S. MARKU-COHEN , A. BEN-AMAR, S. MATALON, R. PILO (Tel Aviv University, Ramat Aviv, Israel)
Objectives: Setting reactions of Glass-Ionomer Cements (GICs) can be influenced by external factors, such as temperature. The aim of this study was to test whether thermal treatment of GICs with high power light curing devices improves their mechanical properties. Methods: Disc shaped specimens for microhardness (KHN) (3X2.5mm), compressive strength (3X6mm) and diametral tensile strength (6X3mm) tests were fabricated for: Ketac Molar Aplicap (3M-ESPE), GC Fuji IX (GC), Riva (SDI) and Ionofil® Molar (Voco)(incubated in 100% humidity). The specimens were divided into 3 subgroups: control and heating for 60 seconds from both sides with either LED – UltraLume 5 (Ultradent) or QTH - Astralis 10 (Ivoclar) curing lamps (>1000mV/cm²). The mechanical properties were tested (0.5mm/min.): 20 min., 24h, 72h and one week after mixing. Each combination of material, test, treatment and time included 15 specimens. 3 way and 2 way ANOVA was conducted for each mechanical test and material respectively.
Results: Thermal treatment with curing lamps increased surface hardness values (p<0.001) and compressive strength values (p=0.008), but does not influence diametral tensile strength. The interaction treatment time (p<0.001) for hardness shows that the main influence of the thermal treatment is evident in the half hour after material mixing (+32.3%), and the influence decreases after 24h, 72h and one week (+2-2.9%). For compressive strength the influence is +24.8% after half hour and +0.3-7.4% after 24h, 72h and a week.
Conclusions: Thermal treatment does not change the final mechanical properties of the materials compared to the control (one week), but changes the kinetics of the setting reaction in a way, that more of the setting occurs in the first half hour.