Malocclusion refers to a condition where the teeth do not align properly when the mouth is closed. This misalignment, often called a “bad bite,” can involve crooked, crowded, or improperly positioned teeth. While many individuals have some degree of malocclusion, its severity can vary, sometimes leading to various oral health issues if left unaddressed.
What Defines a Malocclusion
A proper bite, or ideal occlusion, is characterized by a harmonious alignment of the upper and lower jaws and teeth. When the mouth is closed, the upper front teeth should slightly overlap the lower front teeth, covering about one-third of the lower teeth. The upper molars should fit precisely into the grooves of the lower molars, ensuring even pressure during chewing. This balanced alignment promotes efficient chewing, clear speech, and comfort.
Malocclusions deviate from this ideal alignment, affecting how upper and lower teeth meet. Deviations can stem from an imbalance between jaw and tooth size, or an improper jaw shape. Genetic factors, like inherited jaw size, tooth shape, and alignment, can influence how teeth develop. Certain habits, such as prolonged thumb sucking, pacifier use in childhood, or early tooth loss, can also contribute to malocclusions by influencing tooth and jaw development.
Common Forms of Malocclusion
One common type of malocclusion is an overbite (Class II malocclusion), where the upper front teeth significantly overlap the lower front teeth. An excessive overbite involves the upper teeth extending more than 2-3 millimeters beyond the lower teeth, sometimes causing them to bite into the lower gums. Conversely, an underbite (Class III malocclusion) occurs when the lower front teeth protrude beyond the upper front teeth. This results from an oversized lower jaw or an undersized upper jaw.
A crossbite is another form of malocclusion where some upper teeth bite inside or outside the lower teeth, affecting either the front or back teeth, and can occur on one or both sides of the mouth. An open bite is characterized by a visible gap between the upper and lower teeth when the mouth is closed, meaning they do not touch at all. This can impact biting and chewing, particularly with foods like sandwiches.
Crowding happens when there is insufficient space in the jaw for all teeth to align normally, leading to overlapping or crooked teeth. This is a common orthodontic condition. Spacing, or diastema, refers to noticeable gaps between teeth, which can occur between any two teeth but is seen between the upper front two teeth. Both crowding and spacing indicate a misalignment that can affect oral hygiene and overall bite function.
Distinguishing Malocclusions from Other Oral Conditions
It is important to differentiate malocclusions, which are structural misalignments of teeth and jaws, from other oral health issues that do not involve such alignment problems. Temporary discomfort, such as that caused by erupting wisdom teeth, does not constitute a malocclusion. Similarly, minor irregularities in tooth shape or size that do not compromise the bite or jaw alignment are normal variations rather than true malocclusions.
Dental diseases like cavities are holes in teeth resulting from decay caused by acids wearing down enamel. While severe decay or premature tooth loss due to caries can sometimes contribute to changes in dental arch length or midline deviation, the cavity itself is a localized tooth issue, not a misalignment of the bite. Gum disease, including gingivitis and periodontitis, involves inflammation and infection of the tissues supporting the teeth, caused by plaque buildup. Although misaligned teeth can make cleaning difficult and thus increase the risk of gum disease, gum disease itself is a condition of the soft tissues and bone surrounding teeth, not a structural bite alignment problem.
Bruxism, or teeth grinding and clenching, is a habit that can cause tooth wear, jaw pain, and affect the temporomandibular joint (TMJ). While some suggest a connection, current research indicates no direct causal relationship between bruxism and malocclusion, as bruxism is primarily linked to psychosocial or physiological factors. The presence of missing teeth (anodontia/hypodontia) or extra teeth (supernumerary teeth) is also not a malocclusion. However, if missing teeth are not replaced, adjacent teeth can drift into the empty space, leading to shifting, spacing issues, and a subsequent malocclusion. Conversely, extra teeth can cause crowding, which is a malocclusion.