An underbite, clinically known as a Class III malocclusion, is a dental misalignment where the lower jaw and teeth extend beyond the upper jaw and teeth. This means the lower front teeth protrude in front of the upper front teeth when the mouth is closed. An underbite represents a structural deviation from typical jaw alignment, making the lower jaw appear more prominent.
Key Visual Characteristics
A primary visual indicator of an underbite is the noticeable protrusion of the lower jaw, which makes the chin appear more prominent. When viewed from the side, a person with an underbite may display a concave facial profile, where the middle part of the face seems recessed while the chin juts forward. This can create an unbalanced facial appearance.
The alignment of the teeth offers another clear sign. The lower front teeth rest in front of or overlap the upper front teeth, rather than behind them. This can range from a slight overlap to a significant gap where the upper and lower teeth do not make proper contact. The upper lip or jaw might also appear “pushed in” in contrast to the forward lower jaw.
Distinguishing an Underbite
A normal bite, or Class I occlusion, is characterized by the upper front teeth slightly overlapping the lower front teeth, typically by about 1-2 millimeters. In this ideal alignment, the upper teeth fit just over the bottom teeth.
An overbite, by contrast, occurs when the upper front teeth significantly overlap the lower front teeth. This condition, also known as a Class II malocclusion, makes the upper jaw and teeth appear to extend far beyond the lower ones. Visually, an overbite can sometimes result in a recessed chin or a “buck teeth” appearance, distinct from the forward-jutting chin of an underbite.
An underbite is the inverse of an overbite, where the lower teeth and jaw are positioned in front of the upper teeth. This direct opposition in jaw and tooth alignment provides a clear visual distinction. While an overbite shows excessive vertical overlap of the upper teeth, an underbite displays the lower teeth horizontally forward of the upper teeth.
Spectrum of Underbite Appearance
Underbites exist on a spectrum from mild to severe, varying in their visual presentation. A mild underbite might present with only a subtle forward positioning of the lower jaw or a minimal overlap of the lower teeth over the upper teeth. In some mild instances, the misalignment may be barely noticeable.
As an underbite progresses in severity, its visual impact becomes more pronounced. A severe underbite involves a significant forward shift of the lower jaw and a noticeable facial imbalance. This can lead to a very prominent chin and a distinct concave facial shape. Even slight visual cues, such as a lower jaw that appears to jut out, can indicate the presence of an underbite.
When to Seek Professional Guidance
Observing visual signs of a potential underbite warrants a consultation with a dental professional, such as a dentist or orthodontist. Early intervention is often recommended, particularly for children, as their jaws are still developing. An orthodontic screening, ideally around age seven when adult front teeth begin to emerge, can help identify and address issues.
Professional diagnosis goes beyond visual inspection, involving detailed examinations and potentially X-rays to accurately assess the alignment of teeth and jaw structures. This initial consultation focuses on proper diagnosis and discussing potential options, rather than immediately initiating treatment.