Prediction of treatment outcome following correction of anterior crossbites in the mixed dentition: orthodontic versus orthopaedic methods

AIM: To separate subjects with anterior crossbite and mild maxillary deficiency into two groups: those that can be treated successfully with a 2 x 4 appliance and those that should be treated with reverse headgear and maxillary expansion. METHODS: Thirty mixed dentition subjects each with an anterior crossbite, a concave profile, a deficient maxilla, and an ANB angle between -2 and +1 degrees were used. Fifteen subjects (8 boys, 7 girls; Mean age: 9.17 +/- 1.1 years) were successfully treated with a 2 x 4 appliance (orthodontic treatment group) and remainder (5 boys, 10 girls; Mean age: 8.6 +/- 1.5 years) were successfully treated with reverse headgear and maxillary expansion after initial treatment with a 2 x 4 appliance had failed (orthopaedic treatment group). Unstandardised discriminant function coefficients and a constant were calculated for selected pretreatment cephalometric variables. RESULTS: The NSAr angle was significantly smaller (p < 0.01) and both anterior and posterior cranial base lengths were significantly longer in the orthodontic treatment group (p < 0.001) compared with the orthopaedic group. The prediction index developed was: (PI) = -0.2 NSAr + 0.243 S-N + 0.187 S-Ar + 3.366. The critical score was 0. With positive scores a 2 x 4 appliance can be used and with negative scores reverse headgear and expansion are indicated. CONCLUSION: An equation able to predict treatment success with either a 2 x 4 appliance or reverse headgear has been developed.