Bulkfill/Layered Composite Depths Of Cure Evaluated by Solvent Resistance

Objectives: This study analyzed depth-of-cure (DOC) values of bulk-fill and layered composites based on their resistance to a solvent.
Methods: Cylindrical compules (4mm internal diameter, 12mm length) (N=5) were filled with a standard, layered composite containing CQ and TPO photoinitiators (Tetric EvoCeram (EC)) or a bulk-fill one containing CQ, TPO, and Ivocerin as photoinitiators (Tetric EvoCeram Bulk-fill (ECB)). Each specimen was photoactivated through the top of the cylinder for 20s using one of three LED sources: polywave (simultaneous exposure to violet and blue light) (BluePhase G2 (BP)), violet light only (Fusion Violet (FV)), or blue light only (Fusion Blue (FB)). Exposed specimens, along with uncured material, were retrieved and immersed in acetone, followed by 20 min of sonication. The thickness of remaining, solvent-resistant composite was measured and divided by a factor of 2, and reported as the DOC. Values were submitted to ANOVA and Tukey test for pairwise comparisons (alpha=0.05).
Results: The lowest depth of cure (2.20±0.12mm) was obtained when EC was photocured using FV (p<0.001), and the highest depth (4.31±0.36mm) was seen when ECB was exposed using FB (p<0.002). No difference in DOC was found between EC (3.09±0.11mm) and ECB (3.21±0.07mm) when using either FB and FV lights, respectively (p=0.34). When cured by the polywave LED (BP), the composites EC (2.62±0.03mm) and ECB (3.72±0.20mm) showed significant differences (p<0.001) in DOC. Exposure of composites to blue-only light emission always achieved higher DOC values for each resin tested.
Conclusions: Blue light produced the deepest cure for composites tested, even though both products contained initiators needing blue (CQ) and/or violet (TPO, Ivocerin) light, and the violet emission generated the lowest. Significant differences in DOC exist between layered and bulk-fill composites, and exposure to blue light seems to be the determining factor for obtaining high DOC values