Resistance of mini screw to dislodgement comes from contact with:

 # Resistance of mini screw to dislodgement comes from contact with:

A. Soft tissue

B. Teeth

C. Medullary bone

D. Cortical bone

The correct answer is D. Cortical bone.

The quality and quantity of the alveolar bone are considered important influential factors affecting the success rate of orthodontic mini-implants. The cortical bone thickness is considered a decisive factor in the overall success/failure of the mini-implant. It has been shown that an increase in the cortical bone thickness in the alveolar bone of maxilla and mandible significantly increases the primary stability of the mini-implant. A recent meta-analysis showed positive association between mini-implant stability and amount of cortical bone. 

Reference: Temporary Anchorage Devices in Orthodontics, SECOND EDITION, Ravindra Nanda, BDS, MDS, PhD