Shrinkage vectors in flowable bulk-fill and conventional composites: bulk versus incremental application

Area of Science:

• Dental Materials Science
• Polymer Chemistry
• Biomaterials Engineering

Background:

• Bulk-fill composites offer efficient placement up to 4mm.
• Understanding polymerization shrinkage is crucial for restoration longevity.
• Application technique significantly impacts composite performance.

Purpose of the Study:

• To compare shrinkage vectors between bulk and incremental application of composites.
• To evaluate the impact of application method on shrinkage stress and debonding.
• To visualize polymerization shrinkage in flowable bulk-fill and conventional composites.

Main Methods:

• Micro-computed tomography (micro-CT) was used to visualize shrinkage vectors.
• Cylindrical cavities were prepared in human teeth.
• Smart Dentin Replacement (SDR) and Tetric EvoFlow were tested in bulk and incremental modes.

Main Results:

• Bulk application resulted in greater shrinkage vectors and higher debonding tendency at the cavity floor.
• Shrinkage vectors varied significantly between application groups (p < 0.05).
• Tetric EvoFlow exhibited higher linear polymerization shrinkage and shrinkage stress.

Conclusions:

• Bulk application of composites increases the risk of debonding.
• Incremental composite placement is recommended for optimal clinical outcomes.
• The study highlights the importance of application technique in composite dentistry.