A Study on Light-cured Type II Glass-ionomer Cement for Repair

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There are some occasions in the use of light-cured glass-ionomer cements (LCGIC) when it is necessary for repairs to be made to aged restorations. It has been reported that the highest bond strength was obtained with the reduction of aged cements followed by bonding agent application. The purpose of this study was to examine the effect of thermal cycling on bond strength between aged LCGIC and newly added LCGIC using various bonding agents. Also, the flexural strength of repaired cements was measured.Two LCGICs, Fuji Ionomer Type IILC (GC) and Vitremer (3M), and five commercially available bonding agents were employed. After thermal cycling for 10,000 cycles, bonding agents were applied on the cement specimens. After surface treatment, LCGIC was condensed into molds placed on the aged cement and light activated. The finished specimens were subjected to thermal cycling for 1,000, 3,000, and 10,000 cycles to simulate the degradation occurring in oral environment. These samples were stored in 37℃ water for 24 hours, then shear bond strength test and flexural strength test were carried out using an Instron testing machine (Type 4204, Instron) at a crosshead speed of 1.0 mm/min. The results were as follows :1. Thermal cycling decreased the bond strengths between aged and newly added LCGICs. This tendency was less for the filled bonding agents than non-filled bonding agents.2. After the bond strength tests, the failure modes of the specimen made with filled bonding agents revealed mixed or cohesive failure. Adhesive failure tended to increase with increasing thermal cycles .Thermal cycling decreased the flexural strengths of repaired LCGIC.This tendency was less for the filled bonding agents than non-filled bonding agents.