Dual-cure dental composites: can light curing interfere with conversion?

Area of Science:

• Dental Materials Science
• Polymer Chemistry
• Biomaterials Engineering

Background:

• Dual-cure composites combine light-activated and self-activated polymerization for dental restorations.
• Achieving adequate depth of cure is crucial for the mechanical properties and longevity of dental restorations.
• Understanding the interplay between photo- and self-curing mechanisms is essential for optimizing composite performance.

Purpose of the Study:

• To evaluate the depth of cure of four dual-cure composites based on their light- and self-cure capabilities.
• To compare the curing performance of dual-cure composites against conventional light-cure bulk fill and universal composites.
• To investigate the influence of curing mode on the hardness of dual-cure composites at various depths.

Main Methods:

• Four dual-cure composites (BulkEZ, Activa, HyperFIL, Injectafil) and two light-cure composites (Tetric, TPH) were tested.
• Composites were cured using irradiation from one direction or allowed to self-cure without irradiation.
• Vickers hardness was measured at depths up to 6 mm.
• Statistical analysis was performed using two-way ANOVA and pairwise comparisons.

Main Results:

• Hardness significantly decreased with depth in most light- and dual-cured composites, with BulkEZ being an exception.
• Self-cured dual-cure composites maintained consistent hardness throughout their depth.
• BulkEZ demonstrated consistent hardness irrespective of the curing mode (light-cure vs. self-cure).
• Irradiation negatively impacted the hardness of HyperFIL and Injectafil in their middle sections compared to self-cured samples.
• Two dual-cure composites showed reduced hardness when light-cured, indicating interference with self-polymerization.

Conclusions:

• Dual-cure composites can achieve substantial cure through 6 mm depths, but their curing behavior varies significantly.
• BulkEZ exhibited superior performance, unaffected by curing mode, suggesting robust dual-cure functionality.
• In certain dual-cure composites, light exposure can interfere with the self-polymerization process, potentially compromising restoration integrity.
• The findings highlight the importance of selecting dual-cure composites with predictable curing characteristics for reliable dental restorations.