Influence of dietary simulating solvents on the hardness of provisional restorative materials

Objective. To evaluate the influence of dietary simulating solvents on surface hardness of chemical, light and dual-cure provisional restorative materials. Methods. The provisional materials evaluated were Temporary Bridge Resin (TBR) (Dentsply), Protemp Garant (PG) (ESPE-3M), Luxatemp Automix (LA) (DMG), Unifast LC (UF) (GC), Luxatemp Solar Plus (LS) (DMG) and Provipoint DC (PP) (Vivadent). Materials were manipulated according to manufacturersʹ instructions and placed in customized molds. Immediately after setting/light-polymerization, the materials were stored in the following dietary simulating solvents at 37 °C for 1 week: (a) heptane, (b) 100% ethanol solution (ES), (c) 75% ES, (d) 50% ES, (e) 25% ES, and (f) distilled water. Specimens stored in air were used as control. After the one-week conditioning period, hardness testing (KHN; n=6) was carried out with a digital microhardness tester (load=100 gf; dwell TIME=15 s). Hardness ratios were plotted against the solubility parameter of the solvents and the Environmental Index was subsequently computed. Data were subjected to ANOVA/Scheffeʹs test at significance level 0.05. Results. For all materials, conditioning in the various ES resulted in significantly lower KHN values compared to conditioning in air and water. TBR, UF and PP were also significantly softened by conditioning in heptane. Ranking of Environmental Index was as follows: LS>LA>PG>TBR>UF>PP. Significance. All provisional materials were significantly softened by aqueous ethanol solutions. Materials based on bis-acryl resins were generally more resistant to damage from dietary solvent