Miniscrew placement on mandibular buccal shelf and infra-zygomatic crest area: A finite element analysis

This study investigated the optimal placement of mini-implants in the mandibular buccal shelf and infra-zygomatic crest regions using finite element analysis.

Three-dimensional finite element method (FEM) models of bone and mini-implants were created. In the mandibular buccal shelf (MBS) region, mini-screws were positioned at three sites: between the first molar roots, between the second molar roots, and distal to the second molar, tested at two depths (4 mm and 8 mm) and two angles to the occlusal plane (60° and 90°). In the infra-zygomatioc crest (IZC) region, mini-screws were placed between the first and second maxillary molars and adjacent to the mesiobuccal root of the second molar, at depths of 7 mm and 11 mm, and angles of 40° and 75° relative to the occlusal surface. The force of 200 g was applied as immediate loading and in a vertical direction to the center of the miniscrew.

In the MBS region, the distal second molar site at 8 mm depth and 60° angle exhibited the lowest von Mises stress, while the lowest strain occurred between the first molar roots at the same depth and angle. In the IZC region, the best biomechanical response was found at 7-mm depth between the first and second molars at a 75° angle, with the highest stress occurring near the mesiobuccal root of the second molar at 11-mm depth and 40° angle.

These findings suggest that for optimal biomechanical performance, MBS mini-screws should be placed distal to the second molar at 4-8-mm depth and 60° angle, and IZC mini-screws between the first and second molars at 7-mm depth and 75° angle.