Fabrication and Characterization of Composite Discs

Five types of composite materials: Filtek Z350 (Z350; 3M ESPE, Saint Paul, MN, USA), Filtek Bulk-Fill (FB; 3M ESPE, Saint Paul, MN, USA), Tetric N-Ceram Bulk-Fill (TB; Ivoclar Vivadent, Zurich, Switzerland), Sonic Fill 2 (SF2; Kerr Dental, Orange, CA, USA), and SDR (Dentsply, Konstanz, Germany) were used for the study (Table 1). Twenty discs (10 mm in diameter and 2 mm in thickness) from each resin material were fabricated by placing the material in a stainless-steel mold and light curing for 20 s after placing a mylar strip on either side of the mold and pressing gently to remove excess material using microscopic slides. Light curing was done using an LED curing light (DemiUltra, Kerr Dental, Orange, CA, USA) that was checked frequently for irradiance values to be above 1000 mW/cm² using a digital radiometer (Bluephase Meter II, Ivoclar Vivadent Inc., Amherst, NY, USA). A2 shade was used from all materials except for TB, where IVA shade was used as recommended by the manufacturer.