Biomechanical performance of ATOZ expander: Finite-element analysis.

Introduction: Microimplant-assisted rapid palatal expansion appliances have been used for the treatment of orthodontic patients with maxillary deficiency. A new design named ATOZ (applicable from A to Z) was recently introduced to expand the scope of treatment in early permanent dentition. The objective of this study was to analyze the biomechanical performance of the ATOZ expander with various microimplants configurations using finite-element method.

Methods: Nine ATOZ models were designed based on the number of microimplants configurations on the palate. For skeletal maturation, stage B midpalatal suture (MPS) maturation classification was chosen. A displacement along the sagittal axis, parallel to the MPS, of 0.15 mm was applied on each side of the device to simulate a 1 jackscrew turn of 0.3 mm.

Results: Configurations 1, 2, 6, and 7 achieved a quasi-parallel skeletal movement with a uniform distribution of displacement in the maxilla. The highest posterior nasal spine to anterior nasal spine ratio of 95.95% was found with configuration 6, indicating an optimum quasi-parallel expansion. For configuration 2, microimplants 1 and 2 exhibited stresses of 619.18 MPa and 656.49 MPa, respectively, whereas microimplants 7 and 8 showed stresses of 609.64 MPa and 658.30 MPa, respectively. Maximum stress in zygomatic bone was 0.69 MPa. Higher stresses were more distributed in the zygomaticofrontal suture than in zygomaticotemporal and zygomaticomaxillary sutures.

Conclusions: In terms of posterior nasal spine to anterior nasal spine ratio, skeletal-to-dental ratio, and MPS deformation, ATOZ with configurations 1, 2, and 6 outperform other configurations, and thus, they can be recommended for correction of maxillary deficiency in patients with skeletal maturation of stage B or earlier.