Influence of extended light exposure time on the degree of conversion and plasticization of materials used as pit and fissure sealants

Aim: To evaluate the conversion and plasticization of fissure sealer materials, as influenced by extended curing time. Methods: Twenty specimens (n = 5) of a pit and fissure sealant and a flowable composite at two curing times (20 and 60 sec) were photocured with the Blue-phase 16i light-emitting diode. The conversion was determined by Fourier transform infrared/attenuated total reflection spectroscopy 24 h after polymerization. Hardness was measured, and samples were stored in absolute ethanol for 24 h. A second hardness measurement was executed after storage to assess plasticization by the percentage of hardness decrease. Data were analyzed by analysis of variance and Pearson's correlation (alpha = 0.05). Results: The pit and fissure sealant showed lower degree of conversion than the flowable composite. The 60-sec curing time increased the conversion only for the flowable composite. Plasticization was lower for the flowable composite than for the pit and fissure sealant. The 60-sec light exposure time showed a similar percentage of hardness decrease of 20 sec. A low correlation between the conversion and plasticization was found. Conclusion: Extended curing time improved the conversion only for the flowable composite. The pit and fissure sealant presented lower conversion and higher plasticization than the flowable composite.