Lee J, Kim JY, Choi YJ, Kim KH, Chung CJ. Effects of placement angle and direction of orthopedic force application on the stability of orthodontic miniscrews.
Angle Orthod 2013;
83:667-673. [PMID:
23241005 PMCID:
PMC8754024 DOI:
10.2319/090112-703.1]
[Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2012] [Accepted: 11/01/2012] [Indexed: 09/02/2023] Open
Abstract
OBJECTIVES
To evaluate the influence of placement angle and direction of orthopedic force application on the stability of miniscrews.
MATERIALS AND METHODS
Finite element analysis was performed using miniscrews inserted into supporting bone at angles of 90°, 60°, and 30° (P90°, P60°, and P30°). An orthopedic heavy force of 800 gf was applied to the heads of the miniscrews in four upward (U0°, U30°, U60°, U90°) or lateral (L0°, L30°, L60°, L90°) directions. In addition, pull-out strength of the miniscrews was measured with various force directions and cortical bone thicknesses.
RESULTS
Miniscrews with a placement angle of 30° (P30°) and 60° (P60°) showed a significant increase in maximum von Mises stress following the increase in lateral force vectors (U30°, U60°, U90°) compared to those with a placement angle of 90° (P90°). In accordance, the pull-out strength was higher with the axial upward force when compared to the upward force with lateral vectors. Maximum von Mises stress and displacement of the miniscrew increased as the angle of lateral force increased (L30°, L60°, L90°). However, a more dramatic increase in maximum von Mises stress was noted in P30° than in P60° and P90°.
CONCLUSION
Placement of the miniscrew perpendicular to the cortical bone is advantageous in terms of biomechanical stability. Placement angles of less than 60° can reduce the stability of miniscrews when orthopedic forces are applied in various directions.
Collapse