Adaptation and Bonding of Bulk-Fill Composites in Deep Preparations

Area of Science:

• Dental Materials Science
• Biomaterials Engineering
• Restorative Dentistry

Background:

• Polymerization shrinkage in resin composites causes gaps, risking restoration longevity.
• Bulk-fill composites aim to reduce shrinkage stress, but adaptation and bond strength in deep cavities are critical concerns.

Purpose of the Study:

• To evaluate the adaptation and bond strength of a novel dual-cure bulk-fill composite in deep cavities.
• To compare its performance against light-cured and self-adhesive bulk-fill composites.

Main Methods:

• Optical coherence tomography (OCT) measured sealed floor area (SFA%) for adaptation.
• Micro-tensile bond strength (MTBS) testing assessed bonding to dentin in extracted human teeth.
• Six groups compared different bulk-fill composite types and curing protocols.

Main Results:

• The prototype dual-cure composite exhibited the lowest gap formation (SFA 91%), indicating superior adaptation.
• The self-adhesive composite showed the poorest adaptation (SFA 26%) and lowest bond strength (~21 MPa).
• Light-cured bulk-fill composites achieved the highest bond strength (~50 MPa), though with more gap formation than dual-cure.

Conclusions:

• Dual-cure bulk-fill composites offer improved adaptation in deep cavities compared to light-cured ones.
• While adaptation was excellent, the dual-cure material's bond strength did not surpass light-cured composites with the tested universal adhesive.
• Self-adhesive composites demonstrated inferior performance, highlighting the continued need for bonding systems.