper closing of teeth with distal occlusion, such as:

• anterior frontal displacement of the upper jaw;
• expansion of the upper dental arch and shortening of the anterior part of the lower dental arch;
• backward displacement of the lower jaw or inward displacement (retrusion) of the lower incisors;
• overlapping of the lower dental arch by the upper anterior teeth;
• an increase in the interocclusal gap between the upper and lower anterior teeth, which prevents the normal closure of the dentition;
• pressure of the cutting edges of the lower incisors on the mucous membrane of the hard palate.

With deep distal bite, the lower part of the face is shortened, and the teeth of the upper row can almost completely obscure the lower dentition.

Obvious external signs of a prognathic distal occlusion: the facial part of the skull is convex; the chin is slanted and pushed back; there may be a double chin; the lower lip and nasolabial folds are smoothed, and the fold between the chin and the lower lip is deep; the upper lip is shortened, and when smiling, the alveolar process of the upper jaw protrudes outward. Also, in patients with superior prognosis, there may be gaps (three) between the crowns of the upper anterior teeth. [7]

And with a strongly protruding upper jaw, the mouth of the patients is constantly open (due to the impossibility of closing the lips), and the lower lip may be behind the upper incisors.

Forms

The types or types of distal bite identified by specialists depend on the nature of the anomaly: it can be jaw, and with an abnormal position of the upper jaw (prognathia) it is defined as a prognathic distal bite.

There is also a dento-alveolar type of distal occlusion: when there is anterior extension of the maxillary dental arch and / or alveolar process (alveolar prognathia), or the upper incisors are inclined anteriorly. The same type of bite is diagnosed when the mandibular dental arch or the alveolar part of the lower jaw is deflected back, or there is a deviation of the anterior lower teeth into the oral cavity.

In addition, there may be a combined bite - dentoalveolar.

When, when the teeth are closed, the upper incisors overlap the crowns of the lower incisors by more than a third, a deep distal occlusion is determined. And the distal open bite is characterized by the absence of closing of a part of the upper and lower molars and the presence of a large vertical gap between their chewing surfaces. [8]

Complications and consequences

The main negative consequences and complications in the presence of distal occlusion and, especially, in cases of deep or open distal occlusion are manifested:

• Difficulty biting and chewing (and subsequent stomach problems due to insufficient chewing of solid foods)
• difficulty swallowing;
• functional disorder of the temporomandibular joint (with pain when opening the mouth and crunching when chewing);
• trauma to the soft palate with the lower incisors;
• hypertonicity of the masticatory muscle and  bruxism ;
• increased formation of  tartar ;
• increased erasure of the posterior molars and their deterioration;
• problems with articulation and diction.

Diagnostics of the distal occlusion

Diagnostics begins with a visual examination of the patient's teeth and jaws, fixing his complaints and taking anamnesis.

By conducting teleradiography (or computerized 3D cephalometry) and making appropriate measurements, the anatomical parameters of the facial skull and dentition are determined: the height of the face; the size of the nasolabial angle; the ratio of the position of the upper and lower jaw relative to the anterior part of the base of the skull; angles of inclination of the alveolar processes of the jaws, the teeth themselves and their occlusal plane.

Also instrumental diagnostics includes:

• orthopantomogram - panoramic x-ray of the maxillofacial region ;
• computed or magnetic resonance  imaging of the maxillofacial region ;
• study of the tone of the jaw muscles (electromyography).

Differential diagnosis

Differential diagnosis based on cephalometric analysis data should clearly determine the type of malocclusion in order to select the optimal method for its correction.

Treatment of the distal occlusion

To correct the distal occlusion, there are various modifications of orthodontic structures and devices. First of all, with the dental-alvellar type of distal occlusion, braces are installed to correct the position of the teeth and dentition in children (after the replacement of milk teeth with permanent ones), adolescents and adults.

Additionally, in braces that exert pressure on the dentition, an individually manufactured multiloop arch is used for skeletal-type distal occlusion. With its help, you can correct the defects of the dentition, often accompanying prognathies. Braces and a loop are worn constantly and for a long time, and after they are removed, to consolidate the results of correction, removable or stationary restraints are placed on the inner surface of the teeth for some time: orthodontic retention plates or orthodontic splints (retainers).

And to change the abnormal inclination of the frontal teeth of the upper row and stimulate the orbicular muscle, the installation of vestibular plates is practiced for children.

Instead of plates, a trainer for the distal occlusion of the dental-alvellar type is sometimes used, which is a silicone alignment brace-trainer, put on the teeth for their correct positioning. Before orthodontic treatment (since the installation of braces is carried out only for permanent teeth), children with bite problems can be fitted with a pre-orthodontic trainer from the age of six (with the onset of the mixed bite period). [9]

In some cases of distal occlusion of jaw origin during the growth of the visceral skull, it is possible to treat the distal occlusion without surgery. For this, functional orthodontic appliances for distal occlusion can be used:

• bionators (Balters and Janson), consisting of plates and arches, the adjustable force effect of which contributes to an increase in the body and branches of the lower jaw and its anterior displacement;
• functional Frenkel regulator (two modifications), used to correct this violation of occlusion during the active growth of children at the end of the period of eruption of milk teeth and at the beginning of their replacement with permanent ones;
• teeth-supported Herbst and Katz apparatus that stimulate the growth of the lower jaw by correcting the contraction of the orofacial muscles;
• stationary device Forsus for the upper and lower dentition, which allows you to simultaneously move the protruding upper incisors back and pull the lower teeth forward in adolescent patients;
• Semi-rigid Twin-Force correcting device for deep distal occlusion with mandibular retrognation, fixed on both dental arches. Similarly, the use of the Twin Block device - TwinBlock for distal occlusion with mandibular hypoplasia; the design is attached to the dental arches so that the anterior position of the lower jaw is ensured and normalizes the occlusal relationship of the dentition. [10]

Can distal occlusion be corrected with aligners or veneers? In fact, transparent aligners made from the impression of the patient's jaw are modernized aligners, and they can fix the dentition without affecting the alveolar ridge of the upper jaw. Therefore, these dental onlays (worn around the clock, removed before meals) can help reduce the anterior inclination of the upper incisors. [11]

But veneers that improve the appearance of the anterior teeth are not installed on the distal occlusion: this is an aesthetic dentistry procedure that cannot straighten an abnormally located dentition. Their installation can be performed only after orthodontic treatment, for example, to change the shape of the crowns of the anterior teeth in the presence of large interdental spaces.

Surgical treatment, operations

According to foreign clinical statistics, surgical treatment of distal occlusion is carried out in about 5% of patients with a skeletal type of prognathic bite with pronounced maxillofacial defects, ankylosis and degenerative changes in the temporomandibular joint. [12]

In orthognathic surgery, an operation is practiced for distal occlusion, which is aimed at correcting pathological changes in the dentition - prognathia or micrognathia, which are rarely amenable to treatment with braces, plates and other devices to correct occlusion.

Oral and maxillofacial surgeries are performed for cleft lip and palate, osteotomy of the upper jaw - with retrotransposition (backward movement) of its frontal part and fixation in the desired position (non-removable titanium mounts). In adult patients with an open distal occlusion, a compactosteotomy may be performed.

In the presence of mandibular retrognathia, various methods of mandibular osteotomy can be used. [13]

Exercises for distal occlusion

For the normal functioning of the orofacial muscles and temporomandibular joints, it is recommended to do exercises for distal occlusion and other disorders of the dentoalveolar system. Exercises for the chewing, pterygoid, circular and other maxillofacial muscles refer to myofunctional therapy, which helps to increase the efficiency of using orthodontic appliances. [14]

Special myogymnastics for distal occlusion should be done daily - twice for five to ten minutes. Here are some of the main exercises:

• wide opening and closing of the mouth (several repetitions);
• the maximum possible extension of the lower jaw forward;
• forcefully puffing out the cheeks, holding the air for 10 seconds and slowly blowing out (this exercise can be done with water);
• stretching the lips with a tube, and then stretching them (as with a smile);
• abduction of the tongue to the base of the palate (with the mouth closed).

Prevention

With hereditary features of the anatomy of the visceral skull and in children with syndromic anomalies of the jaws, which are congenital and genetically determined, prevention of distal occlusion is impossible.

Experts believe that the main preventive factors for the development of a distal occlusion in a child are his natural breastfeeding (and if artificial, then correctly organized), refusal of a pacifier, weaning of the above habits, etc. It is necessary to treat in time everything that can prevent the child from breathing freely through his nose.

Forecast

With the dental-alveolar type of distal occlusion, the prognosis regarding the results of apparatus orthodontics is much better than with the jaw type, when it is necessary to resort to orthognathic surgery.

In adults, it is very difficult, time-consuming and expensive to correct defects in the dentition, and it is even more difficult to predict the outcome of their correction.