Bond between subsequently added light activated composite resin and hardened material

Area of Science:

• Dental Materials Science
• Polymer Chemistry

Background:

• Large composite resin restorations often require incremental layering due to limited light penetration depth.
• Ensuring adequate adhesion between sequentially cured layers is crucial for the integrity of light-activated composite resin restorations.

Purpose of the Study:

• To evaluate the effect of separate layer curing on the transverse strength of light-activated composite resins.
• To compare the mechanical properties of layered versus single-increment composite specimens.
• To investigate the influence of water contamination on the strength of layered composites.

Main Methods:

• Rectangular rod-like specimens were fabricated from four light-activated composite brands (two macrofilled, two microfilled).
• Test specimens were constructed in three pieces, with each layer cured separately.
• Control specimens were made in a single piece.
• Transverse strength was measured and compared between test and control groups.
• Water contamination was introduced during the preparation of some test specimens.

Main Results:

• Macrofilled composite specimens (layered and single-piece) exhibited comparable transverse strength, even with water contamination.
• Microfilled composite specimens showed a trend towards reduced strength when layered, particularly after water contamination during preparation.
• Adhesion between layers did not appear to compromise the strength of macrofilled composites.

Conclusions:

• Layering techniques for light-activated composite resins may impact mechanical strength, especially for microfilled materials.
• Macrofilled composites demonstrate robust performance regardless of layering or water contamination.
• Careful consideration of material type and handling is necessary when employing incremental layering for composite restorations.