Abstract
This study investigated the influence of curing distance on mu-flexural strength (mu-FS) of a nano-hybrid composite, cured using the manufacturer-recommended curing time (MCT), compared to a consistent radiant exposure (CRE) using three different light-curing units (LCUs). Beams (6x2x1 mm) were cured using the MCT or CRE with a quartz-tungsten-halogen (QTH); a single-emission-peak light-emitting-diode (SLED), or a multiple-emission-peak light-emitting-diode (MLED) LCU. Specimens were cured at 0-, 2- or 8-mm distances (n=10) and the bottom irradiance and CRE were measured using a Managing Accurate Resin Curing-Resin Calibrator spectrometer. mu-FS testing was performed, and data analyzed using two-way ANOVA and Tukey multiple comparison tests (alpha=0.05). Mean bottom irradiance was (25.4-99.7 mW/cm(2)) and CRE (0.31-1.11 J/cm(2)). mu-FS was 422.1-516.6 MPa (MCT) and 440.4-490.4 MPa (CRE). Comparing CRE to MCT showed that mu-FS significantly decreased using the CRE at 2-mm (QTH) or the MCT at 2- and 8-mm (SLED). mu-FS may be significantly impacted by the curing protocol.