Malocclusion, or a “bad bite,” is a common dental condition referring to any misalignment of the upper and lower teeth when the jaws are closed. An overbite is one of the most frequently encountered types, involving a vertical discrepancy where the upper teeth overlap the lower teeth. This article will focus on the distinct visual characteristics of this misalignment, how it is classified, and the factors that contribute to its development.
Identifying Excessive Vertical Overlap
An overbite is defined by the degree of vertical overlap, where the upper front teeth cover the lower front teeth when the mouth is closed. A normal, healthy bite involves the upper teeth covering only 10 to 20% of the visible surface of the lower incisors. This slight overlap (one to three millimeters) is considered ideal for proper chewing function and protecting soft tissues.
When this vertical coverage exceeds the normal range, it is classified as an excessive overbite, or a deep bite. A moderate overbite is indicated when the overlap measures four to eight millimeters, or when the upper teeth cover more than 30% of the lower teeth. The lower front teeth may appear partially hidden or significantly obscured by the upper dental arch.
A severe overbite occurs when the upper teeth completely hide the lower teeth, sometimes overlapping by more than nine millimeters. In extreme instances, the lower incisors may damage the gum tissue behind the upper front teeth. This degree of malocclusion can contribute to a visually recessed or smaller appearance of the lower jaw, clinically known as a Class II malocclusion.
Overbite Versus Overjet: Understanding Directional Differences
A common source of confusion is mistaking an overbite for an overjet, yet they describe two different directional issues. The overbite addresses the vertical relationship (depth of overlap), while the overjet describes the horizontal relationship (how far the upper teeth protrude forward). Overjet measures the horizontal distance between the front surface of the lower teeth and the back surface of the upper teeth.
An excessive overjet is the condition colloquially referred to as “buck teeth,” where the upper front teeth visibly jut out significantly ahead of the lower teeth. A healthy overjet measurement is about two to three millimeters, meaning the upper teeth rest slightly forward of the lower teeth.
It is possible for a person to have both an excessive overbite and an excessive overjet simultaneously, meaning the upper teeth are both too far down and too far forward.
Primary Causes and Associated Symptoms
The development of an overbite often stems from a combination of genetic factors and environmental influences affecting jaw development.
Causes
Genetics plays a substantial role by predetermining the size and shape of the jaws. This can lead to a discrepancy where the lower jaw is naturally smaller or positioned further back than the upper jaw, resulting in skeletal misalignment.
Environmental factors, particularly during early childhood, also contribute to the misalignment. Prolonged habits such as persistent thumb-sucking, excessive pacifier use past the toddler years, or chronic tongue-thrusting exert pressure on the developing teeth and jawbones. These habits can physically push the upper front teeth forward or prevent the lower jaw from developing to its full potential size.
Associated Symptoms
Beyond the visible changes to the teeth, an overbite can cause a variety of physical symptoms related to compromised function. The misalignment can lead to abnormal or uneven wear patterns on the enamel of the teeth, potentially causing premature erosion.
Individuals may experience difficulties with speaking (such as developing a lisp) or trouble chewing certain types of food effectively. The strained relationship between the jaws can also put excessive stress on the temporomandibular joints (TMJ), resulting in chronic jaw pain and headaches.