Effect of Different Light Curing Distances on Surface Hardness of Two Different Bulk Fill Flowable Resin-Based Composite Materials

Abstract

This in vitro study was carried out to evaluate the effect of different light curing distances (0, 2, 4, and 6 mm) on the degree of conversion and surface hardness of top and bottom surfaces of two different bulk-fill flowable resin-based composite materials (FiltekTM and X-tra base®). A total of 80 resin composite specimens were prepared in a specially designed split Teflon mold of 4 mm diameter and 4 mm thickness. They were divided into two main groups (n=40) according to the type of bulk-fill flowable resin-based composite used. Each group was further divided into four subgroups (n=10) according to light curing distance (0, 2, 4 and 6 mm). Each subgroup was further subdivided into two classes according to the surface assessed for the degree of conversion and surface hardness (top and bottom surfaces of the cured specimen). The 10 samples in each subgroup of each type of bulk-fill flowable resin-based composite was divided into two halves (n=5), half for assessment of degree of conversion and half for surface hardness. The samples were then stored at room temperature for 24 hours. Degree of conversion (DC) assessment of the tested samples was performed utilizing Fourier Transform Infrared Spectrometer (FTIR) apparatus. Microhardness evaluation of samples was performed utilizing Vickers hardness testing. Five hardness measurements were taken across the top and bottom surfaces using a 100 g load for 10 s and a mean Vickers hardness (VH) was obtained. Statistical analysis was carried out using IBM® SPSS® Statistics Version 20 for Windows.