In vitro sliding-driven morphological changes in representative esthetic NiTi archwire surfaces

Area of Science:

• Materials Science
• Biomaterials Engineering
• Orthodontics

Background:

• Superelastic nickel-titanium (NiTi) archwires are crucial in orthodontics.
• Esthetic and functional properties of NiTi archwires are influenced by surface characteristics.
• Understanding ultrastructural changes under sliding forces is vital for optimizing orthodontic treatment.

Purpose of the Study:

• To investigate the impact of sliding forces on the ultrastructure of esthetic superelastic 0.014-inch NiTi archwires.
• To compare the surface roughness and molecular changes of coated versus uncoated NiTi archwires after sliding.
• To evaluate the influence of different bracket materials (stainless steel and ceramic) on archwire surface integrity.

Main Methods:

• Utilized atomic force microscopy, scanning electron microscopy, and light microscopy to assess surface roughness.
• Employed energy-dispersive X-ray spectroscopy to analyze molecular composition differences.
• Conducted in vitro sliding tests using a custom tensile-strength tester with four types of 0.014-inch NiTi wires (uncoated, epoxy resin-coated, Teflon-coated, Ag/biopolymer-coated) and two types of 0.022x0.028-inch brackets (stainless steel and ceramic).

Main Results:

• Epoxy resin (ER) and Teflon (TF) coated NiTi wires exhibited lower surface roughness than uncoated (CO) wires.
• Ag/biopolymer (AG) coated wires showed the highest surface roughness due to silver particles.
• Sliding significantly increased surface roughness in all NiTi wires, irrespective of bracket type.
• Wires paired with stainless steel (SS) brackets resulted in rougher surfaces than with ceramic (CE) brackets due to coating exfoliation.
• The TF-SS group demonstrated the largest roughness increase (fivefold), while ER groups showed the smallest (1.4-fold).

Conclusions:

• Sliding-induced surface roughness of superelastic NiTi archwires is significantly influenced by coating materials.
• Epoxy resin-coated archwires demonstrated superior performance regarding surface roughness, indicating potential benefits for esthetics and efficient tooth movement in orthodontic applications.