What is the recommended treatment for a patient with unilateral crossbite, specifically using braces wire bending (orthodontic wire bending)?

Treatment of Unilateral Crossbite with Orthodontic Wire Bending

For unilateral posterior crossbite, wire bending alone is insufficient and not recommended; instead, maxillary expansion using a removable expansion plate or fixed expander is the evidence-based treatment of choice, particularly when initiated in the late deciduous or early mixed dentition stage.

Primary Treatment Approach

Maxillary expansion, not wire bending, is the definitive treatment for functional unilateral posterior crossbite (FUPC). The evidence consistently demonstrates that symmetric expansion of the maxillary arch is required to correct the underlying skeletal and dental asymmetry 1, 2.

Standard Treatment Protocol

• Use a removable expansion plate with flat occlusal coverage of posterior teeth bilaterally, which corrects the crossbite in approximately 7 months followed by 6 months of retention 2
• Alternatively, use a fixed palatal expander (rapid maxillary expansion device) cemented intraorally, ideally before puberty after permanent first molars have erupted (typically 6-7 years of age) 3
• Treatment must include elimination of the mandibular functional shift and removal of selective occlusal interferences, not just dental movement 1

Why Wire Bending Fails

Wire bending addresses only the dental component and cannot:

• Correct the underlying maxillary constriction (narrow, high palate) 3
• Eliminate the mandibular functional shift that characterizes true unilateral crossbite 1, 2
• Achieve symmetric maxillary expansion needed for stable correction 1

Optimal Timing

Treat in late deciduous or early mixed dentition (ages 5-8 years) for maximum success and stability 1, 4.

• Treatment success rates exceed 90% when initiated early 1, 2
• Crossbites are not self-correcting and lead to skeletal, dental, and muscle adaptations if left untreated 1
• Early treatment prevents the need for combined orthodontics and surgery in adulthood 1

Diagnostic Requirements Before Treatment

Essential Clinical Findings

• Document the mandibular shift direction - there is strong correlation between crossbite side and direction of the retruded contact position (RCP) to intercuspal position (ICP) slide 2
• Assess arch width asymmetry - the crossbite side is narrower in the upper jaw but broader in the lower jaw compared to the non-crossbite side 4
• Evaluate skeletal pattern - children with larger SNB angles and smaller ANB angles have higher risk of non-correction even with expansion 4

Required Imaging

• Panoramic radiography and lateral cephalogram are necessary for orthodontic diagnosis and treatment planning 3
• CBCT is NOT indicated for routine unilateral crossbite cases unless severe craniofacial dysmorphosis is present 3

Treatment Algorithm by Age and Severity

Ages 5-8 Years (Deciduous/Early Mixed Dentition)

1. First-line: Removable expansion plate with occlusal coverage 2
2. Activate for 7 months on average
3. Retain for 6 months after correction
4. Monitor for stability through adolescence

Ages 8-12 Years (Mixed Dentition)

1. Fixed palatal expander (rapid maxillary expansion) 3
2. Activate expansion screw for 1-2 weeks
3. Leave device in place for several weeks without activation to consolidate expansion
4. Follow with fixed appliances for detailing if needed 5

Adults (Post-Pubertal)

1. Orthodontic expansion assisted by unilateral corticotomy on the crossbite side 6
2. Apply palatal expander and self-ligating brackets
3. Perform corticotomy at buccal aspect of crossbite side
4. Administer low-level laser therapy monthly until correction achieved
5. This achieves significantly greater expansion on crossbite side (P < 0.05 at premolar and molar levels) 6

Critical Pitfalls to Avoid

• Never attempt wire bending as primary treatment - it cannot address the skeletal maxillary constriction that defines unilateral crossbite 3, 1
• Do not delay treatment - crossbites become increasingly difficult to treat without surgery after skeletal maturity 1
• Watch for Class III tendency - these patients have higher relapse risk even with proper expansion 2
• Ensure symmetric expansion - asymmetric approaches fail because the underlying pathology involves bilateral maxillary constriction despite unilateral clinical presentation 1

Expected Outcomes and Stability

• Crossbite correction remains stable for average 8 years post-retention in 93% of early-treated cases 2
• Functional improvements include normalized occlusal force balance, improved masticatory muscle activity, and normalized chewing patterns 5
• However, correction does not guarantee absence of TMD at later ages, though early treatment optimizes growth and development 2

When Expansion May Fail

Children with the following characteristics at age 5 have higher non-correction rates despite expansion 4:

• Narrow crossbite side in upper arch combined with broad crossbite side in lower arch
• Larger SNB angle and smaller ANB angle compared to controls
• Significant skeletal Class III pattern

In these cases, consider early referral to orthodontist for comprehensive treatment planning that may require orthognathic surgery in adolescence 1.