Mechanical stability of orthodontic miniscrew depends on a thread shape

Area of Science:

• Orthodontic implantology
• Biomaterials science
• Mechanical engineering

Background:

• Primary stability of orthodontic miniscrews is critical for successful anchorage during orthodontic treatment.
• The mechanical properties of miniscrews are influenced by their design, particularly the thread shape.
• Understanding the relationship between thread design and bone integration is essential for improving miniscrew performance.

Purpose of the Study:

• To investigate the effect of orthodontic miniscrew thread shape on mechanical stability in bone.
• To compare the primary stability of regular thread shapes versus a novel thread shape.
• To evaluate miniscrew performance under varying artificial cortical bone thicknesses.

Main Methods:

• Three types of miniscrews (Type A, B with regular threads; Type C with novel threads) were used.
• Miniscrews were inserted into artificial bone blocks with cortical bone thicknesses of 1.5, 2.0, and 3.0 mm.
• Mechanical stability was assessed by measuring maximum insertion torque (MIT), removal torque (RT), torque ratio (TR), screw mobility, static stiffness (K), dynamic stiffness (K*), and energy dissipation (tan δ).

Main Results:

• The novel thread shape (Type C) exhibited significantly higher MIT, RT, and K compared to regular thread shapes (Type A, B) in thinner bone.
• Type C miniscrews showed a torque ratio greater than 1, indicating higher removal torque than insertion torque.
• Dynamic stiffness (K*) and energy dissipation (tan δ) were comparable across all miniscrew types.

Conclusions:

• Miniscrews with a novel thread shape demonstrate superior initial stability compared to those with regular thread designs.
• The selection of miniscrew thread type should be tailored to the specific thickness of the cortical bone for optimal primary stability.
• Thread design plays a significant role in achieving predictable and stable anchorage in orthodontic treatment.