Three-dimensional evaluation of slow maxillary expansion with leaf expander vs. rapid maxillary expansion in a sample of growing patients: Direct effects on maxillary arch and spontaneous mandibular response

The aim is to evaluate the effects of slow maxillary expansion on maxillary and mandibular arch, using a slow maxillary expander (SME-Leaf Expander) banded on primary second molar. Ninety patients with transverse maxillary deficiency and posterior crossbite were selected. Sixty-nine patients (33 males/36 females; 7.6 ± 1.7 years old) who underwent SME and 21 patients (10 males/ 11 females; 7.4 ± 1.2 years old) who were treated with rapid maxillary expander (RME). Digital models obtained pre-and post-treatment at appliance removal (9 to 11 months) were processed by means of a 3D scanner (Trios 3, 3Shape D250 laser, Copenhagen, Denmark). Interdental width in both maxilla and mandible were measured with 3 SHAPE Ortho Analyzer. Four Maxillary and four mandibular interdental width were traced and evaluated. The adequate Student's t-test (dependent or independent) was used to compare intra and intergroups interdental width differences (p < 0.05). The efficacy of the SME was confirmed both on maxillary and mandibular arch. All the maxillary and mandibular interdental widths increased significantly (p < 0.001). The comparison with the RME group showed significant statistical differences between the two treatments with a greater increase in primary first and second intermolar and canine width for the test group (p < 0.001). SME with Leaf Expander produced statistically significant effects for the correction of transverse maxillary deficiencies with a significant indirect effect on the mandibular arch.