Comparing the Curing Quality of Bulk-fill and Conventional Composites at Various Irradiation Times and Depths

Abstract

Background: Bulk-fill composites are a new class of materials introduced to speed up the clinical process of posterior restorations. This study compared the curing quality of bulk-fill and conventional composites at different irradiation times and depths. Methods: In this in-vitro study, 40 specimens from a bulk-fill composite, Tetric N-Ceram bulk-fill (TNB), and a conventional composite, Tetric N-Ceram (TN), were fabricated using a metal mold (6 mm×4 mm) (n=10). The composites were placed and cured in bulk for each composite. For each composite, half of the samples were cured for 20 seconds (s) using a light-emitting diode (LED) curing unit, and the irradiation time for the other half was 40. After 24 hours of storage in distilled water, the hardness of the samples was measured using a microhardness tester at different depths (0.1, 1, 2, 3, and 4 mm). Statistical analysis was done using multivariate ANOVA and independent t test (P ˂ 0.05). Results: Both composites presented a significant reduction in hardness value with increasing depth. TNB showed significantly higher hardness values at all depths in both irradiation times than conventional composite. TNB composite did not achieve a depth of cure (DOC) of 4 mm at any of the two curing times. Irradiation time significantly affects hardness values in both composites. Conclusion: Given that neither bulk-fill nor conventional composite was cured at depths greater than 3 mm, it is suggested that prolonged curing cycles be used to improve the DOC of composites.