How is an underbite (malocclusion) corrected?

Treatment of Underbite (Class III Malocclusion)

Underbite correction depends critically on skeletal maturity: growing children benefit most from facemask therapy to advance the upper jaw, while skeletally mature patients with severe deformity require orthognathic surgery combined with orthodontics. 1

Treatment Approach by Age and Severity

Growing Children and Adolescents (≤16 years)

Facemask therapy is the primary treatment for skeletal Class III malocclusion in growing patients, showing significant improvement in jaw relationships. 1

• Facemask treatment produces a mean improvement of 4.10 mm in overjet (95% CI 3.04 to 5.16) compared to no treatment, with benefits maintained at 3-year follow-up. 1

• Angular jaw relationship (ANB) improves by 3.93° (95% CI 3.46 to 4.39) with facemask therapy, indicating substantial correction of the skeletal discrepancy between upper and lower jaws. 1

• Chin cup therapy also demonstrates statistically significant improvement in ANB and Wits appraisal (another measure of jaw relationship) in growing patients. 1

• Treatment timing is critical: earlier intervention during active growth phases yields optimal results, as the appliances work by redirecting jaw growth rather than moving already-formed bone. 1

Skeletally Mature Patients (Post-Growth)

Orthognathic surgery combined with orthodontics is indicated for adults and post-growth adolescents with moderate-to-severe skeletal Class III malocclusion. 2, 3

Surgical Options Based on Severity:

• Mandibular setback surgery alone (Obwegeser/Dal Pont procedure) for primarily mandibular excess, with a relapse rate of 21%. 3

• Bimaxillary surgery (Le Fort I maxillary advancement + mandibular setback) for combined maxillary deficiency and mandibular excess, with a relapse rate of 24%. 3

• Maxillary advancement procedures show superior stability with lower relapse rates (21%) compared to mandibular procedures (27%), making them preferable when both options are viable. 3

Critical Surgical Considerations:

• Relapse correlates positively with the magnitude of mandibular setback: larger movements have higher relapse risk, requiring careful surgical planning. 3

• Orthodontic preparation is essential: pre-surgical orthodontics aligns the dental arches, and post-surgical orthodontics refines the occlusion. 3, 4

• Skeletal maturity must be confirmed before surgery to prevent growth-related relapse. 2

Treatment Algorithm for Dentofacial Deformity

Mild-to-Moderate Deformity in Growing Patients:

1. Initiate dentofacial orthopedic appliances (facemask or chin cup) early when deformity is first detected to maximize growth modification potential. 2, 1

2. Combine with anti-inflammatory therapy if temporomandibular joint (TMJ) involvement is present, as this can affect mandibular growth. 2

3. Monitor with serial cephalometric radiographs to assess treatment response and growth patterns. 2

Severe Deformity or Skeletally Mature Patients:

1. Confirm quiescent/controlled TMJ status before surgical intervention, as active inflammation increases surgical complications. 2

2. Complete pre-surgical orthodontics to decompensate dental positions and prepare arches for surgical repositioning. 3, 4

3. Select surgical approach based on:

   • Maxillary advancement preferred when feasible due to superior stability. 3
   • Bimaxillary surgery for combined skeletal discrepancies. 3
   • Consider distraction osteogenesis in severe cases or when traditional orthognathic surgery is contraindicated. 2

4. Post-surgical orthodontic refinement for 6-12 months to optimize occlusion. 3

Common Pitfalls and How to Avoid Them

• Do not delay treatment in growing patients: early intervention with growth modification appliances is most effective, and waiting until skeletal maturity necessitates surgery. 1

• Avoid underestimating relapse potential: mandibular setback distances >6-8 mm have significantly higher relapse rates, requiring consideration of alternative approaches or overcorrection. 3

• Ensure proper occlusal assessment post-treatment: verify that posterior teeth fully interdigitate and that the patient can achieve proper bite closure without interference. 5

• Do not perform orthognathic surgery with active TMJ arthritis: this significantly increases complications and relapse risk; optimize inflammatory control first. 2

• Account for missing teeth in treatment planning: implant placement or prosthetic reconstruction may be needed before or after orthodontic/surgical correction to establish proper occlusion. 6, 4

Monitoring and Long-Term Stability

• All patients require long-term retention following active treatment, as relapse can occur years after treatment completion. 3

• Monitor for TMJ complications, particularly in surgical cases, as joint dysfunction can develop post-operatively. 2

• Serial cephalometric evaluation at 6-month to 1-year intervals during the first 2-3 years post-treatment helps detect early relapse. 3