Malocclusion, occlusal disease, or a poor bite, refers to situations in which the upper and lower teeth, or jaw, are misaligned and come together in ways that can damage or destroy teeth. Any deviation from normal occlusion is considered a malocclusion.
The malocclusion occurs when the teeth and jaws are misaligned in the habitual bite. Though most people have a slight degree of malocclusion and do not require treatment, this condition can cause health issues in the temporomandibular joint, teeth, jaw muscle, and gums. Malocclusions are normally categorized with Angle’s classification method, set up by Edward Angle, a prominent orthodontist of the late 19th and early 20th centuries. The classifications are based on the position of the maxillary first molar in relation to the rest of the occlusion.
OCCLUSION AND DENTAL DEVELOPMENT
In dentistry, your occlusion basically refers to how your teeth come together. Occlusion is defined as the contact between the maxillary and mandibular teeth in any functional position. It is more than just your “bite” as you can bite in different ways depending on whether you are chewing or attempting to take a bite out of something. You also bring your teeth together when you swallow and may bring them together in quite different ways when you sleep and are not consciously guiding them one way or another. In a proper occlusion, the cusps of the teeth of the upper jaw line up with the groves of the teeth of the lower jaw and vice versa. In other words points of teeth in lower jaw meet depressions of teeth in the upper jaw in a proper occlusion.
When teeth erupt into the oral cavity, a new set of factors influence tooth position.
1. Genetic factors.
Teeth can vary in size. Examples are microdontia (very small teeth) and macrodontia (very large teeth). The shape of individual teeth can vary (such as third molars and the upper lateral incisors.) They can vary when and where they erupt, or they may not erupt at all (impaction) such as the canines. Teeth can be congenitally missing (partial or complete anodontia), or there can be extra (supernumerary) teeth. The skeletal support (maxilla/mandible) and how they are related to each other can vary considerably from the norm.
2. Environmental factors.
Habits can have an effect on the occlusion and development and position of both upper and lower jaws. Breathing through the mouth, thumb sucking, poor swallowing patterns all have an influence on the occlusion.
3. Muscular pressure.
Once the teeth erupt into the oral cavity, the position of teeth is affected by other teeth, both in the same dental arch and by teeth in the opposing dental arch.
Teeth are affected by muscular pressure on the facial side (by cheeks/lips) and on the lingual side (by the tongue). Once we have identified the possible environmental factors influencing the occlusion, we can make sure they are eliminated and use the muscular pressure to our advantage to establish a more natural occlusion and dental and skeletal form.
EVALUATING DENTAL OCCLUSION
The occlusion is evaluated in the three traditional planes of space as well as arch perimeter and alignment and facial proportions. It is also of utmost importance to consider the esthetics evaluated in these three planes of space:
The overjet measures the horizontal (antero-posterior) discrepancy existing between the upper and lower teeth. It may be characterized by the upper teeth being too advanced in relation with the lower teeth or the lower teeth too far back in relation to the upper teeth. We must also consider the fact that this discrepancy might also be caused by a skeletal discrepancy. The teeth may be properly positioned in relation to their jaws; however, the upper jaw might be too far forward or the lower jaw too far back.
The overbite measures the vertical discrepancy existing between the upper and lower teeth. It is the extension of the upper incisor teeth over the lower ones vertically when the opposing posterior teeth are in contact. Normal overbite is between 2-3 mm (or approximately 20–30% of the height of the mandibular incisors) and is commonly expressed as a percentage.
This is a lateral measurement of the dental arches and jaws. It is the measurement that allows us to determine whether the width of the jaws is sufficiently developed to permit a proper occlusion. It is especially important when considering facial esthetics.
However, Angle’s classification of malocclusion is by far the most commonly used for the molars and incisors and can be generally descriptive for categorizing of malocclusion. A sagittal evaluation of the dentition focuses on the molar Angle classification and the amount of overjet.
Angle’s molar classification is based on the relationship of the first molars as follows:
Class I - Ideal Occlusion
An Ideal Occlusion is the relationship existing when all the teeth are perfectly placed in the arches of jaws and have a normal anatomic relationship to each other. When the teeth are brought into contact, the cusp-fossa relationship is considered the most perfect anatomic relationship that can be attained.
An ideal occlusion is that which shows a coincident mid-line, there is no crowding, no overlap, no rotations or spacing of teeth, there is correct crown angulations and inclination, the molar relationship is Class I, has an over-jet of about 2-4mm, Class I canine relationship. A normal occlusion is one which shows some deviation from that of the ideal but is aesthetically acceptable and functionally stable for the individual.
A Class II malocclusion is one whereby the upper front teeth are protruding over the lower teeth. In other words we observe an excessive horizontal (overjet) discrepancy.
The Class II malocclusion may present itself in many fashions:
- Upper front teeth may be too advanced;
- Lower front teeth may be too far back;
- Upper jaw may be too advanced;
- Lower jaw may be too far back.
In conclusion, a Class II malocclusion may be characterized as a dental problem or a skeletal one or a combination of both.
Very often a Class II malocclusion will manifest itself with an exaggerated overbite (an excessive vertical dimension). The lower teeth might bite into the palate instead of onto the upper teeth.
Two subdivisions in Class II
The Class II malocclusion is separated into 2 subdivisions. The influences of the surrounding musculature are responsible for the Class II malocclusion in taking on different appearances.
Class II Division 1
A Class II Division 1 malocclusion is commonly due to a lower jaw positioned too far back. As mentioned previously, the influence of the soft tissues (lips, tongue and cheeks) play an important role in creating both subdivisions. In a Class II division 1, the lips are typically incompetent (very loose, flaccid) creating the prominence the upper teeth. More commonly, the lower lip functions by being drawn up behind the upper teeth and the lower teeth thereby pushing the upper teeth forward and pushing back the lower teeth. This results in the dental discrepancy becoming more severe than the underlying skeletal pattern.
Class II Division II
As with the Class II Division I, the lower jaw positioned too far back. However, the influence of the soft tissues (lips, tongue and cheeks) is different. Because of active muscular lips and cheeks, the teeth take on a different look. The upper teeth are inclined lingual. Depending on the height of the lip line and the length of the teeth, we can observe either all four incisors tipped backward or only the two central incisors. In most cases the overbite is excessive with the upper incisors touching the lower gum, and the lower incisors biting into the palate.
An excessive overbite can be the cause of wearing of the gums and then the bone leading to severe periodontal problems. These symptoms can occur at any age.
An Angle Class III malocclusion means that the mandibular first molar is positioned anteriorly in relation to the maxillary first molar. Clinically we observe that the lower teeth are too far forward, the lower teeth lie in front of the upper ones and the molar bite is displaced forward.
The diagnosis of such a malocclusion is very important. We need to distinguish if the malocclusion is dental or skeletal.
Dental Class III
The lower teeth are too forward in relation to the upper teeth or the upper teeth or too far back in relation to the lower teeth. In these cases, most often the correction may be performed with orthodontics only.
Skeletal Class III
The Class III malocclusion can also be caused by the jaws not being in the proper positions. We may experience a lack of growth of the upper jaw or an exaggerated growth of the lower jaw. In both situations, the lower teeth will close in front of the upper teeth.
However, there are three main treatment options for skeletal Class III malocclusion:
- growth modification.
- dentoalveolar compensation (orthodontic camouflage).
- orthognathic surgery.
Growth modification should be commenced before the pubertal growth spurt, after this spurt, only the latter two options are possible. In such cases, however, how should clinicians determine whether or not patients are suitable for surgery?
The upper and lower front teeth do no overlap when the back teeth are together. Most often an open bite is caused by thumb sucking. The shape of the opening between the upper and lower front teeth may match the shape of the child's finger or thumb. This obviously interferes with the child's ability to bite into food, and will cause problems with digestion. Poor tongue posture can also be a cause of an open bite. The tongue should not be placed between the front teeth during swallowing and at rest.
An open bite has many adverse affects. First, and most prominently, the patient's smile is adversely affected. Often this results in loss of self esteem. The patient could also develop a lisp which, though cute when he is a child, is not so attractive in later years. It can cause permanent damage in the form of distorted bone growth. And obviously, this problem interferes with the child's ability to bite into food and might cause problems with digestion.
Orthodontic Cross Bites and Palatal Constriction
Cross bites are a reverse position of one or more teeth. A cross bite can be due to either the teeth themselves being reversed in position, or more commonly, the upper jaw and palate are constricted to the extent that the upper teeth do not match the lower teeth on one or both sides. The upper teeth should be to the outside of the lower teeth on both sides of the mouth.
Cross bites are usually caused by a constricted palate. A constricted palate, which causes the teeth to be in crossbite is usually genetic in nature, and can be traced to one side of the family. However, sometimes the unusual eruption of the teeth themselves or a myofunctional problem such as severe tongue thrusting, poor breathing habits (such as breathing mostly through the mouth) or thumb sucking can functionally constricts the palate and deforms the upper jaw. In any case, the result is the same and it is not self-correcting.
When there is a crossbite of a single tooth or in some cases a couple of teeth, this is called a dental cross bite as opposed to a skeletal cross bite. Most often it occurs in the anterior region of the mouth and due to a lack of space.