The competition between the composite-dentin bond strength and the polymerization contraction stress

Area of Science:

• Dental Materials Science
• Polymer Chemistry
• Biomaterials Engineering

Background:

• Polymerization of dental composites generates contraction stresses.
• These stresses can compromise the adhesive bond between the composite and dentin.
• Understanding this phenomenon is crucial for durable dental restorations.

Purpose of the Study:

• To investigate the influence of polymerization contraction stresses on dentin adhesion.
• To compare the behavior of chemically- and light-activated composites.
• To evaluate the role of cavity geometry in bond preservation.

Main Methods:

• Utilized linear and 3-D models to simulate composite polymerization and adhesion to dentin.
• Measured bond strength over time against developing contraction stress using a tensilometer.
• Observed composite-dentin adhesion in Class V cavities representing a 3-D model.

Main Results:

• In a linear model, adhesion survived polymerization stress due to sufficient flow relaxation.
• In a 3-D model (Class V cavities), limited flow led to contraction stress exceeding bond strength, causing separation.
• Chemically- and light-activated composites exhibited similar stress-related behavior.

Conclusions:

• Flow relaxation is key to maintaining composite-dentin bond strength during polymerization.
• Confined cavity shapes significantly limit flow, increasing the risk of bond failure.
• Cavity design is critical for the long-term success of composite restorations.