A Case Of Full-Arch Crossbite Intervention In Mixed Dentition

Introduction: Early intervention for skeletal Class III malocclusion with complete crossbite in mixed dentition is critical to correct maxillary deficiency and prevent progressive worsening of the condition. This case report demonstrates the efficacy of combined maxillary expansion and protraction therapy in a 6-year-old patient, followed by functional appliance (FRIII) retention. The treatment aimed to address transverse and sagittal discrepancies simultaneously, leveraging growth modification during the transitional dentition phase. Case description: A 6-year-old girl presented with skeletal/dental Class III malocclusion (complete maxillary crossbite, with mandibular midline deviation (1mm right)). Treated with maxillary expansion (bonded RPE appliance) and facemask protraction (500g/side, 12h/day) for 8 months, followed by FRIII retention. Achieved crossbite correction, improved arch coordination, and minimal (0.5mm) residual midline deviation. Growth modification successfully addressed transverse/sagittal discrepancies during mixed dentition. Discussion: Early maxillary expansion-protraction leverages growth potential to correct transverse/anteroposterior discrepancies efficiently. FRIII retention maintains correction while permitting growth. RPE disrupts circummaxillary sutures, enhancing protraction efficacy (Turley 1988). Minor midline deviations may self-correct or need Phase II treatment. Short-term results are promising, but long-term stability requires adolescent monitoring. Conclusion/clinical significance: This case highlights the success of early two-phase therapy (expansion-protraction+FRIII) in resolving complete crossbite with skeletal involvement. The protocol optimizes growth modulation while minimizing future complications, underscoring the importance of interceptive treatment in mixed dentition.