How To Fix An Underbite: Clinical Treatments For Class III Malocclusion

Correcting an underbite—medically classified as a Class III malocclusion—requires shifting the dentition, repositioning the jawbones, or a coordinated combination of both therapeutic strategies. Depending on the patient's age and skeletal maturity, treatment options range from early pediatric orthopedic devices like reverse-pull facemasks to adult orthodontic compensation using bone screws, or corrective orthognathic surgery. Achieving an optimal positive overjet of 1 to 3 millimeters is the primary clinical benchmark for success, restoring masticatory function and facial balance.

Clinical Evaluation and Diagnostic Prerequisites for Underbite Correction

Treating an underbite successfully depends on distinguishing between a skeletal Class III malocclusion (where the lower jaw is structurally larger or positioned further forward than the upper jaw) and a dental Class III malocclusion (where the jaws are aligned, but the teeth tilt in a way that creates an underbite). A third scenario, pseudo-underbite, occurs when a patient shifts their jaw forward to avoid tooth interference when closing their mouth.

Before any treatment plan can be designed, a practitioner must perform a complete diagnostic workup. This stage defines the severity of the malocclusion, maps out the patient's skeletal growth potential, and establishes a clear baseline for treatment.

Diagnostic Tools and Clinical Indicators

• Lateral Cephalometric Radiography: Essential for measuring the angular and linear relationships of the skull. Key clinical metrics include the SNA angle (maxillary position relative to the cranial base), SNB angle (mandibular position relative to the cranial base), and the ANB angle (the skeletal relationship between the upper and lower jaws). A normal ANB angle is 2° to 4°; a negative ANB angle indicates a skeletal Class III underbite.
• Cone Beam Computed Tomography (CBCT): Used to obtain three-dimensional renderings of the temporomandibular joints (TMJ), airway space, and alveolar bone density, ensuring safe bone boundaries for tooth movement.
• Intraoral 3D Digital Scanners: Used to generate highly accurate digital impressions to assess tooth wear patterns, crossbites, and occlusion.
• Cervical Vertebral Maturation (CVM) Assessment: Evaluates the shape of the second, third, and fourth cervical vertebrae on a cephalometric X-ray. This metric determines whether a young patient has remaining skeletal growth potential (stages CVM 1 through 3) or if they have reached skeletal maturity (stages CVM 4 through 6).

Initial Prerequisites and System Requirements

• Periodontal Health: The patient must have healthy, stable gums with no active periodontal pocketing or bone loss.
• Caries Eradication: All active tooth decay must be treated, and any dental restorations must be completed before starting orthodontic treatment.
• TMJ Assessment: The temporomandibular joint must be stable and free of acute dysfunction or severe degeneration.
• Estimated Treatment Duration: 12 to 18 months for early interceptive pediatric treatment; 18 to 30 months for comprehensive adult orthodontics; 24 to 36 months for combined surgical-orthodontic cases.
• Financial Benchmarks: Costs vary from $3,000 to $8,000 for standard pediatric orthopedics or adult braces, up to $20,000 to $40,000+ for comprehensive surgical-orthodontic correction.

Step-by-Step Clinical Workflow for Correcting Class III Malocclusion

The exact path to correcting an underbite depends on the patient's skeletal age and the root cause of the malocclusion. Below is the comprehensive clinical sequence, organized by age groups, diagnostic categories, and treatment stages.

Step 1: Pediatric Interceptive Correction (Ages 7 to 10)

During the early mixed dentition stage (when patients have a mix of baby teeth and adult teeth), the circummaxillary sutures are still open. This provides an ideal window to guide jaw growth using orthopedic forces.

1. Maxillary Expansion: Install a Rapid Maxillary Expander (RME) on the upper molars. The patient or parent activates the expander by turning a central screw 0.25 millimeters once or twice daily for 2 to 3 weeks. This expansion widens the upper jaw and loosens the surrounding sutures, making it easier to pull the upper jaw forward.
2. Fitting the Reverse-Pull Facemask: Fit an external orthodontic facemask that rests on the patient's forehead and chin. Connect the facemask to the internal expander using intraoral elastics attached to hooks near the upper canine teeth.
3. Applying Orthopedic Force: Use heavy orthodontic elastics to apply a forward-pulling force of 400 to 500 grams per side. Direct the force downward and forward at an angle of 20 to 30 degrees relative to the chewing surface. This angle helps prevent the upper front teeth from tilting upward excessively.
4. Compliance and Monitoring: The patient must wear the facemask for 12 to 14 hours per day for 8 to 12 months. Progress is monitored using serial cephalometric X-rays until a positive overjet of 2 to 3 millimeters is achieved.

Warning: Attempting to pull the upper jaw forward with a facemask after the circummaxillary sutures have fused (typically after age 10 to 11) will not correct the underlying bone structure. Instead, it will cause the upper teeth to tilt forward excessively and can put stress on the roots.

Step 2: Non-Surgical Dental Compensation in Adults (Mild to Moderate Skeletal Discrepancy)

When a patient's jaw growth is complete, mild to moderate underbites can be corrected by tilting the teeth to camouflage the underlying skeletal discrepancy.

1. Arch Development and Bracket Placement: Place fixed orthodontic brackets (using Roth or MBT prescription specifications) or initiate a series of clear aligners with specialized attachment points.
2. Mandibular Distalization Using TADs: To move the entire lower arch backward, insert Temporary Anchorage Devices (TADs)—small titanium bone screws—into the bone of the lower jaw, either between the roots of the teeth or in the bone next to the lower molars.
3. Force Application: Run orthodontic elastics or coil springs directly from the TADs to the lower teeth. This setup pulls the lower teeth backward into the extra space without putting unwanted pressure on the other teeth.
4. Class III Elastic Support: Use Class III orthodontic elastics (running from the upper back molars to the lower front teeth) to help tip the upper teeth forward and pull the lower teeth backward. Monitor the angle of the lower incisors carefully to prevent them from tilting backward too far, which can compromise the surrounding bone.

Pro-Tip: Keep the angle of the lower incisors relative to the base of the lower jaw (the IMPA angle) above 80 degrees. Tipping the teeth back beyond this point can cause gum recession and push the roots of the lower teeth through the thin supporting bone on the inside of the jaw.

Step 3: Combined Surgical-Orthodontic Protocol (Severe Adult Skeletal Class III)

In cases of severe skeletal underbites in mature adults (where the discrepancy is greater than 5 millimeters), a combination of braces and orthognathic surgery is necessary to achieve a stable and functional bite.

1. Pre-Surgical Orthodontic Decompensation (12 to 18 Months): Place fixed orthodontic appliances to align the teeth within each individual jaw. This stage removes any natural dental compensation. It often temporarily worsens the appearance of the underbite, positioning the teeth properly over their supporting bone to prepare for surgical jaw movement.
2. Surgical Wafer Fabrication and Virtual Planning: Use 3D CBCT scans and digital software to plan the jaw movements. Print a surgical splint (or wafer) to guide the surgeon in precisely positioning the jaws during the procedure.
3. Surgical Execution (Double-Jaw Surgery):
   
   
   • Maxillary Advancement: The surgeon performs a Le Fort I osteotomy, freeing the upper jaw and moving it forward to correct any mid-face flatness.
   • Mandibular Setback: The surgeon performs a Bilateral Sagittal Split Osteotomy (BSSO) to move the lower jaw backward.
   • Rigid Fixation: Secure the jaws in their new, correct positions using titanium plates and bone screws.
4. Post-Surgical Orthodontic Refinement (6 to 9 Months): Once the jaw bones have healed (typically 6 to 8 weeks after surgery), use light orthodontic elastics to fine-tune the bite, establish ideal tooth-to-tooth contact, and achieve a stable, long-term result.

Comparing Underbite Correction Methods

Choosing the right treatment method depends heavily on the patient's skeletal age, compliance, and the severity of the underbite. The table below compares the primary clinical approaches used to correct Class III malocclusions.

Troubleshooting Complications and Treatment Failures

Even with careful diagnostic planning, underbite correction can run into issues due to unexpected growth, anatomical limits, or compliance challenges. Below are common clinical complications and their remedies.

Scenario 1: Lack of Forward Upper Jaw Movement During Facemask Therapy

• Root Cause: The patient is not wearing the device for the required hours, the elastic force is too weak, or the facial sutures have already fused due to an advanced skeletal age (CVM Stage 4 or later).
• Actionable Fix: Measure the elastic tension using a force gauge to confirm it is delivering 450 grams of force per side. If the patient is compliant but the bones are not moving because the sutures have fused, stop facemask therapy. Pivot to a bone-anchored maxillary protraction system (BAMP) using mini-plates, or delay skeletal correction until the patient is old enough for orthognathic surgery.

Scenario 2: Severe Gum Recession or Bone Loss Around the Lower Front Teeth

• Root Cause: The lower front teeth have been tilted backward too far during non-surgical compensation. This pushes the roots of the teeth out of the supporting bone envelope on the tongue side of the jaw.
• Actionable Fix: Stop using Class III elastics immediately. Use torque-controlling orthodontic archwires to upright the roots of the teeth back into the center of the supporting bone. If the bone loss is severe, refer the patient to a periodontist for a gum or bone graft to reinforce the tissue before continuing any orthodontic movement.

Scenario 3: Return of the Underbite After Orthognathic Surgery

• Root Cause: The surgery was performed before the patient finished growing, and the lower jaw continued to grow forward. Other causes include unstable placement of the surgical plates or structural changes in the temporomandibular joint (such as condylar resorption).
• Actionable Fix: Take updated CBCT scans to check the health and stability of the jaw joints. If the joints are stable and the relapse is minor, use braces or aligners with bone screws to make dental corrections. If the relapse is severe and caused by significant post-surgical jaw growth, plan a second orthognathic surgery once growth has completely stopped, confirming stability with consecutive bone scans taken one year apart.

Frequently Asked Questions

Can clear aligners alone fix an underbite?

Clear aligners can correct mild, purely dental underbites in adults by tipping the upper teeth forward and the lower teeth backward. However, if the underbite is caused by a structural jaw discrepancy (a skeletal Class III), clear aligners alone cannot fix the issue. In these cases, aligners must be used in combination with bone screws (TADs) or corrective jaw surgery to achieve a stable, functional result.

At what age is it too late to fix an underbite without surgery?

In patients with a structural skeletal underbite, the window for non-surgical jaw correction typically closes around age 10 to 12. Once the growth plates and facial sutures fuse, the jaws can no longer be guided into a new position. After this point, moderate to severe underbites generally require corrective orthognathic surgery once the patient has finished growing, usually after age 17 or 18.

How long does it take to fix an underbite using braces?

The timeline for correcting an underbite using braces depends on the complexity of the case. Mild dental corrections can take 12 to 18 months. Moderate cases that require moving the entire lower arch backward using bone screws typically take 18 to 24 months. Severe cases that combine braces with jaw surgery usually require a total treatment time of 24 to 36 months, which includes both pre-surgical and post-surgical orthodontic phases.

What happens if an underbite is left untreated?

Leaving an underbite untreated can lead to progressive wear and chipping of the front teeth, jaw joint pain (TMJ dysfunction), and difficulty chewing. Over time, the uneven forces on the teeth can cause premature tooth loss and gum recession. Severe underbites can also affect speech clarity, impact facial symmetry, and restrict airway volume, potentially contributing to obstructive sleep apnea.

Take the Next Step Toward Alignment

An untreated underbite can compromise your long-term dental health, leading to premature tooth wear and chronic jaw joint discomfort. Schedule a consultation with a qualified orthodontist or oral surgeon today to receive a personalized digital diagnostic scan and explore your treatment options.