Management of Crossbite

Definition

Classification

1. Anterior Crossbite

A. Dental Anterior Crossbite

• Class I molar and canine relation
• SNA, SNB, ANB within normal limits
• Abnormal axial inclination of affected teeth

• Tongue blade therapy - simple tipping in primary dentition; patient activates the labial movement of the upper tooth
• Catalan's appliance (inclined bite plane) - acrylic inclined plane bonded to lower anteriors; used in mixed dentition
• Z-spring / T-spring removable appliance - delivers labial force to palatally displaced upper tooth
• Fixed 2x4 appliance - brackets on upper incisors + bands on first molars; most controlled and efficient in mixed dentition
• Clear aligners - effective in adults with mild-to-moderate dental crossbite

B. Functional (Pseudo-Class III) Anterior Crossbite

• Mandible shifts forward from CR to CO (premature contact drives the shift)
• Patient can achieve edge-to-edge in CR
• Class III molar in CO, Class I in CR

• Upper removable appliance with inclined plane - redirects the mandible posteriorly
• Catalan's appliance - forward tipping of upper incisors
• 2x4 fixed appliance - preferred in mixed dentition
• Frankel III (FR-3) appliance - functional appliance; inhibits mandibular growth while stimulating maxillary forward growth
• Face mask (reverse-pull headgear) - used with bonded RPE; applies approximately 400-600 g force per side at 30 degrees downward to protract the maxilla; most effective before age 10 when sutures are still patent

C. Skeletal Anterior Crossbite (True Class III)

• Class III in both CR and CO; cannot achieve edge-to-edge in CR
• Concave profile, retrusive upper lip, negative ANB angle

• Growing patient (early/mixed dentition): Face mask + RME is the gold standard. Optimal before age 10. Can achieve 2-3 mm of maxillary advancement.
• Growing patient (Class III, more severe): Chin cup appliance (mandibular growth restraint) - more useful in mild skeletal Class III with a strong horizontal mandibular growth pattern
• Post-growth adolescent/adult: Comprehensive fixed orthodontic treatment ± orthognathic surgery (Le Fort I maxillary advancement + bilateral sagittal split osteotomy [BSSO] for mandibular setback, or combined bimaxillary surgery)

2. Posterior Crossbite

Etiology

• Digit/pacifier sucking habits
• Mouth breathing (low tongue posture)
• Premature loss of deciduous teeth
• Genetic/skeletal maxillary hypoplasia

A. Dental Posterior Crossbite (1-2 teeth involved)

• Crossbite elastics (Class III elastics on involved teeth)
• Removable appliance with coffin spring or Z-spring
• Fixed appliances with bracket repositioning

B. Bilateral Posterior Crossbite (Maxillary Constriction)

C. Unilateral Posterior Crossbite with Functional Shift

• Eliminate the shift first (equilibration or RME)
• RME will usually auto-correct the functional shift
• After symmetrical expansion, functional shift disappears and mandible auto-corrects to midline

D. Adult Posterior Crossbite (Skeletally Mature)

• SARPE (Surgically Assisted Rapid Palatal Expansion): Corticotomy of the lateral walls, pterygoid plates ± midpalatal osteotomy followed by gradual expansion with a hyrax device. Mean expansion ~6.8 mm. Effective, stable, improves nasal airway.
• Two-piece Le Fort I osteotomy: Precise expansion of only the posterior segment where needed; less overall expansion but targeted correction
• Le Fort I + BSSO (orthognathic surgery): For severe skeletal discrepancy requiring simultaneous anteroposterior and transverse correction

3. Treatment Decision Summary by Age

4. Retention

• After RME: retain with a fixed transpalatal arch or Hawley retainer for at least 6-12 months (bone fills in 3-6 months)
• After 2x4/bracket correction of anterior crossbite: standard retainers
• After orthognathic surgery: rigid fixation provides stability; orthodontic finishing retainer post-surgically

Key Clinical Points

• Early treatment is preferred for all crossbites - functional shifts, if left uncorrected, can lead to true facial asymmetry and permanent TMJ adaptation
• Differential diagnosis between dental, functional, and skeletal crossbite is the most important step before treatment planning
• Face mask + RME works best before age 10; effectiveness drops sharply after adolescent growth spurt
• SARPE vs. 2-piece Le Fort I - SARPE is preferred when the entire maxilla needs expansion; 2-piece Le Fort I is better when only posterior expansion is needed in a patient already requiring orthognathic surgery
• The presence or absence of a functional shift (CR-CO discrepancy) changes both prognosis and appliance choice significantly