The effect of pre-warming and delayed irradiation on marginal integrity of a resin-modified glass-ionomer.

Recent studies have indicated that the acid-base reactions and polymerization of resin-modified glass-ionomers (RMGIs) compete with and inhibit each other; however, external energy can also influence the properties of RMGIs. This in vitro study evaluated the effect of pre-warming and/or delayed light irradiation on marginal integrity of RMGIs in cervical restorations. Standard Class V cavities were prepared on the buccal aspects of 60 human maxillary premolars. Each cavity was treated with a cavity conditioner for 10 seconds, rinsed, and gently air-dried. An RMGI was applied to the prepared cavities as dictated by the study protocol. Group 1 samples were treated per manufacturers' instructions. Group 2 samples were photocured after a delay of 2 minutes. For samples in Group 3, the encapsulated material was pre-warmed (at 40° C) for 90 seconds; for Group 4 samples, capsules were pre-warmed and photocuring was delayed for 2.4 minutes. Microleakage scores were determined using dye penetration technique; Kruskal-Wallis and Mann-Whitney U tests were used for statistical analysis (α = 0.05). The enamel groups exhibited statistically significant differences (P = 0.036), while the dentin groups did not (P = 0.122); however, in both cases, Group 2 demonstrated the highest marginal integrity. Based on the results of this study, pre-warming could jeopardize the marginal integrity of RMGIs in cervical restorations, while delaying the curing process might improve it (particularly for enamel).