An underbite, clinically known as a Class III malocclusion, is a dental condition where the lower teeth and lower jaw protrude past the upper teeth when the mouth is closed. This occurs because the upper jaw (maxilla) is often underdeveloped, the lower jaw (mandible) is overdeveloped, or a combination of both. While surgery has long been a solution for severe cases, many patients can achieve successful correction through non-surgical orthodontic methods. The viability of non-surgical treatment depends heavily on the patient’s age and the underlying cause of the jaw misalignment.
Early Intervention Through Growth Modification
The most effective opportunity for non-surgical correction of an underbite exists during the childhood growth phase. This period, typically between seven and ten years of age, is when the jaw bones are pliable and responsive to orthopedic forces. Treatment at this stage is known as interceptive orthodontics, focusing on modifying the direction of skeletal growth rather than just moving teeth.
The primary goal of early intervention is to move the upper jaw forward and potentially restrict the forward growth of the lower jaw. A common and effective appliance for this purpose is the reverse-pull headgear, often referred to as a facemask. The facemask is an external orthopedic device that connects to the teeth or a palatal expander inside the mouth using elastics.
These elastics apply a gentle, forward-directed force to the underdeveloped maxilla, stimulating its growth and bringing it into a more balanced relationship with the lower jaw. Facemask therapy can lead to a significant increase in the forward positioning of the upper jaw, measured by a change in the ANB angle on a cephalometric X-ray. The appliance is generally worn for a set number of hours per day, often including all sleeping hours, for a period lasting between nine and twelve months.
Another appliance used, particularly in some Asian populations, is the chin cap, which applies a restraining force to the lower jaw. The chin cap aims to redirect the growth of the mandible, causing it to rotate slightly downward and backward, which can help reduce its prominence. This redirection of growth can improve the jaw relationship during the mixed dentition phase. Combining these orthopedic treatments with fixed braces often maximizes the stability of the result and reduces the chances of needing surgery later in life.
Orthodontic Camouflage for Mature Patients
Once a patient’s skeletal growth has finished, typically in adolescence or adulthood, true skeletal correction without surgery is no longer possible. At this stage, non-surgical treatment shifts its focus to “orthodontic camouflage,” which is purely dental movement used to mask the underlying jaw discrepancy. Camouflage treatment uses appliances like traditional braces or clear aligners to position the teeth in a way that allows them to meet properly, even if the jaw bones are misaligned.
In an underbite case, this usually involves tipping the upper front teeth slightly forward and the lower front teeth slightly backward to correct the reverse overlap. This movement creates a functional bite by changing the angle of the teeth in their sockets, known as dentoalveolar compensation. This compensation allows the upper teeth to overlap the lower teeth correctly, correcting the anterior crossbite.
To achieve controlled tooth movement, orthodontists often use auxiliary appliances, such as elastics worn between the upper and lower arches. More advanced techniques utilize Temporary Anchorage Devices (TADs), which are small, temporary titanium screws placed into the jawbone. TADs act as a fixed anchor point, providing stable resistance that allows the orthodontist to apply precise forces to retract the lower teeth or protract the upper teeth.
While camouflage can be highly successful for mild to moderate underbites, it is essentially a compromise that prioritizes dental function and appearance over skeletal alignment. The extent of the camouflage is restricted by the biological limits of the surrounding bone and gums. Pushing the teeth too far out of their natural position can compromise the stability of the teeth, potentially leading to gum recession or root shortening.
Skeletal Severity and Treatment Limits
Whether surgery is necessary ultimately comes down to the severity of the skeletal discrepancy. Orthodontists use specific measurements, often taken from a cephalometric X-ray, to classify the misalignment as either a “dental” or a “skeletal” underbite. A dental underbite is one where the teeth are the primary problem, and camouflage works well because the jaw relationship is only slightly off.
A skeletal underbite, however, involves a significant mismatch in the size or position of the maxilla and mandible. Specific cephalometric values, such as the ANB angle, which relates the position of the upper and lower jaws, help determine the severity. For instance, a patient with an ANB angle below a certain negative degree, or a Wits appraisal measurement below a specific negative millimeter, is often considered a candidate for surgical intervention.
The limit for non-surgical camouflage is reached when the jaw misalignment is so pronounced that correcting the teeth alone would require excessive tipping, which is detrimental to the long-term health of the teeth and supporting tissues. Attempting to camouflage a severe skeletal problem can result in a poor facial profile or an unstable bite that may relapse over time. For these severe cases, orthognathic surgery—a procedure to physically reposition the upper or lower jaw, or both—is necessary to achieve a stable, functional, and aesthetically pleasing result.