Effect of curing method and curing time on the microhardness and wear of pit and fissure sealants

Abstract

Objective: To evaluate the effects of a light source, polymerization time and storage time on the microhardness and wear of pit and fissure sealants. Methods: Five commercial pit and fissure sealants (Fissurit F [FF], Teethmate F1 [TF], Apollo Seal [AS], Concise [CC], and Ultraseal XT Plus [US]) were used. Specimens were cured with a conventional visible light curing unit (Curing Light XL 3000) for 10, 20, 30, 40 s or with a plasma arc light curing unit (Apollo 95E) for 3, 6, 9, 12 s. The specimens were kept dry in light-shielded bottles at 37°C for 1 week, then half of them were thermocycled. The rest of them were stored in distilled water in light-shielded bottles for another 30 days, which were kept in an incubator at 37°C, followed by thermocycling. Microhardness and wear of the specimens were measured. Results: Similar degree of microhardness was achieved with the shorter curing time with the plasma arc light curing unit as with the conventional visible light-curing unit. With conventional visible light curing, the microhardness of the top surface was higher than that of the bottom surface ( P<0.05). With plasma arc light curing, the microhardness of the top surface was higher than that of the bottom surface for AS and CC, but for FF, TF and US, the microhardness of the top surface was lower than that of the bottom surface, except in the 3-s curing of US. For FF, AS, CC and US, wear in the 6 s curing with plasma arc light was similar to or less than that of the 30 s curing with conventional visible light, but for TF, wear of the 9 s curing with plasma arc light was similar to that of the 20 s curing with conventional visible light. After storage in distilled water for 30 days followed by thermocycling, there was a tendency towards a decrease in microhardness and an increase in wear. There was a significant negative correlation between microhardness and wear ( P<0.01). Significance: The tested curing methods differed significantly in their curing capacity. This study suggested that a plasma arc light curing unit needs shorter curing time than a visible light curing unit to achieve similar mechanical properties of the pit and fissure sealants tested.