Repair Bond Strength of Aged Composite Resins Using Different Surface Treatment Protocols

Area of Science:

• Dental Materials Science
• Restorative Dentistry
• Biomaterials Engineering

Background:

• Composite resins are widely used in dental restorations.
• Aging can compromise the integrity and bond strength of composite resins.
• Effective repair protocols are crucial for extending restoration longevity.

Purpose of the Study:

• To evaluate the shear bond strength (SBS) of thermally aged composite resins after repair using various surface treatments.
• To compare the efficacy of different surface preparation methods, including sandblasting, acid-etching, and roughening, combined with universal adhesives and silanes.

Main Methods:

• Four hundred composite resin samples (Filtek Z350XT, Spectra Smart, IPS Empress Direct, Forma) were prepared.
• Samples were divided into 10 groups based on surface treatment protocols, including controls, acid-etching, roughening, sandblasting, and silane application, before thermal aging and repair.
• Shear bond strength (SBS) was tested, and failure modes were analyzed using scanning electron microscopy.

Main Results:

• Significant differences in SBS were observed among different surface treatments and composite resin materials.
• Sandblasting protocols (dry and wet, with or without silane) yielded the highest SBS values.
• The control group (freshly repaired, no aging) showed higher SBS than the acid-etched group (G2) for most materials, while aged samples without additional treatment had decreased bond strength.

Conclusions:

• Thermally aged composite resins exhibit reduced repair bond strength without appropriate surface pre-treatment.
• Sandblasting is a highly effective surface treatment for improving the SBS of repaired aged composite resins.
• The choice of surface treatment protocol significantly impacts the bond strength of repaired composite restorations.