Temperature-dependence of creep behaviour of dental resin-composites

ObjectivesTo determine the effect of temperature, over a clinically relevant range, on the creep behaviour of a set of conventional and flowable resin-composites including two subgroups having the same resin matrix and varied filler loading.MethodsEight dental resin-composites: four flowable and four conventional were investigated. Stainless steel split moulds (4 mm × 6 mm) were used to prepare cylindrical specimens for creep examination. Specimens were irradiated in the moulds in layers of 2 mm thickness (40 s each), as well as from the radial direction after removal from the moulds, using a light-curing unit with irradiance of 650 mW/cm2. A total of 15 specimens from each material were prepared and divided into three groups (n = 5) according to the temperature; Group I: (23 °C), Group II: (37 °C) and Group III: (45 °C). Each specimen was loaded (20 MPa) for 2 h and unloaded for 2 h. Creep was measured continuously over the loading and unloading periods.ResultsAt higher temperatures greater creep and permanent set were recorded. The lowest mean creep occurred with GS and GH resin-composites. Percentage of creep recovery decreased at higher temperatures. At 23 °C, the materials exhibited comparable creep. At 37 °C and 45 °C, however, there was a greater variation between materials. For all resin-composites, there was a strong linear correlation with temperature for both creep and permanent set.ConclusionsCreep parameters of resin-composites are sensitive to temperature increase from 23 to 45 °C, as can occur intra-orally. For a given resin matrix, creep decreased with higher filler loading.