Skeletal effects of monocortical and bicortical mini-implant anchorage on maxillary expansion using cone-beam computed tomography in young adults

Introduction: This study aimed to evaluate and compare the skeletal effects of monocortical and bicortical mini-implant anchorage on maxillary skeletal expansion (MSE) using cone-beam computed tomography in young adults.

Methods: The sample comprised 48 patients (aged 19.4 ± 3.3 years; 19 male, 29 female) treated with maxillary skeletal expander and was divided into 3 groups according to insertion pattern of mini-implants used. G1, 4-all-bicortical penetration (n = 17); G2, 2-rear-bicortical penetration (n = 17); G3, non-4-bicortical penetration (n = 14). Cone-beam computed tomography scans were taken before treatment and 3 months after activation.

Results: The transverse width of maxilla, nasal bone, lateral pterygoid plate, zygomatic bone, and temporal bone increased similarly in G1 and G2. Contrarily, G3 produced less skeletal expansion, having no effects on the temporal bone. Significant increases in width were seen in all 3 groups regarding transverse dentolinear measurements. A triangular expansion pattern was also observed, but G1 and G2 showed more parallel expansion than G3. In addition, G1 and G2 showed less inclination of anchorage teeth compared with G3. The loss of vertical alveolar bone, although only in a small amount, was observed in all groups.

Conclusions: MSE with non-4-bicortical penetration produced fewer orthopedic effects and more unwanted dentoalveolar side effects, whereas MSE with 2-rear-bicortical and 4-all-bicortical penetration showed similar skeletal effects, which means that 2-rear-bicortical penetrating mini-implants were critical to skeletal expansion.