Bony adaptation after expansion with light-to-moderate continuous forces

Area of Science:

• Orthodontics
• Periodontology
• Biomaterials Science

Background:

• Dentoalveolar bone response to orthodontic forces is crucial for treatment predictability.
• Understanding bone remodeling during archwire expansion informs clinical strategies.

Purpose of the Study:

• To evaluate the biologic response of dentoalveolar bone to archwire expansion using light-to-moderate continuous forces.
• To assess tooth movement, tipping, and bone changes during expansion in a canine model.

Main Methods:

• Split-mouth design in 7 adult male dogs with passive self-ligating brackets.
• Expansion using sequential copper-nickel-titanium archwires for 9 weeks.
• Microcomputed tomography and histology to analyze bone height, thickness, and formation.

Main Results:

• Achieved 3.5 mm of buccal expansion with uncontrolled tipping (15.8°).
• Caused significant buccal bone dehiscence (reduced bone height) at mesial and distal roots.
• Demonstrated significant bone apposition on the periosteal surfaces of buccal bone.

Conclusions:

• Light-to-moderate expansion leads to tooth movement, tipping, and bone dehiscence without root resorption.
• Bone formation on periosteal surfaces suggests potential for apposition at the leading edge of tooth movement.