The alignment of teeth and jaws is medically termed occlusion; imperfect alignment is known as a malocclusion. An overbite is a common form of malocclusion, characterized by an abnormal vertical relationship where the upper front teeth extend excessively over the lower front teeth when the jaw is closed. While a slight overlap is normal and beneficial for proper dental function, an overbite represents an exaggerated version of this vertical positioning. This issue can affect individuals of any age and may range from mild to severe, often requiring professional intervention.
Defining the Vertical Overlap
An overbite is the excessive vertical overlap of the maxillary (upper) front teeth over the mandibular (lower) front teeth. It is also commonly referred to as a deep bite because the lower teeth appear deeply covered by the upper teeth. A normal vertical overlap typically measures between one and three millimeters, or about 20% to 30% coverage of the lower incisors.
Dental professionals measure the severity using a millimeter scale or a percentage of coverage. An overlap exceeding three millimeters or covering more than one-third of the lower teeth is classified as an excessive overbite. This measurement helps determine the extent of the misalignment and the appropriate treatment strategy.
Overbite must be distinguished from overjet, as they describe different planes of misalignment. Overbite refers to the vertical distance between the upper and lower teeth. In contrast, overjet describes the horizontal protrusion, or the gap between the upper and lower front teeth. Overbite is concerned with how much the upper teeth cover the lower teeth, while overjet is concerned with how far the upper teeth stick out forward.
Factors Contributing to an Overbite
The development of an overbite is often multifactorial, stemming from genetic, dental, and habitual influences. Skeletal factors play a role, particularly inherited traits that dictate the size and shape of the jaws. A common skeletal cause involves a lower jaw that is disproportionately smaller or positioned too far back relative to the upper jaw, known as retrognathism.
Dental factors contribute when teeth erupt in a way that encourages excessive vertical overlap. This can include the over-eruption of the upper or lower incisors, or the under-eruption of the back molar teeth. The premature loss of baby teeth or the subsequent shifting of permanent teeth can also disrupt alignment and lead to a deep bite.
Prolonged childhood habits represent acquired factors that influence dental development. Habits such as extended thumb sucking or pacifier use, especially past the age of three, exert pressure that can push the front teeth into an abnormal position. Tongue thrusting, where the tongue pushes excessively against the back of the front teeth during swallowing, is another habitual factor contributing to this vertical misalignment.
Health and Aesthetic Implications
An untreated overbite can lead to a range of functional and health issues. A significant functional problem is abnormal wear on the teeth. The excessive overlap causes the lower front teeth to strike the back of the upper front teeth with undue force, leading to premature enamel wear, chipping, and fracturing over time.
In severe deep bite cases, the lower teeth can repeatedly bite into the gum tissue behind the upper teeth, causing irritation, recession, and trauma known as gingival impingement. This constant pressure can damage the soft tissues and increase the risk of periodontal issues. The misalignment can also strain the jaw joints, potentially leading to discomfort or pain associated with the temporomandibular joint (TMJ) and chronic headaches.
Functional difficulties often include compromised chewing efficiency and, in pronounced cases, speech impediments. Certain sounds require precise tongue and tooth placement, which can be hindered by a significant vertical overlap. A deep overbite can also affect the facial profile, sometimes giving the appearance of a sunken lower face or a less prominent chin, impacting a person’s self-confidence.
Methods for Correction
Correcting an overbite typically involves orthodontic treatment aimed at reducing the vertical overlap and establishing a balanced bite. Traditional metal or ceramic braces are effective, using brackets and wires to apply continuous force to reposition the teeth. Clear aligners, such as Invisalign, offer a discreet option and are suitable for correcting mild to moderate dental overbites.
Specialized orthodontic appliances are frequently used, particularly in growing patients. Bite plates are removable devices that cover the biting surfaces of the teeth, preventing the lower teeth from fully engaging and allowing the back teeth to erupt or the front teeth to be depressed. Growth modification appliances, often used in children and adolescents, help guide the development of the jaws to improve their skeletal relationship.
For severe overbites caused by a significant skeletal discrepancy—where the jaw bones themselves are misaligned—orthodontic treatment alone may be insufficient. In these adult cases, orthognathic surgery, or jaw surgery, may be required to reposition the upper, lower, or both jaws for proper alignment. The choice of treatment depends on the patient’s age, the underlying cause, and the severity of the vertical overlap.