Does adhesive thickness affect resin-dentin bond strength after thermal/load cycling?

Area of Science:

• Dental Materials Science
• Adhesive Dentistry
• Biomaterials Engineering

Background:

• Adhesive layer thickness (ADL) is a critical factor in resin-dentin bond strength.
• Understanding ADL's role under stress is crucial for long-term dental restorations.
• Two common adhesive systems (AS) were investigated: Scotchbond Multipurpose (SBMP) and Clearfil SE Bond (CSEB).

Purpose of the Study:

• To evaluate the influence of adhesive layer thickness (ADL) on resin-dentin bond strength.
• To assess the impact of thermal and mechanical loading (TML) on bond strength.
• To determine if a thicker adhesive layer mitigates TML-induced degradation.

Main Methods:

• 40 molars were prepared with flat superficial dentin.
• Adhesive systems (SBMP or CSEB) were applied in one or two layers.
• Samples underwent either 72-hour water storage or TML (500,000 cycles, 10kgf, thermal cycling) before tensile bond strength testing.

Main Results:

• Scotchbond Multipurpose (SBMP) exhibited higher bond strength than Clearfil SE Bond (CSEB) irrespective of ADL.
• Thermal and mechanical loading (TML) significantly reduced bond strength for both adhesive systems and all ADLs.
• A higher incidence of pre-testing failures occurred in the TML groups, indicating reduced bond durability.

Conclusions:

• A thicker adhesive layer does not enhance bond durability under thermal and mechanical stress.
• Both evaluated adhesive systems are susceptible to degradation from TML.
• Clinical implications suggest careful consideration of ADL and potential long-term stress on adhesive bonds.