Creep Behavior of Resin Composite Interface Between Orthodontic Brackets and Enamel

Area of Science:

• Materials Science
• Biomaterials Engineering
• Orthodontics

Background:

• Adhesive resin creep is a critical factor in orthodontic bracket stability.
• Understanding the mechanical behavior of the bracket-enamel interface is essential for preventing treatment failures.

Purpose of the Study:

• To investigate the shear and bending creep of orthodontic adhesive resins at the bracket/enamel interface.
• To evaluate the effect of incorporating glass-fiber-reinforced composite (FRC) with different fiber orientations on adhesive creep and bracket debonding.

Main Methods:

• A bracket-tooth model (shear creep) and a three-point bending test (bending creep) were employed.
• Four bonding agent groups were tested: conventional Transbond XT (TBC), and Transbond XT with bidirectional (TBE), vertically unidirectional (TBV), or horizontally unidirectional (TBH) FRC.
• Creep compliance, nanohardness, and elastic modulus were measured.

Main Results:

• Significant differences in strain and time for bracket deflection were observed between groups (p < 0.05).
• Unidirectional fiber groups (TBV, TBH) showed statistically significant differences compared to bidirectional (TBE) and control (TBC) groups.
• The control group (TBC) exhibited the least creep compliance, highest nanohardness, and highest elastic modulus.

Conclusions:

• Incorporating glass fibers into the adhesive resin at the bracket-enamel interface increases creep and the time required for bracket debonding.
• Fiber orientation influences the mechanical properties and creep behavior of the orthodontic adhesive.