Effects Of Different Curing Modes And Softening On A Nanohybrid-Composite

The aim of the study was to investigate the effect of different curing modes on the micro-mechanical properties of a nano hybrid-composite, previous and after softening. 

Method:

Specimens of Filtek Supreme XTE with 2 mm thickness (n=6) were cured using two high irradiance LED light curing units (Bluephase G20i and Flashmax P3) at 0 and 7-mm exposure distance. The curing conditions were: Bluephase G20i high mode 10s (Group a) and 15s (Group b), turbo mode 5s (Group c) and soft mode 15s (Group d); Flashmax P3 with (Group e) and without tip-cover 3s (Group f). The transmitted light power and energy density were measured at specimen’s bottom in real time during curing, with a radiometer. Vickers hardness (HV) and indentation modulus (E) were measured with an automatic universal-hardness indenter (Fisherscope H100C) at specimens top and bottom after storing samples for 24 hours in distilled water and softening (4 weeks in 75% ethanol at 37°C). Effects of energy density, softening, exposure distance and surface conditions were analyzed using FDR adjusted one-way ANOVA (p<0.05).

Result:

Different energy densities were observed for all groups according to distance and surface conditions. HV and E values showed significant differences for both surfaces for energy densities within the same storage conditions (p<0.05). HV and E were affected negatively from the exposure distance (p<0.05). Increasing the distance reduced E values on the top and bottom surfaces of samples for all conditions (p<0.05). After softening, cracks were observed mostly on the bottom surfaces of the specimens which were thought to be due to the insufficient curing except for Group b, d and f at 0-mm exposure distance. 

Conclusion:

Different light energy densities (8.689 J/cm² - 23.13 J/cm²), exposure distances (0-7mm) and softening influence the micro-mechanical properties of top and bottom surfaces of a nano-hybrid composite.