Method: The white MTA (ProRoot MTA, Dentsply) was mixed and filled into the glass tube (5 mm inside diam., 2 mm height). The top surfaces of the MTA were flattened to produce the bonding surfaces. After 30 min, 1 day and 7 days of the mixing, a plastic tube (4 mm inside diam. 3 mm height) was attached with a double stick masking tape with a hole (4 mm diam.). The GIC cement (Fuji II LC, GC) was filled into the tube and light-polymerized for 20 sec. The MTA discs were kept wet in an incubator with 100% humidity before the bonding test. The dried MTA was also prepared for GIC bonding test after 1 day of the mixing. Shear bond strength test was conducted at a cross-head speed of 0.5 mm/min after 24 hours of the sample preparation. The results were analyzed by one way ANOVA (p<0.05).
Result: Shear bond strength (MPa) obtained were; 30 min wet: 1.5(±0.4), 1 day wet: 2.2(±0.3), 7 days wet: 2.1(±0.5), and 1 day dry: 1.1(±0.4). The bond strength of GIC bonded to dried MTA was significantly (p<0.05) lower than those of the wet MTA. The 30 min wet MTA showed the least bond strength compared to those of the 1 day and 7 day wet conditions. All of the MTA specimens showed adhesive failure at the interface except for the 30 min wet condition in which, all of the specimens fractured within the MTA side (cohesive failure).
Conclusion: The GIC restorative cement would be better to apply after the MTA completely set under the wet condition.