Surface and bulk properties of dental resin composites after solvent storage

Objectives. To investigate the surface micro-hardness and the diametral tensile strength (DTS) of bulk-fill and conventional resin-composites after storage in food simulating solvents. Methods. Eight materials were investigated. For the micro-hardness measurement, Teflon mould with an internal dimensions of 10 mm and 2 mm (n = 15). For the DTS measurement, Split stainless steel moulds were used to make disk-shaped specimens of 6 mm diameter and 2 mm thickness (n = 15). Materials were subdivided in to three groups (water, 75% ethanol/water and MEK). Micro-hardness measurements were made under a load of 300 gm with a dwell time of 15 s at 7, 30, and 90ds after storage. DTS was measured after 30ds at a cross head speed of 0.5 mm/min. Results. The storage time and type of solvent had a significant influence on the micro hardness. MEK showed more drastic reduction in the material micro-hardness with an exception of G-aenial universal fib (GA-F) which showed similar results in water/ethanol and MEK. DTS values of materials stored in water ranged from 48.7 MPa for the GA-F and 30.6 MPa for Ever X posterior (EXP). Generally, the results are observed to decrease with increasing solvent power, except for GA-F. Significance. Bulk-fill materials showed no superior results compared with the other materials. For the bulk-fill materials that are designed to be used as a base, their penetration by the solvents may be shielded and thus the changes observed in this study may not be of clinical importance. (C) 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.