An underbite, medically known as mandibular prognathism, is a common orthodontic concern where the lower jaw and teeth sit forward of the upper jaw and teeth. This misalignment results in the lower teeth overlapping the upper teeth when the mouth is closed, creating a reversed bite pattern. Though often considered a cosmetic issue, an untreated underbite can lead to difficulty chewing, excessive tooth wear, and jaw joint problems. The answer depends entirely on the underlying cause and severity of the misalignment, which is critical for determining the appropriate treatment path.
Defining the Types of Underbite
Orthodontists classify an underbite as a Class III Malocclusion, which is a structural relationship where the lower dental arch is positioned ahead of the upper dental arch. This condition can stem from issues related either to the positioning of the teeth or the structure of the jawbones. Understanding this distinction is fundamental because it dictates whether conventional braces will be sufficient or if more advanced interventions are necessary.
A Dental Underbite is characterized by a misalignment primarily confined to the teeth themselves, while the underlying jaw structure is reasonably well-positioned. In these cases, the lower jawbone, or mandible, is usually in a normal position, but the lower front teeth have tilted too far forward or the upper front teeth have tilted inward. This type of underbite is typically mild.
A Skeletal Underbite presents a more complex issue, as the discrepancy is rooted in the size or position of the jawbones. This can be caused by an overgrowth of the lower jaw, an underdevelopment or retrusion of the upper jaw, or a combination of both factors. Because the misalignment involves the bone structure, a skeletal underbite is often more severe and tends to be heavily influenced by genetic inheritance. The extent of the skeletal problem significantly impacts the viability of non-surgical treatment options.
The Role of Braces in Correction
Braces are a highly effective treatment for an underbite when the issue is primarily dental or mild in nature. For a dental underbite, fixed orthodontic appliances work by gradually repositioning the teeth to achieve a proper bite alignment. The orthodontist will strategically use the wires and brackets to push the upper front teeth slightly forward while simultaneously pulling the lower front teeth slightly backward.
This tooth movement attempts to “camouflage” the underlying jaw relationship by correcting the way the top and bottom teeth meet. Treatment may also incorporate specialized elastics that connect the upper and lower arches in a reverse-pull pattern. These elastics run from the upper arch toward the front of the mouth to the lower arch toward the back, exerting force to encourage the desired movement and alignment. This approach is most successful when treating younger patients or adults with minor discrepancies. The goal is to establish a positive overjet, where the upper teeth overlap the lower teeth slightly, improving both function and aesthetics. While braces are powerful tools for tooth movement, their ability to correct major structural jaw differences is limited.
Advanced Treatments for Skeletal Misalignment
Pediatric Intervention (Ages 7-10)
When the underbite is skeletal, treatment is highly dependent on the patient’s age. Pediatric intervention is typically initiated around ages seven to ten, capitalizing on the child’s remaining growth potential. A common appliance is the reverse-pull headgear, or facemask, which attaches to the upper jaw and applies forward-directed force. This device stimulates the forward growth of the underdeveloped upper jaw (maxilla) while gently restraining the forward growth of the lower jaw. Palate expanders are often used concurrently to widen the upper arch, creating more space and improving the effectiveness of the facemask.
Surgical Orthodontics (Adults and Severe Cases)
For adults or severe cases where the jaw discrepancy is too significant and growth has ceased, the definitive solution is often orthognathic surgery. This procedure physically repositions the upper and/or lower jawbones to achieve proper alignment. Braces are still a part of the treatment, used both before and after surgery to ensure the teeth are aligned perfectly within the newly positioned jaws. This combined approach, known as surgical orthodontics, is reserved for the most complex skeletal underbites that cannot be corrected by tooth movement or growth modification alone.