Constant versus dissipating forces in orthodontics: the effect on initial tooth movement and root resorption

Area of Science:

• Orthodontics
• Biomaterials Science
• Dental Research

Background:

• Orthodontic treatment frequently utilizes archwires to move teeth.
• Stainless steel and superelastic wires are common choices, each with distinct force delivery characteristics.
• Understanding their comparative effects on tooth movement and root resorption is crucial for clinical decision-making.

Purpose of the Study:

• To compare the efficacy of stainless steel and superelastic archwires in terms of tooth movement.
• To evaluate and quantify root resorption associated with each type of archwire.
• To analyze the relationship between archwire type, force delivery, and orthodontic outcomes.

Main Methods:

• A split-mouth design was employed with 84 premolars in 27 individuals undergoing buccal tooth movement.
• One side used a reactivated stainless steel wire; the contralateral side used a non-reactivated superelastic wire (0.8-1 N).
• Tooth displacement was measured using a coordinate measuring machine, and root resorption was quantified via confocal laser scanning microscopy (CLSM).

Main Results:

• Teeth moved significantly more with superelastic wires than with stainless steel wires over 12 weeks.
• While resorption lacunae depth was similar, perimeter, area, and volume were 140% greater with superelastic wires.
• Superelastic wires resulted in significantly more root resorption than stainless steel wires.

Conclusions:

• Superelastic wires (0.8-1 N) provide greater tooth movement than stainless steel wires in a 12-week experimental setup.
• The increased tooth mobility with superelastic wires is associated with significantly greater root resorption.
• Clinicians should consider the potential for increased root resorption when using superelastic wires for prolonged periods or with continuous force levels.