Viscosity-Dependent Shrinkage Behavior of Flowable Resin Composites

Area of Science:

• Dental Materials Science
• Polymer Chemistry
• Biomaterials Engineering

Background:

• Flowable resin composites are widely used in dental restorations.
• Linear polymerization shrinkage and resultant shrinkage stress are critical factors affecting the clinical success of these materials.
• Understanding the relationship between material properties and stress development is essential for improving restorative techniques.

Purpose of the Study:

• To investigate the relationship between viscosity, linear polymerization shrinkage, and shrinkage stress in various flowable resin composites.
• To determine how different flow characteristics of resin composites influence polymerization-induced stress.

Main Methods:

• Six flowable resin composites were categorized into low, medium, and high flow groups.
• Viscosity was measured using a cone-plate rheometer.
• Linear polymerization shrinkage and shrinkage stress were recorded in real-time after photoactivation using specialized custom-made instruments.

Main Results:

• A significant negative correlation was found between viscosity and shrinkage stress (r = -0.943, p = 0.017).
• The lowest viscosity composite exhibited the highest shrinkage stress, while a low-flow composite showed the lowest shrinkage stress.
• Linear shrinkage varied among materials but showed no significant correlation with viscosity or shrinkage stress.

Conclusions:

• Viscosity is a critical factor influencing the development of polymerization-induced shrinkage stress in flowable resin composites.
• Higher-viscosity flowable resin composites may offer advantages by reducing stress build-up during polymerization compared to high-flow variants.
• Material viscosity should be considered when selecting flowable composites to optimize clinical outcomes and minimize stress-related failures.