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

Background: Bulk fill composites are a new class of materials that introduced to speed up the clinical process of posterior restorations. The aim of this study was to compare the curing quality of bulk fill and conventional composites at different irradiation times and depths.Methods: In this invitro study, ۴۰ 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(۶mm×۴mm)(n=۱۰). The composites were placed and cured in bulk for each composite. For each composite, the half of samples were cured for ۲۰ second (s) using Light-Emitting Diode (LED) curing unit and irradiation time for other half was ۴۰s. After ۲۴ hours of storage in distilled water, the hardness of samples was measured using Micro hardness Tester at different depths (۰.۱,۱,۲,۳,۴ millimeter(mm)). Statistical analysis was done using Multivariate ANOVA and Independent T test (p˂۰.۰۵).Results: Both composites presented a significant reduction on hardness value with increasing depth. Tetric-N-ceram Bulk Fill showed significantly higher hardness values at all depths in both irradiation time compared to conventional composite. TNB composite did not achieve depth of cure (DOC) of ۴mm in both curing times. Irradiation time significantly affect hardness values in both composites.Conclusion: Given that neither bulk fill nor conventional composite were cured at depths greater than ۳mm, it is suggested that prolonged curing cycles be used to improve the depth of cure (DOC) of composites.

Keywords:

Composite , bulk fill , Hardness , irradiation time , depth of cure