Should silane coupling agents be used when bonding brackets to composite restorations? An in vitro study

Area of Science:

• Dental Materials Science
• Orthodontic Adhesion Technology

Background:

• Bonding orthodontic brackets to resin composite (RC) restorations requires a method that ensures bracket stability under shear forces.
• Bracket removal must not damage the aesthetic integrity of the dental restoration.
• Evaluating surface treatments like silane coupling agents is crucial for optimizing bonding protocols.

Purpose of the Study:

• To investigate the efficacy of silane coupling agents in enhancing bracket adhesion to resin composite surfaces.
• To compare the shear bond strength (SBS) and failure modes of brackets bonded with and without silane treatment.
• To determine a safe and efficient bonding method for orthodontic brackets on aesthetic restorations.

Main Methods:

• Sixty stainless steel brackets were bonded to silanated and non-silanated resin composite discs using a Bis-GMA based orthodontic adhesive.
• Shear bond strength (SBS) testing was conducted using an Instron universal testing machine.
• Post-debond analysis included stereomicroscopic examination and Adhesive Remnant Index (ARI) scoring.

Main Results:

• Significant differences in bond strength were observed between the silanated and non-silanated groups (P < 0.009).
• The non-silanated group exhibited higher mean SBS (19.4 MPa) compared to the silanated group (13.1 MPa).
• Both groups demonstrated clinically acceptable mean SBS, with bond failures occurring at the bracket-adhesive interface.

Conclusions:

• Silane coupling agents do not appear to provide an advantage when bonding metal orthodontic brackets to filled resin composites.
• The use of silane agents may potentially reduce bond strength in this clinical application.
• Standard bonding protocols without silane treatment are effective for achieving clinically acceptable shear bond strength.