Methods: Mandible sections of individual human cadavers (5 males, 7 females, 81±13 years, n=12) were obtained. 1.5x6mm mini-implants were inserted in the mandibles, and an environment chamber was used to maintain moisture. A constant load (2N) was applied in a perpendicular direction to the long-axis of the mini-implant for 2 hours. Creep was assessed as the change in displacement during 2 hours of loading. Maximum displacement was defined as the initial loading displacement plus creep. After removal of the mini-implant, the specimen was scanned by 3D cone-beam computed tomography (CBCT)(200micron voxel, iCAT). CBCT attenuation values of bone voxels, which correlates to TMD, were estimated surrounding the implant site.
Results: Mean value of maximum displacement was 0.052±0.034mm. The mean CBCT gray level had a significant inverse correlation with maximum displacement (r2=0.51,p<0.01).
Conclusions: A substantial amount of maximum displacement was measured. This early deformation likely amplifies bone remodeling around mini-implant interface leading to more mini-implant migration during orthodontic treatment. The CBCT based TMD measures could explain the deformation. The current finding suggested that non-invasive 3D CBCT image based TMD analysis could improve orthodontic treatment plans utilizing mini-implants.
Keywords: Bone, Digital image analysis, Implants, Mineralization and Orthodontics
See more of: Implantology Research